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Garage Diary : Sunbeam Motorcycle resto's..

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For Sale - £5,450


1955 Sunbeam S8.   Black with hand applied gold stripes. Unwarranted mileage.

Frame number : S8-8290   Matching engine and gearbox numbers.

My history with this motorcycle ..which called ‘Hovis’ ( like the traditional bakery advert) :

I bought this motorcycle in November 2011 from the following advert :


“Offered is a 1955 sunbeam s8 in good condition having been fully restored by Stewart Engineering in 1992 very little use since covering just 265 miles the last tax disc is 1994 although still in very clean condition it does require some jobs now before being roadworthy again the rear axle spindle requires replacing or re-tapping the fuel tank requires pet-sealing the exhaust is only placed on loosely.”

The bike came from a Mr John Milne, Stoke-on-Trent, in Staffordshire.  According to DVLA records I am this bike’s third owner.  Clearly the bike had been restored some time before I bought it, as it was in very-fair condition, albeit unused for the previous 18 years.  The front mudguard is fibreglass, but all other parts are correct. This includes the often incorrect tool box and air filter cover.  NB. I include an un-restored steel mudguard with this sale.  

At that time I had another Sunbeam S8 ‘Nudge’ and two other motorcycles, and I never used this one. My intent was to restore this bike while I rode another, and then to swap and ride this Sunbeam while I restored my other.  Accordingly, the motor was rebuilt through the following months - please see photos.

The engine rebuild included..

New parts from Stewart Engineering :

Chain - timing

Clutch - Bushed clutch pressure plate

Clutch - Ring clutch pressure plate

Bush - Half time gear

Oil scraper ring

Big end shells - set of four halves

Con rod nuts - Split pin - set 4

Rocker arm bush - set 4

Big end bolt - set 4

Big-end bolt nut - set 4

Valve guide - phosphor bronze - set 4

Oil pressure relief valve

Gasket set - Full engine / gearbox

Copper Cylinder head gasket

Gasket set - Drive unit

Seal - rear main

Seal - dynamo cap

Engine breather mod (with vent)

Sump extension


Plus, from other sources :


The pistons are good condition used-parts with 7.2:1 compression ratio.

new Hepolite  piston rings

new Fibre washers

new assorted fastenings.

new assorted o-rings

new Spark plugs

new HT leads

Engineering / machining

was done by Stotford Engineering Ltd., including :

All parts dissembled, inc Head.

Clean and Aqua-blast all castings.

Remove & check valves & seat's condition

Mains bearing made to fit (Phosphorous Bronze)

True (& tolerance-fit) big end shells, including re-trueing con-rod ends

Re-bush ohc pillion gear

Regrind rocker spindle

Rocker spindle bushes to match

Oil pump - skim to min. tolerance

Lighten flywheel (4 lb)

Other work done included :


Removing forging flash and rough grinding off rocker arms and con-rods

Additional clearance around the timing chain tunnel

Various thread-inserts 

Re-facing all gasket faces

Modifying the gauge oil filter to take a modern disposable element type

As a Design Engineer (subsequently retired) - I did these modifications myself and reassembled the whole with great care - for myself.!    

But then in September 2012  Nudge’s motor started to rattle badly ! ..sounding as if the big-end had failed. The sump was dropped on that engine and this was found to be the case.  So the easiest thing to do was to put the recently rebuilt engine into Nudge, and then I could rebuild the engine from Nudge  at my convenience.  It is still waiting !  NB. I did not use Hovis’ gearbox.

Subsequently, (until last month) this engine was used in the frame of my Nudge my daily commute.   On this Sunbeam I holidayed down to Dorset, travelling just for fun from across country my home in Suffolk - without going on any motorway or dual carriageway.  Unfortunately, the following year I was made redundant and I took the opportunity to retire early.  As a result I had had no commute !  That engine has done about 2000 miles since it was rebuilt. 

Far less fortunate than being made redundant is running out of money.  And so I need to let Hovis go to a new home.  To do this I first wanted to refit its original (but now rebuilt) engine. And so this was the first part of the bike’s reconditioning.

What have I done, re. this recommissioning ?

Refitted the engine and its gearbox (matching numbers) into Hovis’ frame.

Addressed an oil weep from the camshaft front cover.

Correctly set-up the engine mounts

Topped up engine, gearbox and rear-drive oils.

Corrected an ignition misfire (caused by previously incorrectly fitted HT leads)

Adjusted the carburetion (I run the carb a little rich while running-in and now that this is done I could drop the needle one notch).

Rebuilt the forks with new seals & oil.

Replaced the steering's head-race bearings for new

Replaced the drive-shaft seal into the rear drive

Dismantled the driveshaft to clean and properly re-grease its spline

Replaced the gearbox input-shaft seal

Cleaned out and sealed the fuel tanks with POR-15

Chemically cleaned the petrol filters

Replaced the fuel tap's sealing-corks

Reworked the bike’s electrical wiring, correcting faults and re-wrapping the insulation, added wiring security. I corrected the

   length of wires and used soldered connectors.

Added two additional earth leads and a fuse holder.

Fitted x2 gel batteries

Correctly adjusted the brakes, front and rear.

Replaced the headlamp reflector and bulbs for new.

Rechromed the handlebar levers.

Regreased brake linkages, drive shaft UK, and other frame parts. Lubricated other linkages and cables.

So Hovis is now back together and running.  But I’m waiting for the DVLA (registration document) to be changed, firstly to reflect the motorcycle’s ‘historic vehicle’ tax rating of zero.   The DVLA already recognize that this age of motorcycle is exempt of  MOT but to change the tax rating - the vehicle needed to be taxed for road use.  This was sent off almost two weeks ago and I am awaiting their convenience.

Note I do not know this motorcycle’s original registration number. A previous owner, possible in 1992, must have sold that (reallocate to another vehicle) and so the DVLA issued  ‘HVS 655’ as an 1955 (age related).   Aside from the new number not being transferable I’ve never had issues with this, not least because Hovis is a great name for a 1955 motorcycle. 

The dual seat is now unusual on these bikes as the standard specification was a single sprung saddle.  However a huge number of Sunbeams were so modified by owners in the 1950’s and 60’s because at that time motorcycles were daily transport for couples.  I’m not sure but, I believe Sunbeam even offered the dual seat as an option.  

Personally I find the sprung single seat a much softer ride and more comfortable for my tall stature, but I quite like the looks ..and the space under the seat is really very useful for a small-bag or wet-weather gear.    

I must emphasis, this bike is not concourse. And in particular the paint on the tank is not very good, and some of the chromework leaves something to be desired ..but from just two or three paces away - it does look smart, and would make a fine bike to simply ride and enjoy.  And if the buyer is looking for an investment, then a motorcycle in lesser cosmetic condition may be systematically improved.  I’m sure that within five years  ..a paint and chrome restored Sunbeam S8 will be worth twice current prices.  

