woody

It sounds as though you've bought MK2 brake shoes if you've had to reduce the width to make them fit as the MK2 and later bikes use wider shoes than the MK1 Use the old shoes and have them relined with modern linings, oversize and then have them machined down to achieve full contact with the hub This is the nut for the 10T but you only want 10T if you like really low gearing, unless you have 42 rear, the 10/42 is not too bad https://www.inmotiontrials.com/product/mar-tr80-gripper-front-sprocket-tab-nut/

You'll need the specific case bolt for centre bottom of the casing as later casings use that bolt as the oil drain rather than a drain plug

The spring as shown in the picture is fitted correctly Are the pawls located properly in the selector plate? Remove it and check they haven't dislodged. When you fit them ensure that they are both held in position by the flange around the edge of the plate and clear of the gaps in the flange The gaps enable them to flick out and engage in the selector drum once installed. When the pawls are located properly, if you hold the plate in the position it will be fitted to the engine the peg on the selector will be roughly 2 o'clock (possibly 10 o'clock, depends which way the peg is pointing when you locate the pawls. Fit it in this position which will keep the pawls located and then move it to about 12 o'clock. There is some free play so it will move either side before the pawls engage in the slots in the drum. Then you should be able to just push the selector shaft in locating the spring either side of the peg in the crankcase and the slot should line up with the peg on the plate

159 is a pin type hub, I've not seen one with the threaded type.

The 15mm was measured to the inside edge of the basket teeth which is the closest surface to the case edge. Measured to the inner edge of the actual basket drum, yes that's 29mm You spacer looks correct to me as they don't sit flush up to the seal and if the chain. The positioning of everything else looks correct in this photo as well The way the hub sits in the basket looks ok from the pictures, so at the moment I'm stumped as to why there is a problem with the case fit The inner surface of the basket, which the hub sits against. Is this a completely flat surface or is there an inner recess into which the hub locates? Have you tried just fitting the hub onto the shaft on its own (it won't go all the way onto the shaft) and fitting the case? Is there clearance then? Try fitting the case (both cases) without the hub or basket and check the fit and see whether the splines on the gear shaft are fully visible which will at least eliminate a case issue, but as far as I'm aware there aren't different dimensions in that area for any of the cases

For info, dished sprockets are available new as 44T, works ok with 11T front. Original gearing was 12/46 on MK1 MAR (yours ) and 11/42 on MK2 onwards. You'd really only want a 10T front with a 42 rear. There is a specific nut you can buy for the 10T sprocket which has a shoulder on the inside to space the nut and prevent the chain catching it The wiring is old and brittle, if you leave it at the original angle where it exits the case it may well crack open the insulation and short out. Many bikes have been altered to run the wires out by the front engine mount, you're not devaluing it by doing that Brakes can work quite well if you have modern linings fitted to the shoes in oversize and then machine them down to fit the bub for maximum contact. EBC and Newfren are that thin on their linings that you barely get an inch of contact when the brake is operated

Springs are 24mm If the weight is fully home on the crank and the chain line to the basket is ok, then that should eliminate the basket and spacer as a problem, if either was wrong the chain run would be out. Which brings us back to the hub. Is it definitely fully home in the basket bearing with the back of the hub right up against the basket. I'd remove both from the engine and just seat the hub into the basket and make sure it is going fully home. Sometimes they are tight and won't push fully home by hand and need a sharp tap Something that can happen (if the clutch plate order is drive plate first) is that a drive plate can stick to the basket when plates are removed as probably most people do the same thing when removing the plates which is grab the tabs of the inner most plate and remove the pack as one - it's possible for the first drive plate to remain stuck to the basket. If the hub is then removed and the basket left in situ, the drive plate can slide downwards in the basket and if the hub is refitted it prevents the hub from fully seating. This is a proper long shot but it can happen

The top hat came with the 159 engine that I have so I assumed it is the correct one. So are you saying the basket isn't fitting far enough on the shaft and the chain run isn't in line? I'm not sure where you are now You could have the wrong basket, the engine I have in bits didn't have a basket with it. The inside edge of the cover plate should sit just inside the edge of the basket fingers I have two engines with the clutches exposed at the moment, a 199b and a 151. As a guide, on both of them, the gap between the crankcase edge and the inner side of the basket teeth is 15mm If you shorten the clutch spring studs you will never compress the springs enough to fit the pins and clutch action would be seriously heavy. That's not the way to go, there is a fundamental problem somewhere. Previous owners could have done anything to this engine over the last 40 years

