woody

Just happens I have these which I took for someone else a while ago. No idea if they are better or not. You also need to make the T shaped bracket that fits between the two rear head studs as the bottom head steady mount bots to this

There are generally two clutch / crank flywheels on the Sherpa engines, a big thick single weight on the 250 and a bigger double weight on the 325/340. The smaller and thinner single weight fitted to the 198b may be offset on the ignition side by using the heavier ignition flywheel usually found on the 325/340. When they built the 198b they were probably scraping the bottom of the parts bins and using whatever was left. I also have a '76 325 motor which has a small weight like the 198b but it uses a double row primary chain and clutch basket. I think the thin single weight originates from the Pursang.

From what I've seen of them and from what is fitted to my own, that seems to be the usual size flywheel that was fitted to the 198b As for what it does to the engine, I haven't finished rebuilding mine yet so never ridden it, but you need to ride it for yourself as everyone's perception of good/bad is different. Easy enough to fit the bigger weight normally fitted to the 250 if you don't like it though.

The person at the VMCC who did most of the dating work isn't there anymore, so it may take a bit longer to get things processed with them

You're much better off phoning them you know, the web site just shows that they sell pistons. If they haven't an 83.25 in stock they can get them

They've been modified by smoothing them out, helps them rev a bit more I think. In smoothing them out like that it also means a little metal is lost from the edges so they end up a little oversize. Normally the cylinder would be matched to them. My modified 199b is similar as is a mate's 199a that he recently stripped for a rebuild. Standard Ossa MAR ducts are like that

From your picture, the spring tensioning nuts are wound pretty far in and so is the pushrod adjuster. It could be the clutch needs re-setting as it could have too much tension on the springs to release properly. If you search the Bultaco forum for clutch adjustment or setting up clutch etc. there have been previous topics with good info on how to do it correctly. It's possible to get a Sherpa clutch to work with quite a light one/two finger pull on the lever.

Try John Collins at Port Talbot, JC Motorcycles. Used to be a Bultaco dealer, knows a lot about them and has a stash of used parts. May have some suitable forks. It sounds as though someone has probably damaged a fork in the past and replaced it without realising there are differences. One of the the problems of 40 year old dirt bikes.... You never know what they've been through.

Ossa MAR fork tubes come in two different lengths and the longer ones, from '76 on are too long for a Bultaco. The earlier MAR forks are shorter and may be too short for a Bultaco so make sure you get them to measure them exactly before you buy them

I can't imagine they cast different legs so I'd assume it is the tubes that are a different length. As pointed out in the above post your frame looks correct for a 190 as does the bottom clamp. What I can't figure out is the 190 tubes shown in PSchrauber's picture as they don't look like they are from a 190... The knurled part looks as though it would sit below the bottom clamp but maybe it's just an illusion. The tube in the bottom picture looks more like a 190 Overall fork length can be shortened by fitting a longer alloy spacer on the damper rod which prevents the fork legs extending to their normal length so you could consider doing this if you found a pair of longer 350 forks. With your current forks though, if one is longer than the other, the longest can only extend to the overall length of the shortest so you would still have the correct overall length, so maybe there isn't an actual problem - unless I'm overlooking something. Or, to maintain the correct head angle with 350 forks, you could machine out the shoulder in the top yoke which prevents the forks being pushed through, then just push them through to match the correct 250 length.

Not sure how well 250 length forks would work on a 350, they were shorter because the 250 frame from '76 - '78 (up to the model 190) was different from the 350, particularly the headstock position. The bottom yoke was different as well. From the M198, they went back to using the same frame as the 350.

The forks fitted to the 250 models from '76 - '78 were shorter than those fitted to the 350 models so maybe someone has fitted a 250 stanchion at some point? I've no idea exactly how much shorter they actually are.

Just love the selector drum

The wheel is the correct one, you shouldn't have a spacer between the brake plate and fork, only a top hat spacer on the inside of the brake plate. If you have that spacer between the fork and brake plate, it is pushing the wheel too far over and will have caused the damage.