So that’s it.  Hovis  is now For Sale at £5,450

My intent is to ride a 100 miles on the bike before it goes, just to ensure that all is safe and sound. And of course I’m awaiting the DVLA to do their thing.  

more photos < here >


- - -

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after just three days.. I had one proposal (an email offer-in-principle, as he hadn't been to see, kick the tyres, nor see how much more he could knock the price down to).  That was £1000 less than my asking price ..which I politely declined.  And then another enquirer, asking about the condition of the chrome-work - which I spent a fair amount of time answering honestly ..and then never even had a symbolic acknowledgement or thank-you in reply.  Is it any wonder that some of us really do prefer cars and motorcycles to people !?


Now after seven days, my classified listing on e-bay has had 664 views and has 41 watchers.  It's also on CarandClassic with who knows how many visits ..but no-one else has been in contact.  :(  I had hoped this Easter holiday might have been opportune timing to list this bike.  Oh well ! eh.? 


During this past week or two, I've been shamelessly distracted with schoolboy dreaming of a possibly next project (an older sports car), which I've promised to myself  IF  I sell three motorcycles and the Citroen Ami-super.   Well actually I'll go for it if I sell just one of the four ..but I'll not allow myself to play with new toy until they are ALL finished / prepared and on the market.  Not having a wife I have no-one to be mean to me ..but myself !  :twisted:  


So, I'm presently back to working on Katie, my early (1948) Sunbeam S7.,  which had been restored before I had her, but not well finished and never really sorted..  But., more about that anon - because the oven's just gone ping to tell me the pizza is ready !    :P

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I forgot to mention, just a week ago ..in fact the day after I placed the bike's adverts., I looked out to see this . . .




.. someone waiting for me down there has a wicked sense of humour  :twisted: ..



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Following on..,  This past week I'm back to working on Katie, my 71 year old Sunbeam early S7.,  which had been restored before I had her, but not well finished and never really sorted.   I really love this bike but I have to come to terms with my not having the time to maintain and ride three motorcycles (after I sell a couple of others) and a classic car, and an old sailing boat too.  So realistically but still reluctantly - I'll also have to let Katie go to a new home.



^ For whatever reason the front brake is appalling on this particular bike. Usually the S7 models are pretty good with their 8" dia drum brakes, but not at all this one ! :shock:   The lower mudguard stay is designed to swing down as a prop to lift the front wheel clear of the ground, but when I'm working in the garage it's just as easy to just slide blocks under that stay. 



^  On all post-war Sunbeams both the front and rear wheels wheels were QD (quickly detachable).. a small tommy bar is used to loosen the pinch bolt, and a larger diameter but only 6" long tommy bar to unwind (left hand thread) the wheel's solid axle-spindle.  Aside from a slight difference in tyre size the front and rear wheels are interchangeable on the S7 model.


Of course this being a shaft drive bike - there's no drive-chain to undo on the rear, and the exhaust silencer is on the other side of the bike too - so it's all rather convenient ..for us Gentlemen motor-cyclists ;)    I really do miss this sort of common-sense design-engineering on later vehicles ..And on Citroen cars !  



^ Why this front brake was not working very well ought to be self explanatory from this piccie.  The glazing was removed with a fibre wire brush, and the inside of the drum was likewise de-glazed. You might also note how little of the shoe was glazed ..or in contact with the brake drum - so I suspect this little job might need to be done several times before those shoes are fully bedded in.



^  The problem with larger brakes is the heavy weight of drum brakes. During the 1940's it was still commonplace for even quite powerful motorcycles to have 6" front brakes (which is why on old bikes - one quickly gets into the habit of applying front and rear brakes together). On the Sunbeam, the designer - Earling Poope extensively used aluminium castings for lighter weight and effective heat dissipation in all engine, gearbox, and rear drive casings ..and for this 8" front brake's backing plate.  Now de-glazed, cleaned and with selective greasing of the cable run and pivots - this brake assembly is ready to be refitted.


^ In truth, after reassembly the brake feels much the same as it did. :(   Until those brake shoes are bedded in, their contact surface area is only a small percentage of what it should be - I'll have to be very careful when riding this bike.!


That was going to be the case anyway, because the wheels had been repainted without even replacing badly rust pitted spokes.  Oh and also that this original spec Dunlop 4.50x16 front tyre was probably bought new old stock ..in the 1960's.!  That size of Dunlop ribbed front tyre hasn't been made for donkey's years. I wonder how old the inner tubes are ? :?  That front tyre is now only appropriate for a museum piece.


I have bought a replacement pair of wheels in much better condition ..which I'll include with the sale of this bike.  But as I'll now not be keeping the bike, I'll not spend the money on having those rebuilt with new spokes, nor will I buy new tyres for road use.


I do think however - it would be prudent to swap the front wheel off my other bike (an S7-deluxe, and the original subject of this topic) for road trials of Katie8)

- - -


To have the bike starting and running well, my next job was to address its peeing petrol all over the place. Starting with the fuel taps - I could feel how loose the sliding on/off plunger petcock was, so I already knew the cork seals inside were shot.



^  Yep totally useless. Only one of the four (two petcocks, each with two seals) corks had been replaced. 



^   And the one cork which had been replaced was half as thick as it should be. ! ?


The new corks feel too hard and too big to fit into the brass bodies of the fuel taps but when soaked in boiling water for five minutes they become quite malleable.  NB. when the ends are screwed on - they don't have to be screwed all the way in. They can be fitted with just a few threads wound in, and then the rest of the thread is an adjuster to tighten the corks as they wear. 


Job done, next I addressed a purely cosmetic aspect of the fuel pipes. .



^  part of the fuel feed pipes fitted on this bike had been replaced with clear plastic tube.  And the balance piece, from one side of the fuel tank to the other, with a new replacement with an oddly shaped nickle finished part.  In my stock of used bits I found some old copper pipes which imo will look much better on a 1948 motorcycle. The balance pipe is an original piece, which at one time was chrome plated. The feed pipe I think was a home made replacement for the original braided rubber pipe. 



^ It looks as if it were off a steam engine, but polished up it looks much better than the plastic tube. 


The air filter incorporated a piece of gauze to keep larger airbourne seeds and insects out.  There is in fact dished cover to go over this ..which I'd removed to also replaced the fibre washers to the carburettor's float chamber.



^ The choke mechanism is called a 'strangler' and is operated by a simple lever out the top of the air filter. This turns a disk inside which progressively closes off the amount of of gauze opening. Beautifully simple, very effective, and actually more intuitive than the later type of carburettor choke operated by a lever on the handlebars. 


- - -


I then went on to check the bike's electrics. . I fitted a spare battery as this one's died from being left standing for years and proceeded to check the usual.


I should say that I had done quite a bit of work on this bike some four years ago.  That included tank and rocker cover off to check the oil feed to the overhead camshaft. (yes, it was very advanced for the 1940's ..let alone a production motorcycle. And even more so when one sees they used a squish combustion chamber design !). 


Anyway, as it happens the rocker spindle had been fitted back-to-front when the engine was last rebuilt, and so no oil was able to get through.  I was lucky perhaps rather than clever to have checked this, as the engine had obviously been recently (in terms of usage rather than years) rebuilt, and not used since then.  As a consequence camshaft damage was mostly avoided (just bluing of some wear faces, but phew - so close to writing that camshaft and rocker arms off !).  With that corrected and other things checked, I proceeded to adjust the ignition and got the engine running very sweetly indeed.  I then neatly rewired the bike. But because of the fuel leak I'd not since had petrol in the bike. 


