woody

It was some kind of fibre packing originally, I just use silent sport wool for mine

I guess you can if you don't remove the clutch but if the engine is unknown then I would be replacing the mains as a minimum which means clutch off and a complete strip in which case, when you split the cases the shafts will stay in the RH case. That is the case that you also reassemble into when putting it back together. You'll need to buy or improvise a puller to remove the tapered fit sleeve from the crank that holds the clutch cush drive assembly. These can be a very tight fit and difficult to remove. When you split the cases do it very gently to keep all the shafts in the RH casing as if they fall out they have shims on both ends and you need to make a note of which shim goes where to make reassembly easier. You don't want them all over the bench / floor.They aren't just on the two gear shafts, they can be on the selector drum too and they are also on each end of the kickstart shaft. They are also on the crankshaft.

As above replies, silver. The old Ford Silver Fox colour used in late 60s early 70s is a very good match as they weren't a bright silver colour. They don't look good they are done bright silver

That could almost be a cut up Sherpa alloy tank/seat unit ... The way the fins are cut on the cylinder makes it look more scrambles orientated as that was more in line with what they did than trials. It's a later engine due to points in the side, not distributor. Check the engine number as it will say what it is, C15, B40 etc in the prefix. If it's C15 and the letters SS or just S follow then it's a sports / scrambles motor which means big valve head and sports cam - not good for trials. It it has F or G it's a road engine which are ok if standard and not messed with. If it's T it's a trials engine but that's going to be unlikely

Another possibility - Steve Goode. He's reasonably knowledgeable on Cottons, probably hasn't anything himself but may know sources for Minarelli parts A real long shot is Vale-Onslow in Birmingham, they used to carry parts for just about everything in the 70s and still have stock from then. I'm not sure how hard they'll try to look for stuff but maybe worth a try

Have you tried Paul Powell at Cotton Owners. They have Minarelli parts http://www.cottonvilliersspares.co.uk/

You can get these from TY Offroad as I saw them on the stand at the Telford show, I think he has them in his development TLR. From what I've been told they work well http://www.tyoffroad.co.uk/

It fits ok to the 199b air filter hose and as they all use Bing carbs those bikes should be fine You'll need the step down inlet rubber from the cylinder as you would with a Mikuni etc as the Bing is a bigger diameter than other carbs. In Motion sell them

All the same on those I've had, the bigger pistons are used to keep boring out the 325 so if they were different they wouldn't work effectively (I'd guess)

I can't be sure but it would explain why the 159 I owned and the one my mate owned had a much quicker pick up than any other model I've ridden. The only one that comes close is my 198B which also has a Pursang type weight on it. The 159 we had made our other mate's 151 feel docile by comparison. From the 159 on I don't think the engines changed much. As the porting seems the same on all of the 159 on 325 / 340 barrels, and I can't see the slight differences in the exhausts having such an affect, the only reason I could think of was lack of weight. Unless it was done by smaller ports in the crank case mouth and crankcase compression?

I've compare the porting of a 199B, 199A and a 159 and they were all the same. If there is a difference, I missed it. The 159 is more aggressive due to the lighter clutch weight. Fit a 250 ignition flywheel and clutch weight to the 199A or B and either will spin up everywhere

The big difference between the 250 and 325/340 is the pulling power of the bigger bike which can use 3rd where the 250 can't (not often needed and probably never in today's classic trials anyway) The 198b actually picks up and revs up quicker than the 340, again, due to a light clutch weight. They'e all got enough power, 250 / 325 / 340 If you're looking for OKO carbs at Telford watch out for copies. Google OKO copy to see the difference. Even the box is a give away in the way the writing wraps around the corner at the bottom. On the copy the writing is set further to the right, so less 'text' on display on the front of the box. Plus the genuine OKO doesn't come with spare jets (the jets are different in the copy as well) If your Bing is set right and not worn out, you're not going to notice any difference with the OKO or anything else

The 92 has a lot of raw power and pulls like a train. It isn't more aggressive than later bikes but it is a lot harsher in feel with more vibration,later motors are smoother. The 159 is aggressive due to the light crank weight. As the 183 and 191 are virtually the same bike I'd guess they are too but never ridden one of those.