On a 190, there should be no spacer between the brake plate and fork leg, the only spacer on that side is inside the hub and it is a top hat spacer, the one in the photo isn't. It sits in the bearing oil seal, top hat side facing out and the inside of the brake plated sits against it. The bigger spacer fits on the opposite side, as it is in the photo and sits inside the oil seal between the bearing and the sleeve that fits inside the fork leg. The sleeve should stick out a few mm on the inside of the leg so that when the wheel is fitted it keeps the hub away from the fork leg, although the clearance isn't much, it sits very close. The spacer on the left in your photo is wrong for a 190, what front wheel is fitted - can you post a picture as the spindle / spacer arrangement is different for earlier bikes, has someone fitted an earlier wheel? Your front hub should be conical, if it's a full width hub it's from a much earlier model, maybe another bike. The spindle nut also should sit inside the fork leg when fully tight on the correct 190 front end. On the earlier bikes the nut is visible as it sits against the fork leg. The gouge is definitely from a conical hub, but when was it done? It looks old. A problem for a previous owner which no longer exists? Post a photo of your wheel / hub

I agree, can't remember why it was changed from having a seperate pre-unit class but it makes no sense for someone riding a big pre-unit having to compete in the same championship class as one of the lightweight 2-strokes - especially on tight fiddly sections that suit Bantams, James, Dot etc. Time to give them back their own class, even if it's poorly supported at first. Competing against similar bikes in their own class may encourage others back out. This should apply to both hard and easy routes.

Surely you can get the correct one from the US? Ossaworld Ossa Planet run by Keith Lynas - he must have one as he sells the thread repair inserts and does complete rebuilds Hogans If you use any kind of sealing paste in those fine threads you may come to regret it. In my MAR, I use the copper ring from In Motion which seals fine. If the ring starts to undo itself, wire it to prevent it.

The frames for the 250 and 350 were the same for each model year, so the '75 250 and 350 frames are the same, meaning the performance and appearance of the bike are unaffected by the change. Nothing to worry about unless you're bothered by originality - no point really on a 40 year old trials bike. Frame probably got damaged, someone replaced it. Confused by what you say about documents verifying the age though. A V5? If V5 states 250cc and numbers match the bike, someone has swapped the 250 frame for a 350 frame and actually had the log book changed - a bit of a rare deed you could say...

Memory a bit hazy but doesn't a TY250 twinshock gasket fit? I'm sure I used one at some point, although a long time ago

Definitely repairable Jim, I bent a rod on one of mine a couple of months ago (over 3 years of pretty hard use, so can't really complain) and gave them to Blai at Telford. He took them back to Spain with him, rebuilt them and sent them back. Might be worth having a word with Alan Whitton? I'll see him at the PJ1 round on Sunday, so I'll ask him anyway

Jim, In Motion are the new Magicals agent

I'd guess at not enough entries to date? There is the Exmoor 2 day classic on Easter weekend, Sunday/Monday, a long established event that gets a full house of twinshock and Pre65.. That may have taken entries from this trial, people not wanting to ride on Friday, then having to travel to Exmoor on Saturday Also, people may be away Easter weekend?

They look like the 305 forks, although a set of 303 forks I had were the same as those, but I had know way of knowing if they were the originals or not. I don;t think the 303 had the reverse damping forks, but I guess some of the last models could have had them. I phoned Bill Pye to ask him about this set up but after describing the internals, particularly the long tapered rod, he said he'd never come across anything like it - from my description that is... Looking logically, the conventional looking rod would do compression and the tapered one rebound Try and get a parts diagram for a 305 as I'm sure that's what they're from. From what I can see they look to be assembled correctly

Marzocchi forks vary a lot from bike to bike and even Fantic to Fantic, especially the 305 Fantic which had compression on one leg and rebound on the other. Yours could be 305 from your comment about two different set ups. Best option is to photograph them and post on here. Someone may recognise which model they are from.