And then again at the end of this February, I replaced the leaky sump gasket and adjusted the rear brakes. I posted about this in the bikeshite thread < here >.  


So, it was a bit of a surprise when I was checking the function of the warning lights (oil pressure and ignition) and the bike started ..on first kick - after standing for four years !  My reaction was : :shock:  but then : :mrgreen:  and settled to an overall : 8)    The fuel was turned off  but there must have been some left in the bowl from where I'd been checking for leaks.  The engine sounded great ..and yes the oil warning light did go out correctly and in a most timely manner.


However the ignition warning light ..perhaps better thought of as a charge light - didn't go out. :-(  ..Rowlocks. Oh well, that'll be my next task then.  As said I had rewired this bike, but four years ago.  My computer's hard drive subsequently crashed and I lost all my notes of that period, and I've forgotten what issues I had and in particular what I did and didn't do.  So my first check was to see if my wiring was correct.?



^ yep that has all the telltale signs of my having been in there stripped everything out and done again from scratch. But still I needed to pull the regulator out, to check the dynamo's charge wires, which fit into the back of it.  They were fine.  I disconnected the earth wire to the warning light (to remove any possibility that a fault might be through that) and tried again - the ammeter still reads no charging.



^ The dynamo mounts directly onto the front of the motor. Withe the stator removed you can see the armature is mounted directly onto the end of the end of crankshaft. It looks like a refurbished item. 



^ Lucas 6 volt MC 4.5 special equipment dynamo was used on the early Sunbeam S7's only.  Subsequent, and very much more prolific, models use an MC 6 (watt) dynamo which fits the same but is half as big again.   



^ yes it looks good, and on close inspection I can see no sign of damage nor loose wire. 



^ all looks good here too, it only has two brushes and the wires to those appear good. One fault common to these dynamos is that the screw block for the wiring loom connection is often mistakenly undone by owners / mechanics wishing to disconnect the wires. There's a single screw in the top which makes it look like it simply unplugs.  In fact the wires from the stator are connected to it with tiny grub screws, so if yanked off these connections get broken.   The correct way to remove the wires is not to undo the top screw, but the one into the side of this bakelite block, situated between the two wires from the loom. 


Anyway, I disassembled this and these connections were good..   But it don't work.!


That was as far as I got yesterday.


"The mystery of there being no charge from this dynamo, and its remedy are still to be unraveled"  ..he thoughtfully says to himself while quietly scratching the polished bit on the top of his head.


Happy Easter. B) 


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^ I totally concur.  They're almost Victorian in many respects, but of course far more advanced  ;)   


This afternoon I popped out into the garage with just a couple of thing to try n' fix.  The first was the petrol tank's balance-pipe had a leaky soldered joint, so a little petrol was still seeping out.  And the second was to try and 'excite' the dynamo into working. I know how to follow the book telling me how to do this but tbh I really don't understand the engineering behind it ..so if someone else can explain that in simplistic mechanical minded terms, I'd be grateful. :)


Anyways up, I re-soldered the fuel pipe (after taking it off the bike ! ) ..using my new Vortex blowtorch . .




^ I bought this set because it doesn't need me to find a lighter every time I want to use it and then because it comes with three nozzle sizes.  My old blow-torches are fine for generally heating big things up, but are neither quite hot enough for annealing copper (head gaskets and sealing washers) nor fine enough for small soldering jobs like this fuel pipe's joint.  I've read the Mapp gas is 25% hotter the propane so that should sort out my need to for cherry red copper, and then the bayonet fit choice of nozzles provide me with a very neat little flame.. Pretty cool ! ..isn't quite the right phrase to use when it comes to a blow torch, but I'm sure you get my meaning. 


NB. these blow torches have been criticized for the plastic of that bayonet connection breaking so after use I removed the nozzle and put it back into the plastic packaging and found a pipe cap to fit over the top of the torch head to keep crap out.         


It never ceases to amazing me - how having the right tool for a particular job makes things go so much easier.  Fuel pipe duly re-soldered and refitted - Success at last no petrol dribbles at all.  8)

- - -


Onwards and upwards ..to the dynamo - Charge !     :mrgreen:


I had one last inspection of the stator to see again if I might see any fault, I couldn't but had a twiddle with the wires anyway. And then I cleaned the armature ring (simply wiping it clean with carb-cleaner on a clean cloth) before refitting the stator to the bike. 



^ Started the bike and.. low and behold it worked !   albeit at what seemed to be quite a lot of revs compared to the quite slow tick-over of these bikes. ..and with the ammeter needle bouncing back n' forth as if it were enthusiastically folk-dancing a jig !  Photo above taken while the engine was spinning away at something like double the tick-over speed.  Come to think of it that's only 1200 rpm's  :mellow:




Perhaps it worked before.. but I just needed a bit more throttle ?  who knows ..and I for one don't care.  All that's important is that  IT WORKS !  I'm feeling well and truly chuffed.    Yes OK.,  I'll try swapping the ammeter for another, tomorrow  ..And if that doesn't help then I'll try swapping out the voltage regulator.  Who knows I might finally be very close to getting a second bike roadworthy and on the market.   :ph34r:    


That's it for tonight, I wish you a good'n.




p.s. I wonder., Does anyone here have any experience of selling via one of the big auction houses like Bonhams ?

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Only from hearsay.

There are a lot of different fees, even if it doesn't sell.

I knew someone who put a bike in a more unscrupulous auction. It sold for £10 more than reserve and never got as far as the block.

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^ Thanks, I didn't know that about dynamos.  I recall reading a long time ago that alternators kicked in about 1400rpm, but perhaps that was an older generation as the one on my Chrysler kicks in just over a 1000rpm.  I have no idea about dynamos aside from one worked on me bicycle when I were a lad.  Oh and that they use direct voltage rather than A.C which needs rectification.  It does seem though that dynamos are heavier than alternators. I don't know for sure if that's because of their vintage or simply because the winding for high voltage but low currant have much thinner wires.. ?

Ariel Red Hunter is a vintage 500 single isn't it ?   But yes the early S7 is a bit of a sleeper ..to be savoured.  It has a noticeably hotter cam than the later bikes and is a bit of a maverick.insomuch as it positively cries out to be enjoyed. Not at all what one might expect of a so called gentleman's motorcycle ;) ..but then there were also the 'sporting gentlemen' who seemed game for anything that was outrageous and fun !   The subsequent s7-deluxe does handle slightly better (hydraulically dampened front forks helps in that respect ..but it is soft-tuned in comparison.    

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Well I've had a great couple of weeks, and I was thinking / hoping that finally (literally after many years) things were going my way ..where things actually fall into place ..to work out as good or perhaps even better than one might reasonably hope.  Nope  :?  ..it was fantastic while it lasted, but things are going wrong with a vengeance.  ie., back to normal as I know it) where however much I try - every day presents yet another issue, obstacle, frustration, delay, unexpected bill or another bloody form to fill in   ..you know the sort of everyday things that manages to instantly and completely knock the wind out of our sail / demoralises us ..and if we men were weren't so self-conscious - might even make us cry. 