I use a 28mm on the 325/340 engines that had a 28mm Bing originally. Mikunis work fine if you can jet them but they are a pain in the a*** to jet (for me) If it isn't jetted right when it comes it's a lottery what to change if it's the mid range that's out due to the endless needle / needle jet combinations they have. I've found the OKO is almost right as it comes on virtually everything I've fitted it to and just needs minor change to pilot and needle position. If both are jetted right then I doubt either is better than the other - apart from the price This is the one I use http://www.ebay.co.uk/itm/OKO-28mm-RACING-CARB-FLAT-SLIDE-CARBURETTOR-CARBURETOR-/301495710655?hash=item46328b73bf and one of these http://www.ebay.co.uk/itm/SET-10x-SLOW-JETS-Tuning-PWK-Arreche-OKO-Carbs-LOW-SCTZ-/262647291462?hash=item3d26ff9e46

I'm being perfectly honest when I say I can't tell any difference between a 199, 199a or 199b power delivery. The 159 I had was much more aggressive than any of those - due to the Pursang type weight on the clutch

They run virtually out of the box on any bike. Generally the most you have to do is alter the pilot and move the needle one notch, can't remember which way or what pilot I've used (somewhere around 45 maybe) but it may be in the forum somewhere. A box of pilot jets is pretty cheap in the 32 - 50 range which you could order with the carb.

The clutches can be a bit finicky to set up as people try for a light pull on the lever which can lead to them slipping. All you had to do (I appreciate you wouldn't have known) was take the cover off and wind the adjusting nuts in one turn which would probably have sorted it. The other thing to check first though, is that the arm isn't sticking in the timing cover. This can happen if a bit of grit or grime has got in there and when you release the lever, the arm doesn't fully return meaning the clutch hasn't fully engaged. It's not apparent that this is happening when it does. To confirm, pull and release the clutch lever, then reach down and see if you can push the arm further back. If you can it's sticking and you just need to remove it and clean the housing out so it moves freely. If it isn't sticking just adjust the clutch spring tension as mentioned previously If you search this forum for clutch set up there is plenty written on how to do it from scratch. Also, when starting a Bultaco get the kickstart to the point where it engages and push hard, don't kick or thrash at it. The clutch can slip on the kickstart but that is ok as it won't when riding but you need to get the right starting technique to avoid it slipping on the kickstart

Scooter Assassins in Taiwan sell genuine OKO for around £60 and free post

11/39 is standard gearing but it is a bit high (for me) I run 11/42 or 43 which is about the same as 10/39. But you can't get a 10 tooth front sprocket here

To fit the triangular head steady you also need the T bracket that bolts to the head and these are a different size for 250/350 because of stud spacing

As long as you've released the bleed nipple enough it should back bleed with a syringe no problem. I did one a couple of weeks ago. Messy job though. If you have one of those alloy bleed nipple/banjos, I'd recommend you junk it for a proper steel one as the banjo sheared off on mine as soon as soon as I tightened the nipple

Ignition side or clutch? Any ignition flywheel will swap as long as it's from a Sherpa. Pursang looks the same but won't work as I've tried one, I think it was the timing that was different but a long time ago now. Clutch flywheels are different shapes and some may foul the inside of the later 199 style casing, get one from a 250 that has the same casing to be sure. Some models had the really light, thin clutch weight, an M159 motor I have has one

You could well be right Stan, I'd assumed, probably incorrectly now you mention it and reading the post again... that it was the little barrel he meant wasn't touching the pushrod

Might sound daft but make sure you have the cam on the right way around, should be evident from the contact marks - also make sure it isn't bent or mis-shapen (unlikely) Or: A ball bearing sits between the two pushrods - sounds like it's missing With the timing cover off, pull out the pushrod, then prise out the pushrod seal as there is a gap behind the seal that the ball bearing may have previously fallen into if someone has tried to feed it in with the seal in place. If you feed the ball bearing in from that side you need the seal out to ensure it has actually gone into the pushrod housing. Worth a look before you search for another to fit if it is missing

The jubilee clip is a 'user fix'... You just clamp a jubilee clip to the shaft spline on the right side of the engine to stop the shaft sliding to the left.