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Old Bultaco


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post-20650-0-89352700-1415395388_thumb.jpgReceived with thanks Stuart, that will be a great help.

I am posting photos of the letters on the headstock. There were what seemed to be a series of punch marks on the side of the bottom yoke but when I stripped the paint off the other side there were the same marks in the same place opposite. Not sure what that's about as they must have been put there before painting.

On another point, would it be better to re-chrome the handlebars or fit new ones?



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Looking at the pic. my immediate thought is that the original frame was probably replaced owing to damage and the number on the replacement was obliterated by grinding and punching it out, possibly to avoid problems with the local registration authority.

I don't think this would be too unusual for a bike used off-road, and I think early Bultaco frames were apparently easily bent as well as being heavy (little more than mild steel "gas pipe", according to a frame-builder I knew).

Re chrome-plating, this would likely cost as much (or even more) than new bars, and original steel bars got bent even before frames, anyway..... unless someone knows differently, of course.

Which gear pinion is damaged - layshaft or mainshaft ?

Number of teeth. or part no. ?

Good luck with the rebuild.

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Sounds like a likely explanation about the frame Lorenzo. You're probably right about the handlebars too but I find it very hard to discard original parts- a bit daft I know, its just in my makeup. I'll give that some thought.

Its the mainshaft pinion, part no.311-004, 29 teeth (Thanks Stuart!) it broke in half.

Another question, how does one remove the steering shaft from the headstock? Soak in WD40 and assault with a blunt instrument or is there a more subtle method? Ditto the swing arm bolt.

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WD40 is virtually useless as penetrating fluid - save it for Water Displacing duties that it was designed for.

Get yourself some Plus-Gas formula A or similar and give that a try.

Regret, unable to help with the pinion.

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I have done several restorations over the years and I have myself not had a problem removing the fork yokes/steering stems. The earlier bikes may be worse as the "adjusting ring-head bearing" is steel rather than aluminium as on later bikes Soak with a penatrating oil or possibly Diesel if nothing else to hand. Clean up exposed threads with a wire brush and then as they say in the Haynes manual undoo! The spindle should be a tight fit in the bottom yoke and I have come across examples were this is loose and may rotate. If this is the case with your bike you will have an issue and will have to resort to methods best not writtain down on a public forum. The top yoke is a hard to get part but all the other bits are common to other models at the time and come up on ebay particularly in the states quite reguarly so if all else fails.............

Swinging arm spindles can also be very difficult. I restored a 125 Sherpa and had to resort to drilling the spindle out. I marked the end of the spindle and drilled a hole to just inside the frame and then increased this hole size until the spindle was in affect drilled away. Doing this both sides allowed me to remove the swinging arm. The 125 has an advantage over the M10 that it has an engine mount in the middle and I was able to/had to hacksaw through the spindle each side of this as well. When all apart I tried removing the spindle from the rear fork bearings and engine mount in a fly press and despite soaking in penatrating oil for over a week failed! I had to drill out the engine mount and make new spindle and fork bearings. Not difficult but it all took time.

After typing this I am off to the garage to start stripping my M80 engne. I had not ridden the bike for about 5 years and after two trials recently it is making some interesting rummbling noises. I suspect that the layup has not done the main bearings and big end much good. I have a big flypress and I do my own flywheel disassembly and assembly so hope to have it back running by tomorrow evening.


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I have to make clear that I have never ridden in a trial in my life so I feel a little out of place and a bit of an imposter among all of you. The chap who gave me the bike was involved and made me aware of what was involved. I used the Sherpa on my farm quite a lot for tasks that would now be fulfilled by the modern day quad. It got quite a bit of use but it became a bit of a nuisance when it became difficult to start when hot. That contributed to the broken gear as the clutch cable broke when I was down the fields and rather than stop the bike I decided to ride it home. I was going grand until I didn't get the revs right when changing down. So that was the end of that - until now. So that's my potted history.

Anyway, a bit of progress, I removed the bottom yoke and spindle, there's a bit of play in the bottom bearing. Top one is ok. It will be a bit difficult to remove the inner part of the bottom bearing as it is stuck pretty tight on the spindle but I reckon I'll get the better of it.

The rear fork spindle is putting up a fight but I am pumping easing fluid (WD40,sorry Lorenzo!) in through the grease nipple hole and have got it turning but it is fighting hard.

Excuse the rambling!

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I was looking at your markings on the frame, I rubbed my frame down today and discovered a G and a P. One on the side of the headstock one on the top frame tube. It made me think these might be identity marks from the individual welders or factory inspectors. I know we worked a similar method in Shorts. I would have stamped any jigs I worked on with a T242, that was unique to me.

The little square marks are a bit more peculiar. You say there is another set directly opposite. Almost seems like witness marks left by the jaws of a vice, although they look a bit too deep for that. Strange.



Edited by trailie
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Thanks Ralph,

Sounds a likely explanation of the headstock letters. When I found the other marks I thought it may have been a vice too but yes, they are much too deep as that much pressure would have deformed the tube. I think Lorenzo's theory is the more likely though would the frame No. be stamped on both sides?

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I have looked through images of M10's and all have the cylinder head fins aligned north, south but mine are radial as in the picture. Is this usual? I cannot find any pictures of this type of head. Perhaps its from another engine. Any views on this?

Another question about the rear shocks. Mine have chrome? sleeves on top. Were these supplied as standard? Probably unlikely to be obtainable now. Can one get the shocks without the springs? Last question, where would one get a workshop manual for the M10. You know what they say, when all else fails, read the instructions!

Many thanks in advance,


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Lar -

Yes, your bike has a standard cylinder head with radial fins, although it looks like a few may have been broken off..........

I don't know where you've been looking for images, but I simply Googled "Model 10 Bultaco" and came up with a numberseveral showing

radial fins.

Here's an example (I hope) :-

http://www.vintagebike.co.uk/pictures/1966-bultaco-sherpa-t-model-10/#.VGzV9zSsUl8 (image #3 shows fin layout clearly)

and this will possibly link to many more.


Edited by lorenzo
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As per reply from Lerenzo, Your cylinder head is correct for a model 10. They changed to front/back fins for the Model 27 but thay also changed at the same time to a new 5 speed engine. Your engine is defiantly 4 speed model 10. The 5 speed engine would not fit your frame either (engine mounts are different) so you definatly have a model 10. Your tank is also correct for a late model 10 the model 27 tank is different again.

I Can not help with the shock question. I have never seen a picture of a Bultaco trials bike with those top covers but I have a picture of a similar age Rickman Metisse Bultaco scrambler fitted with these and as Rickman were the official importers at the time thiese could be original. Try ringing Inmotion I am sure they will be able to help you with suitable replacements.

A workshop manual does not exist. Dave Renham at Inmotion does a 4 speed engine manual which is probably all you need. Any other questions I suggest you come on here and ask.


Edited by twinnshock
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Thanks to you both, great to be able to access that kind of knowledge. Tried the link Lorenzo but it wouldn't work but never mind, I'll do the Google thing. Good to know the bike hasn't been messed with.

Thanks for now lads,


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Yes, as the others have said, you have the correct engine and cylinder head for an M10 Sherpa.

The shocks with chrome top shrouds are old type Girling units (now unobtainable) which would have

been replacements for the original Betor units. As others have intimated, just replace with a modern

day equivalent (Betor, Hagon, NJB, Falcon etc, etc).

Edited by sparks2
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