It was a beautiful day here in Suffolk, and I did enjoy a lazy day. Then this evening I thought I'd have a quick look at Katie's seemingly erratic charging.. I found another little ol' Lucas ammeter, which when tried was more stable (less needle bounce than that fitted to the bike). I fitted it properly and started the bike again. Definitely better as a meter ..but the reading was still poor. ..charging a little but not even enough to provide for the side lamps. I'd hoped the fault was with the old ammeter, but apparently it wasn't.

I'm really hoping the dynamo is not a fault because having them repaired is very expensive.

Oh well, next to try was the voltage regulator, which bolts into the back of the electrical box. It's a tight fit beside the coil and under the latch to this box, but the easiest way to check electrical faults like this is by substitution of one component at a time.  I had a number of these voltage regulators on the shelf from where I'd bought a job lot of Sunbeam bits. Three of the four I'd labelled at some time 1X, 2X  and 3X respectively,  although I couldn't remember what these numbers referred to.. The fourth one I had simply labelled 'Katie'. Clearly that was the one that was on the bike before I rewired it. It looked in good shape but for its cover was missing. Perhaps that's why I used another ?  Anyway I decided it would be the first I'd try by substitution.  

Removing the regulator on the bike and substituting this 'Katie' one, caused the fuse to blow (these bikes don't normally have a fuse but I like to fit one, and clearly did when I rewired the bike several years ago).  As I changed the fuse I could hear it arc as it touched its holder ..even though the ignition and lights were turned off. ? ?  I pulled the fuse before it blew and tried again.. Had the same.  So this regulator has a direct short somewhere..  ie. it ain't no good. 

Next I randomly picked 2X and again substituted that.  it's a pain in the arse job, even to see what you're doing - when the inside of the electrical box is painted black, as is the coil, as is the regulator itself.  At least one can hear a black cat in a coal cellar ! 

Anyway job done again - the fuse stays intact and the bike starts fine. ..but no charge at all. :(  OK I now realise this is regulator # 2 which don't ( X ) work !   There's method in my madness but I'm of that age when I tend to forget what the method was. :roll:  

I now remember systematically testing them one after the other, and marking them / putting them all together ready to be sent off as a batch for repair  (..if buying new isn't cheaper).

OK,  this quick job is becoming a little tiresome now but I'm keeping my cool.  And I do have one which I know works. That is still fitted to 'Nudge'.   Nudge at least has the common decency to be a silver coloured bike, and with an aluminium coloured coil - so I can at least better see what I'm doing as I remove the regulator.  8) 

Substitute this one for the one presently fitted to Hovis  and..,   I'm sure by now you're pretty confident in your guess of what happens next ! ?

Well, I'm equally confident - you've guessed wrong.!  Because I fitted the voltage regulator into Hovis' black electrical box, refitted the fuse,  and to check to see if that rectified the erratic changing.. I kick star...ted the bike ? 


. .


the motor's locked up solid. :-o 

I thought at first it was the gearbox's kick starter quadrant had landed on the top of a tooth rather than engaging into it.. but no. putting the bike into gear and trying to turn the rear wheel had no effect.  My mind was thinking.. impolite wording to the effect of  "..Oh my dear, I'll now have to remove the gear-box's side inspection cover. How unfortunate when things were looking up ". 

But having the front cover off the dynamo, I slipped a socket onto its central nut and tried to turn the engine via that.  To no effect.

Okay ? ?  next then was to put the bike in top gear and try to rotate the back wheel (.. determinedly !). Again to no avail. 

Next then was to try with a little* more weight behind it.  The garage is up a slight incline of concrete.  So again in top gear I tried rolling it down that slope with my daintily* leaping onto the saddle (bump start fashion) while at the same time dumping the clutch.  Result .. Nope.   He down there waiting for me  :evil: does like to influence matters.. The engine is firmly locked up.! 

I had started it a half a dozen times this evening, and the oil-pressure warning light had been going out in a timely manner, but.. it's seized or else something has broken and got wedged I do not know..  I suspect the first because I didn't hear a 'clunk' or whatever, and the bike was started rev'd to check the charging from the dynamo, and turned off.  I didn't do it but when I looked inside before - I thought the engine had been rebuild not at all many miles ago.. In short it's not run in and I've been revving it. Sure it's only been for a minute or two but still there's no air cooling when the bike is in the garage.  My best guess is that the engine is not run in at all, and a piston has seized. 


I also had some disappointing news re. another matter this afternoon  ..and then also this computer is behaving irrationally as well ..  And again ebay are really winding me up - If I ever meet the guys who run it then ,,,,,,,,,, pain ! pain !  ..And now the annoying little dog next door won't stop yapping.

p.s. can I cry now ?           

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I know nothing about Sunbeams.

I have had the occasional piston seizure just after a re -bore, when riding down the road. Grab the clutch quick!

Often frees up when the engine cools down, but sometimes melts the piston a little and sticks bits to the bore. 

If I understand your words, yours ran, was switched off, and possibly seized whilst standing?

I can see this being possible, build up of heat etc. But would expect it to move when cool.

Best of luck in tracing and resolving the problem.  

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I'd agree.  I made the mistake of blue printed one of these engines (when I first started working on them).  Everything to absolutely minimum tolerances ..ought to be good eh ?  Nope., with everything so nice n' tight the blinking thing wouldn't start.!   The internal friction of every bearing etc just acted like brakes, and particularly on a short stroke engine, and with my having lightened the flywheel as well, there just wasn't enough inertia to make it happen. I phoned up Tech Support (yes, Stewart Engineering who own the copyrights to 'Sunbeam Motorcycles' and who still supply the parts for the post-war bikes - does have such an old boy.)  and he said  "yeah that can happen with some engines"  .. 

.. " the only way you can get them to start is bump it by towing"  ..

.. " And then once it start's - it'll be fine thereafter"  

er OK !     My buddy Chris was kind enough to tow me behind his 1200cc BMW and despite it only being a 500cc with just 7:1 compression ratio (once the engine is bedded in) it nearly pulled him off his bike. :mrgreen:    But still the B'g'r wouldn't start.  We subsequently took turns kicking it over in quick succession one after the other. And then it fired, just a few splutters and stopped. After a few more dozen times it ran !  Thereafter as the man said - it started fine.  Mind you it took over 1200 miles to run that engine in ..until it felt free.  ..And during the early stages it would occasionally seize and then free off.  Half a dozen times or more perhaps..    

So it's not uncommon for this to happen, particularly as the piston's bottom skirt clearance was specified at an unnecessarily tight 0.0045" and if I recall the same for the end float on the main bearing. Indeed, engine seizing even has it's own a paragraph in Haycroft's owner's manual (..and is listed twice in that book's index !).

Never-the-less - it is a pita.

Last night I was upset ..but this morning I sorted out some other stuff out and backed up my computer files in case this one dies. And I've removed the spark plugs and poured in a few cc's of penetrating oil in each bore (yes I know that is a lot !). Now I need to go to the shops ..so it'll sit there and soak in for a while.  In fact I'll probably leave it overnight before trying again to bump it free.  No point in unnecessarily stress loads other parts, perhaps in the final drive or transmission ..or in me !  Of course if the main bearing has seized then the penetrating oil will have no effect at all.  But we'll face that scenario ..if and when..

So that's it for today,   Have a good'n. 8)


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Don't you just love selling stuff on ebay. !

Not only do half the email correspondence get bounced back by ebay as not delivered, or else simply seem to get lost, but you get this sort of thing : 

New message from: ukpaul33 (297)

Hi Peter

Not sure if there is a problem as such.....
I have seen your replies but you have not answered regarding my offer of 4700
Have you seen these mails?
I explained that I am happy to drive down to you which is about a 5 hr drive but need to know,if your happy to accept 4700 as this is my limit to feel comfortable



This was his revised offer. The first was £200 less.   Now I have tried to be polite in my replies, which he says he has seen, don't seem to be getting through. 

So I've tried again :

" Hello Paul,

What you are asking is : If I buy your Sunbeam - will you give me £1,000 back ?   ..no, well how about £800 then ?
Now just why would I be inclined to give you £800 ?  I don't know you. You are not family. Nor an old friend. Nor are you holding my wife hostage.
So just in case my : "no but I'd be willing to consider a near offer "
> " Thank you but no sorry I'm not prepared to accept your revised offer.
> I believe the bike is priced fairly compared to any other I've seen
> advertised and see no good reason to accept 15% off. "
    ..is not clear.  Let me spell it out :  NO

Thank you for your enquiry.
My best regards,

Is it just me or do you all get this sort of thing. ?  :mad: 



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its the "its a 5 hour drive for me" that always irks me,how is that MY problem!?  when i bought my Ariel,i rode over to view it on my MZ,offered him £150 less because both tyres needed replacing,he appreciated me not kicking him in the nuts and coming on time,and he delivered it for me that afternoon.

Andy "plate raper" Tiernan has three S8s for sale,all at £6250.perhaps direct him there?

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I can understand someone making an offer to see if the seller simply wants to shift it quickly with no hassle. But someone trying it on like that sort-of annoys me ..very close to the point of my being insulted, and then I'll not sell to that person anyway.  Sure, if something is amiss then it's reasonable to negotiate.  But this chap hasn't even telephoned or written to discuss the bike, ask a question, nor to ask for more photos or whatever.  Just "if I come up in my van today I can bring cash"..  Very nice having that sort of cash to hand I thinks.

Yes, there are a surprising number on the market at the moment. On CarAndClassics there's now eleven of this model to choose from ..and mine is the third least expensive. 

I didn't know Andy Tiernan was a plate raper. That bugs me in this country where classic cars and bikes record a history through their registration number.  Personally I think it should be illegal (which won't happen because the DVLA cash in on it).  However, I can understand it with his business - because the majority of his sales are to abroad where the registration number is lost anyway ..and the paperwork / history file stays with the machine. 

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copied from my posting on Bikeshite yesterday : 


HELP advice / tip / sensible or otherwise suggestion - Please !

I gotta seized engine on my old Sunbeam Katie:(   < here >

Long and short of it is : her engine was rebuilt by a previous owner but it's never been used much (brakes on the bike were awful). And so its in-line twin cylinder 500cc short stroke OHV had not been run in. But she was starting easily and running well. I've decided I need to find her a new home, and so I'm checking and recommissioning as necessary.  Presently I'm working in the garage trying to sort out issues with the 6v electrical charging system. It has dynamo charging system with voltage regulator, an in-line ammeter and ignition warning light.  Initially it seemed as if I had no charging at all.

So, the first thing I did was check the dynamo itself. It looks as if it's not long ago been fully reconditioned, but still I checked the connections and twiddled around to see if I could find a fault in the wires - All seemingly good. I then moved on to checking the wiring to and from the dynamo and its connections - again all seemed good.  However when I revved the bike the ammeter started dancing around erratically. 

So clearly the dynamo is working 'some' ..because although weak I was getting indications of a positive charge (not enough to power the lights but enough to turn off the ignition warning light). 

Next I tried disconnecting the warning light, to eliminate the possibility of a fault through that - No difference.

The following day I swapped out the ammeter.  And although the needle was less bouncy - the readings were still erratic. 


Then, I moved on to checking the voltage regulator.  Again I did this by substitution of one voltage regulator for another (I had a few in a box which I'd bought with a job lot of project bikes). Once swapped over, I'd start the bike and rev it to 1/4 throttle to see the ammeter reading.  I only needed to run it for a minute or two, for each swap ..and then the engine would cool down a bit while I swapped out for the next.  Unfortunately the first two spares I had were duds, so I was just about to try the third (..a good one taken off my other bike) and found the engine to have seized. 

This is not uncommon on these bikes during running-in (which have a couple of unnecessarily tight tolerances), but I've never had one do this before ..after a short test and while cooling down in the garage.  I hoped that leaving it thoroughly cool overnight might have thermally contracted and freed itself - but it didn't.

The following day, I tried rocking the bike back n' forth vigorously in 4th gear, but still she didn't free up. I had a can of penetrating oil which had become depressurised (..not squirty any more) so I decanted its contents into a jar ..and from there added a few cc of the stuff through each spark plug hole. That's a lot but why muck around.!  I then left that for another 24 hours.  

Today I've tried rocking the bike back n' forth vigorously in 4th gear again (until panting x three occasions) - but still no go.  Even with the cable eased right off, the clutch slips a little with such jolting.. 

The engine is seized, with the rear-cylinder valves open and the front's closed.  Feeling with a probe I gather the pistons are about half way down their bores. The piston top is wet with penetrating oil.  Nevertheless I've just added another few cc's to each.

      So there we have it my (latest) problem.  Naturally I'd prefer not to start pulling the bike apart, even to take the cylinder head off  or to drop the sump - IF someone here has experience,  a clever idea, or Tip  of how I might otherwise free it. ?   ;)

Thanks, Bfg.

- - -


On 4/24/2019 at 7:11 PM, RayMK said:

Trying to be helpful, but my experience of seizing is only with 2 strokes which, for me at any rate, have only ever run tight or seized on full throttle when riding. Apart from checking that rings have not been shredded by the ports, recovery and a return to normal running was undramatic.

Therefore, my experience leads me to be surprised that an engine can seize after an apparently normal period of running, and I assume a normal switch off.  In my ignorance of possible reasons for the perplexing 'lock-up,' I would go for the easy investigations first e.g.

1. Drain the engine oil to see if there are traces of metal - which would suggest mechanical conflict and probably warrant a strip down.

2. If possible, and with the bike on a centre stand, observe parts of the transmission when rocking the back wheel to ensure that everything is free to move (rock) up to the crankshaft.  I suspect this will be difficult or impossible because of the enclosed nature of the Sunbeam engine and transmission design.

3. With your knowledge of the engine's internals, are there any components located with a woodruff key or similar locking/orientation devices which may somehow have dislodged and caused a mechanical obstruction?  I would be looking at camshaft, oil pump and distributor drives in this context. Of course, if a possibility is identified then strip down is the unfortunate consequence.

4. If the engine has pushrods, can you ascertain by looking at them (assuming minimal dismantling for viewing access!) as to whether one or other end of a rod has become unseated and locked the engine?

That's my lot.  I think you will have to bite the bullet and strip the engine unless something obvious and fixable is found.  

Life's little troubles can be bloody inconvenient when they gang up on you.  

These motors wouldn't normally seize, but I suspect this one has literally only done a few dozen miles since it was rebuilt.  And I don't know what tolerances it was assembled to. But if they were minimum - then yes it might well pinch up ..but then usually free off just as easily. 

Most commonly the pistons' skirts seize, but if the crankshaft's end float was set to its minimum then the massive white metal bearing is a likely place for a chunk to break off and become lodged.  I've seen bearings with this damage quite often because of faulty (porous) manufacture. In my opinion those two components were unnecessarily tight (..as if a printing error in the manual !). 

Removing the rocker cover is no big deal but for removing the fuel tank first. Never the less I guess that will have to be done in any case. I've just replaced the sump gasket ..for one I made in cork, but can drop the sump again to see if I can see anything.  Who knows - if I can't see anything wrong (which would be the situation if a piston skirt was seized) then I might be able to take a block of wood to the crank and give it a wallop.!

With the rocker cover off  and the sump removed I'll be able to see the cam chain (..no push-rods as this is an OHC ) to ensure that's not snapped or its clip come undone and got itself lodged. Oh the thought of any of these things is enough to make one sweat with fear. 

I do thank you for your thoughts  ..they have bump started my thinking, with regard to what I must now face. 

All is good with the world ..somewhere.!  ;) 


- - -

Good morning, Today is a wet and grey day over here in Suffolk, which I'm sure the farmer's crops greatly appreciate.  And I'll be in the garage to lift the rocker cover off and drop the sump ..to see what I can see.  Wish me well !


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Katie :


I went out to the garage this afternoon with a little trepidation in what I might find..


I removed the petrol tank for clear access to the cast aluminium rocker cover. It can be removed with the tank in place but it's much easier when putting it back on, to see what you're doing re. cleanliness and gaskets.  Just three studs with domed nuts hold the cover on so it's not a big deal to lift it off and have a look inside. .  . 



^ looking good so far.  You can see how nice n' clean everything is ..and that the OHC timing chain to the rear hasn't come adrift.



^  closer up, and one can see that oil circulation is just as it should be - great.



^  I'd raised the front wheel off the ground for better access to the sump, and drained the oil.  Note the blue line I have up from the rear suspension mounts. This goes to a pulley and cleating block from the garage rafter, which I'm using as a steady / to safeguard against the bike from falling sideways. 



^ and this is the very shallow early-S7 type sump with it's gauze filter tinware.  This faces upwards inside the engine so any large bits of debris would sit on the top of this.  Thankfully there are no big chunks :)



And under the the gauze filter tinware : the sump was clean (but for a few bits of fluff  etc.) - I didn't put this engine together.! 


However I did check the big end shells when I started to recommission Katie four years ago. .



^ It's not the best of photos with camera resting on the floor looking up to where I couldn't otherwise see, but the split pins on each big-end caps are as I did them. - All looks fine.


So I thank God that I cannot see any sign of more than a tight piston seizing in its bore. This is such a relief ! :mrgreen:


Now all I have to do is to free it ! ??


I'll let you know how I get on.  ;)


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Blinking Fantastic !  it's free turning again :mrgreen:


Just moments before I was saying to myself " I don't know what else I can do - I'll just have to take the cylinder orf " but at the same time I was thinking, " but I can't get the piston to the top of its stroke  ..and I need to do that to get the piston and rod out ".  Having dropped the sump this is how I've been trying to turn the crankshaft . . .



^  I could feel the very slight (correct) end-float in the rear cylinder's big end shell, whereas the forward cylinder was tighter than a drum ..so I ascertained the seizure was in the forward bore.  Using timbers, one against another as levers, I knew where to focus my efforts. With exertion, working under a motorcycle on its centre-stand - I managed to push the counter-bob sideways .. to slightly turn the crank. .  .



^ I'd scratched the crank-case (blue line) and centre punched the bob-weight (blue arrow) so I could see movement. By the time I got it this far I could also see the big white-metal main bearing wasn't damaged (red arrow). That was a relief, because if it had broken up - then the whole engine would have had to be stripped and rebuilt.


After adding another few cc of penetrating oil to the forward cylinder I continued to struggle. You know I keep threatening to diet ..now I wish I had !  I'm too big for crawling under any vehicle, let alone one just 11" off the ground.  Using a short timber block against the edge of the crankshaft's bob weight ..and a lump hammer I managed to turn the crank through perhaps 80 degrees (bringing the piston downwards). . .



^ using the camera with its flash to see up towards the offending piston I couldn't really see anything amis.  


All I could do was to try and turn the crank tiny bit at a time back n' forth.  That was yesterday before I gave in for the night. 


Then we ran out of heating oil.  :-( 

- - -


This afternoon I avoided going out to the garage until after 3pm ..let's just say I wasn't very motivated.


But go out I did and continued to struggle with another short block (the first had split to pieces) and block hammer, then the longer timbers where I could get leverage. But still I couldn't get the piston up the bore.  :(  I loosened the tappet of an opening valve as far as it would go, just to ease a little pressure off. and tried again .. and again .. and again.


Exasperated, I stood there looking at what's needed to lift the cylinder head off.....  head steady,  distributor,  timing chain,  exhaust,  fuel pipes,  electrical connections,  cylinder head nuts ..including that bloody awkward one inside the timing chest ..  So I tried once again turning the back wheel while in 4th gear.! - To no avail. :(  


..and then I tentatively tried the kick start again, and it turned the crank until the piston seized again, on what is probably a small amount of residue piston on the cylinder's wall. ..But until that point - it had moved easily.!  So I crawled back underneath, levered the crankshaft bob-weight back again, and tried again.  Lo and behold it swung all the way around, without the slightest notch. I repeatedly kicked the engine over and over ..and you'd never have known there was ever an issue.!   I cannot say just how relieved I am.  Thank Goodness these Sunbeams have a wet sump, that you can drop to access inside the bottom of the engine. That alone is still quite unusual on motorcycles.


It's a good day somewhere, and today I'm the most fortunate one  :D 


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Katie's locked up again .. :evil:

I'm presently stripping her down to take the cylinder head off, so the jobs which I had thought were done are now being undone and will each need doing again. It's most disheartening  :(

One interesting tidbit I'd never before come across is that, with an overhead camshaft engine - the timing chain link is nowhere to be seen in the position the engine is seized, so I can't undo it.  Fortunately the top chain sprocket unbolts from the end of the camshaft on these Sunbeams, and there's enough space to do that and get the bolt out, so it's not a biggie - just that I'd never had that one before, nor even thought of it.

The dynamo armature was a real sod to get off ..but eventually job done.  Now I need to substitute it with the one on Hovis.  ie., to try it on Hovis - to see if it does in fact work, or else need to send it off for reconditioning.

I'll post so piccies later.




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. .

as promised I post a couple of piccies above,  but didn't get to take the cylinder head off yet,  because i spent a couple of hours substituting Hovis' dynamo with the one off Katie and tried it.   It  is charging fine. :)   ..but that armature was such a tight fit  - it took ages to get it off  Hovis again !   


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Cylinder head lifted this afternoon.

All looks good so far ..save the piston being seized in the bore. It a bit sooty in the combustion chamber but that's to be expected after having filled each cyclinder with pentrating oil and having run it (just for a few minutes) last time thing locked up.  I can't see the piston or the cylinder bore until the former is removed ..which means dropping the sump and again trying to turn the crank with timber levers.  There's no point in my releasing the big end cap yet because if I do that then I have no means to move the piston save a wooden block and a big hammer ..and even then it would go downwards and I need it to come up and out of the cylinder bore.. 

I drained the oil overnight, so now it's now time to get back to the garage and low tackle it ;)   

- - -


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Well. . .  The good news is - the piston was not seized in the bore  :)

. . .

But . . ,  the bad news is that the forward big end shells were seized onto the crank  :(

. . .


^ they are meant to be white metal bearing surfaces.  On the right hand pair of big end shells the white metal has totally worn away to reveal the copper plating underneath.  Thankfully, no damage was done to the crank's journals (..bearing surface).


The oil way through the crankshaft itself is clear.  Even so the rear bearing (left) doesn't look brilliant either.  However, the small oil feed hole in the one shell (middle in the photo above) is hard blocked with the white metal (or whatever is now used to coat the bearing face of the shell).  These holes don't lead anywhere so I don't know how significant that is. 

I did wonder if the holes were the right size (aftermarket shells or whatever ?) so I went out to the shed where I have all sorts of used Sunbeam junk ..and found another set of shells with the same size (if not slightly smaller) holes. These are Vandervell shells and I assume them to be correct. As it happens they were also badly worn.  But perhaps more interesting is that I'd marked one, in felt pen, with the letters KTO  ..this bike's registration number..  Huh ! ? .. I remember correcting the wrongly assembled rocker shaft, which was starving the camshaft of oil ..and I remember checking the big ends, dropping the caps to check these shells and then making sure the bolts were correctly torqued and the split pins were new and correct, but I had long since forgotten that I had changed the shells too..  Only now do I recall using good but used or perhaps new-old-stock shells I'd bought from a former Sunbeam expert.  I know I wouldn't have put junk ones in.  But being second hand does account for the discolouration of the back face of the above shell.

So the question I'm faced with is : why is this engine knocking out its shells ?  The shells I put in were the same +0.030" as previously fitted. And if they had been too tight then the crank would not have swung. So the shell's size is right, the oil is correct and a good brand name, and the crank is a centrifugal gallery type which I can feel is clear and cavernous.  There's plenty of oil getting up to the camshaft..  So it seems as if  I'm going to have to pull the engine out of the bike and to totally dismantle it - to check the oil way which feeds the crankshaft.. What a pisser !  

The oil feed to the crank is from the rear main-bearing (fed by the mechanical pump).  This has a gallery around it with take-off drillings to the camshaft, to the cam-chain idle wheel, to the oil pressure relief valve, and to the crankshaft.  Somehow it seems as if  that drilling leading to the crank has got partially blocked (don't look at me - I did not rebuild this engine!). Some oil is getting through, and that first feeds the rear big end shell, what's left over goes to the forward big end shell.  Oil lubricates the big ends as it squeezes out of its bearings and (thanks to centrifugal force of the crank spinning) is then flung off to splash coat the pistons' gudgeon pins and cylinder bores. 

Monday's mission impossible is to identify and eliminate the culprit blockage.    

Have a good weekend,

Bfg  :( 


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Good morning, and what a beautiful day it is too.   Below is just a quick pictorial update to what I was doing yesterday . .  


Electrical boxes moved out of the way, cables and wires disconnected as was the drive shaft, then I lifted the engine out. In this state, without the cylinder head and all the ancillaries or oil I can manage this by hand, without block and tackle. 


The early (1946 - 1949)  Sunbeam is a near extinct beast now, and almost every component was altered for subsequent production of the S7-deluxe and S8 bikes (1949 - 1956).   While I have this bike's engine out I've taken the opportunity to photograph dozens of these differences for record. The four bolt gearbox casing, its drain plug, and the rear engine mount bracket, seen above are just some of these.  In due course I'll publish these on my own Sunbeam R and R website (there's a link to that in my signature)  as a reference for others who might be restoring these bikes.


I then proceeded to split the engine from the gearbox.  The  in-series  ('S' : series type Sunbeams) twin cylinders, dry clutch, gearbox and shaft drive is pretty apparent from the above photo. And again the vented louvred cover on the bell housing, and also the clutch-enclosing flywheel assembly are unique to this model.  The latter is to prevent oil from leaking onto the clutch.  It's just so common-sense to do this when you think about it, but where else have you seen the idea.?


Unlike a car's clutch - the Sunbeam's pressure plate (lower right) sits against the clutch springs. The friction plate is centralised to slide on a spline on the gearbox input shaft, and the backing plate (lower left) is then bolted to the shouldered studs on the flywheel.  A central pushrod, activated via a lever at the back of the gearbox (see previous photo), operates against the pressure plate to compress the springs, thereby releasing the compressive grip on the friction plate.  And yes., the pushrod does go right the way through the gearbox's main shaft. 

I'll not bore you with photos of the pistons being removed, pulling the flywheel off, or the engine's rear cover, but jump forward to a photo of these bike's timing gear


This is as dismantled. I haven't cleaned anything yet.   The end of the crankshaft is the light coloured gear in the middle. To the left (which is at the bottom of the engine) is the geared oil pump with a pressure relief valve next to it.  The overhead camshaft timing gear has spokes (..lightening holes) on these early bikes.  Later types didn't have those holes and were twice as heavy.  The cam-chain and sprocket can be seen under it. 

The bolted oil-stained casting is the main-bearing carrier.  It is drilled to route oil from the oil pump into a gallery around the main bearing,  and from there to pressure feed oil to the crankshaft, the timing gear's spindle, and to the drilling up through the crankcase for the valve gear.  All oil ways are internal on this engine. Oil-return is gravity to the wet sump with its pan style gauze filter.


The main bearing carrier and crankshaft being withdrawn.


And just as I suspected - the drilling which feeds oil from the rear main bearing into the crankshaft was blocked hard and solid.   It is truly amazing that this engine ran for more than just a few minutes.  The fact that I've ridden it a few miles and presumably so did the previous owner who rebuilt it .. is a credit to the robustness of its 1940's design. 


I had to drill the crud out of the hole ..the blockage was hard and about an inch long, so not just a bit of paper towel or whatever lost inside during the rebuild.    The crankshaft itself is in part hollow, insomuch as there is a large diameter gallery, running forward to back, inside the big ends.  The (above) drilling leads oil into this chamber, which in turn feeds the big end shells and splash lubricates the bottom of the pistons and the bores.  At the other end (the front) of the gallery there's a big screw plug, to close it off.  It is part hidden by the front main bearing, but with that removed the chamber can be cleaned out.   That has happened on this engine, but the engine rebuilder couldn't have thoroughly checked the oil feed drilling.  It's a simple error to make, but the real mistake was in not checking it was clear after the main chamber had been cleared out.  A good mechanic is not only conscientious in his working standards, but also double checks things as he or she goes. 


Parts cleaner now flushing through the cavities. Clearly there is now no restriction to flow.

Now all I have to do is to clean everything up, assess the damage and rectify it, and of course put it all back together again.   Tbh though - I am feeling really very  glad, relieved, and grateful to He above.  The damage from this blockage might so easily have been much worse, and perhaps even have written the engine off ..and the bike too  if it had locked solid when under load riding at speed (these bikes do 80+ mph).    Furthermore the likelihood of finding a replacement engine does not bear thinking about,  neither does the cost I might have incurred.   phew !

Bfg.   ;)

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.. it's been a couple of weeks since an update,  so a quick pictorial for you . .


^ just a little tidying up.  The con rods on these engines are forged aluminium. It's not a performance engine so I don't worry about lightening things.  All I do is to clean up the original rough cut edges where the flash had been removed ..to lessening the hard edges where stress might start a crack from.  The pistons with a split skirt are non standard - but they fit and the bike was running well before it was starved of oil by the blockage, so they can go back in. 


  ^ a little more clearance.  The block is laid on its side on the bench and this slot at the back of the engine is where the cam-chain runs.  Inevitably at some time the chain has been slack and flapped around a bit. This cuts grooves (see arrow) which then leaves hard edges. Again I don't like epicenters for stress cracks to develop so I cut the aluminium crankcase back for a little more clearance.  (Below) 



^ it doesn't need to be smoothed out and polished.  I just cut back to as deep as the chain had worn. No more, no less.


This is one of the sump studs, which I had helicoiled a few weeks ago, but clearly it had pulled out when I tightened the sump nut.  This was a bit of a surprise because it's only a 1/4" stud that goes in there and the gasket I made is cork, so it was not very tight.   Anyway it needed doing. 


^ This is what I found..  I didn't drill it out like this.  Clearly it had been a problem for someone beforehand and they had drilled a very rough hole and filled it. I don't know what it was but possibly epoxy filler paste.  What do you do with a hole like that ! ?


^ Well I had recently bought a new blowtorch and some HS2000 rods, which are in effect a low melting point aluminium alloy.  I melted this into the hole to fill it up.  Not totally successful as you can see, because the blowtorch couldn't get the surrounding aluminium hot enough for the filler alloy to flow fully into every crevise (..after all this crank case is designed as a heat sink to dissipate heat !).  Never-the-less what is in there appeared to be tight.  


^ I proceeded with  drilling a hole for the stud, using the cast aluminium sump itself as a pattern


^ well it might not have been a pretty repair but drilling this alloy is just like drilling other aluminium.  And the 'fill' stayed in place so it can't be too weak.



^ Tapping the fill with 1/4" Whitworth for the stud also went fine. 


^ well that seems to have worked.  I added a few drops of wicking lock thread around the 'fill'  just to make sure, and when that was well dry - I filled the rough hole edge with Araldite epoxy so the gasket will have a flat to seal against.  It certainly seems as strong as any other stud now,  and at the end of the day will only be torqued to 6 to 8 ft-lb.

That'll be all for today but I do have a few other tasks done to share. 




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Thanks Captain ;) Yeah a shame ..but these things happen sometimes and most of us make a mistake or three now and then.  And perhaps we might even take a short cut ..just to get on with life.   I'm surprised only so much as the guy who sold it (so presumably rebuilt this motor) is the son of a founder member of the post-war Sunbeam club, so I might have expected more with that family's experience and enthusiasm.  hey ho !


Following on from my previous pictorial update, here goes ..


^ this is the crankshafts rear main bearing carrier. The big white-metal bearing (centre) reveals the oil route from the geared pump (bottom right) to the crankshaft drilling which was blocked. While it was off I removed drilling plugs to check and clean inside the oil galleries.   I then went on to change the incorrect nyloc nuts used to bolt the pump on.  Nylocs are not designed to withstand the hot oil inside an engine.   A rectangular section lock washer and plain nut is safest, because if the pump body loosens and lifts just a little then the oil pressure is lost. 

Another task I did has little to do with rebuilding this engine, aside from the fact that it is an early model S7 (bike # 936), and almost everything subtly changed in 1949 when the S7-deluxe was introduced.   Not all the changes were good, and most I'd guess were to reduce costs in production ..but at least the later bike had hydraulic-dampened front forks.    Anyway by way of diversion,  I took some time out to record many of these detail changes ..which at sometime I'll add to my SunbeamRandR website < here >    In the meantime here are just a couple of examples . . 


This is its gauze filter .. for when one adds  oil to the engine.   For me it's inconceivable to pour so lumpy an oil into an engine that this coarseness of mesh would stop bits from getting in.!  :huh:

Below is a visual comparison of this early bike's crankshaft versus the later type . .


The early crankshaft (left) has been machined with a flat across all three bob weights.  The later type had just the central bob machined down either side.  The bearing sizes, throw and weight of the two are the same,  but because of where the weight is taken off,  the early one would give  a slightly quicker engine response (having slightly less inertia).   However the later type has a little less mass in its central bob, which might have been to lessen crankshaft flexing or else to change its harmonics.  Although of the same dimension, the front main bearing was also changed from a ball race to a roller bearing. 

It's also apparent that its drilling for balance is about the centreline, suggesting the crank with conrods and pistons were originally balanced by hand.  The latter is drilled (for balance) on one side of the front bob weight and then right on the opposite side of the central weight, which I suspect would have evaluated by a machine.    NB. please ignore their colouring. I've simply cleaned the early one ..before putting in back inside the engine. 

Moving on.. 


^ seen upside down on the bench ; the crankshaft has been refitted complete with oil pump, the rear bearing carrier, and the OHC timing wheel with cam-chain.  



^ The back of the engine and timing gear is closed off with this pressed-steel cover.  Unfortunately they very often get bent (see edge along the top of this photo) which can only happen when kicking around in someone's garage.   Around the screw holes also get pulled into its cork gasket due to the original spec using small washers.  As the gasket face which prevents engine oil getting onto the clutch - this cover needs to be suitably flat  . .


^ work in progress, panel beating to as near flat as is practical.


^ not prefect but certainly much better than it was.  This will now seal against a cork gasket.



^ when the engine seized,  and I was trying to free it by rocking the bike (in gear) down a slope vigorously ..the clutch was slipping.   Tbh it's surprising that it wasn't slipping more.  I really don't understand why someone should spend a lot of time, care, and money rebuilding the engine,  only to then put its clutch back together in this state.  The friction plate itself is on its last mm before the rivets would start wearing away.  NB.  clutch plates from the later engine are a direct fit.  


^ a little elbow grease, that's all.


^ again not perfect,  but I replaced the friction plate, and scrubbed up the pressure plate faces, then cold-galvanize painted the surrounds to keep humidity-induced rust at bay - so again it now ought to be serviceable.



^ fortunately the bore was not badly damaged as the engine seized under no load, but the forward cylinder's piston rings were iffy so I replaced them.  Naturally I double checked the end gap on all before reassembly. 



^ all clean inside, with new big end shells ( those two pairs of  shell cost a whopping £102 + VAT ! ).   Fresh oil liberally used during assembly.  The pistons are now in and the big end shells torqued up correctly (25 ft-lb) and new split-pins are fitted, cut to short length and folded.   This is almost ready to close up ..but first I wanted to do something about the sump's oil filter

..more on that next time..   Tune in - same time.,  same channel !

Bfg ;)

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