Are you saying the basket is positioned too far to the right or asking if it could be? As you mentioned before that the chain run from basket to crank sprocket was in line, but if the basket is positioned to the right the chain run would be off if the crank weight is fully located, so not sure now if your saying the basket is to the right or asking if it could be The extra balls could be there for any reason really as it's impossible to know what someone has done in the past but yes, the basket being offset would offset the whole assembly. There are different length pushrods so that's another possibility, too short a pushrod I'd have to check on an engine, which I don't have one in bits at the moment, but I think It is only the basket (specifically the basket bearing inner race) that sits against the spacer. The hub pushes into the basket bearing but I don't think the end of the hub goes as far as touching the spacer so if the basket is too far to the right then the hub will be also, bringing the pins closer to the case. Is the bearing located properly in the basket. There is a circlip that retains the bearing, if that is missing has the bearing moved outwards which would push the basket towards the casing, but then I'm not sure if the hub would bind up when fitted and tightened Does the top hat definitely sit right up against the gearbox bearing? Remove the oil seal and just fit the top hat to get a better view Try fitting the top hat, then position the crank weight and basket with chain onto the shafts without the hub and push the basket against the top hat, turn it to tension the top of the chain and check the chain run Some pictures of the parts might help

Only one ball and that goes between mushroom and pushrod, but maybe the wrong pushrod is fitted and is too short. However, even if the overall length of the rod and balls is too long it can't affect the position of the spring studs as they are fixed on the hub which is not affected by the pushrod, If you leave the basket and plates off and just fit the hub and spacer, nothing else, what happens with the casing then?

A bit baffling this... If you fit just the hub and spacer, nothing else and then try and fit the casing what happens? The top hat spacer should fit inside the seal and up against the bearing, the hub then fits up against the spacer. Is there anything stopping the spacer locating against the bearing?

I've got a 159 hub in a box of bits so measured it as follows, overall depth 43mm, depth of the hub where the plates sit 22mm. depth of the boss at the back 21mm. Pin length 33mm, length of pin showing from edge of hub to end of pin 19mm. Behind the hub is a top hat distance piece that sits between the bearing and the hub. This is 13mm. These are also the measurements for the same parts fitted to model 80 and model 151. As far as I know, the hubs with the pins to hold the springs are the same on each of the Sherpas that used them, model 80 up to 159 type engine. Not sure about Pursangs though, they may be different Is the top hat behind the hub the right length. Later engines with the threaded pins have a longer top hat although if one of those was fitted it might affect chain alignment. Also some hubs with threaded pins are a few millimetres longer in depth Again, as far as I know all of the cases are the same in that area, the case shouldn't be a problem with the pins EDIT - I've just realised my use of the term pins might be confusing. By pins I mean the long studs that the springs and cups slide over, not the small roller pins that hold and tension the springs. I should have just said studs...

The model is as you've said, a 198A which is a 1979 model 250 (actually 238cc) No bottom frame tubes and alloy bashplate is correct for this model Rear mudguard loop has been cut off to copy the mod that Comerfords did to the bikes of supported riders at the time, although the bolt on mudguard brackets weren't, that is something a previous owner has done Rear wheel looks Honda. It's not unusual for the bearing housing on the brake side to break up or the chrome to peel off the braking surface in the hub on the Sherpa wheel which maybe why it's been replaced. Or, someone has fitted it so they can have a wheel with a right sided brake so that a right hand pedal can be linked directly to the brake with a rod, although this one has a badly done cable link. With the normal Sherpa wheel a right hand pedal needs a cable to the brake arm which isn't always popular, so some owners use a Yamaha, Montesa or Honda wheel instead to move the brake to the right

That's a TR77 exhaust complete

The damper rod itself is a loose fit in the alloy spacer that sits inside the bottom of the chrome stanchion, so even if the spacer has fused to the stanchion the damper rod should still move being a loose fit inside that spacer. However, the piston on the top of the rod is steel and although the entire rod assembly is not a tight fit inside the stanchion, maybe there is corrosion around the piston?. If the cone shaped bump stop is removed from the bottom of the damper rod, the rod can be removed by sliding up and out of the top of the stanchion ( in ordinary circumstances) leaving the alloy spacer in the bottom as that part will only come out of the bottom. As you seem to have nothing to lose now I'd remove the bump stop, screw a bolt into the damper rod and give it a whack with a hide mallet and see if it will force it loose and up through the stanchion. The spacer can then be tapped out through the bottom taking care not to break the shuttle valve which may still be in there and which are very brittle as I can't remember if that can be removed through the top of the stanchion or only the bottom

Your bike, a model 221, is a 175cc. The Sherpa 125cc is a model 185 and has a bore of 54mm The model 221 uses a 250cc engine which is sleeved down to 175cc so you can use a 250 piston and bore it back to 250 if you can't find the 61mm oversize piston

On ebay now https://www.ebay.co.uk/itm/Ossa-MAR-and-TR77-reproduction-mudguards-in-opaque-polypropylene-as-original-fit/233641745938?hash=item3666221e12:g:1DMAAOSwpUlfAzqt

If the engine is still together, when you split the crankcases do it carefully and try and keep the gears located on the shafts with the shafts still located one of the halves (r/h side I think from memory) If it's like the 247 Cota (I think it is but it's been years since I split one) some of the gears run on individual rollers (three per gear) They are different lengths and If they fall off the shafts and onto the bench when you split the cases you won't know which has come from where. Being careful also means any shims will stay in situ on the shaft or stay stuck to the bearing face so you can refit in the same place when reassembling as Feetupfun mentioned (same for crank shims)

I'm not technically qualified to comment on the virtues or otherwise of the NJ bearing although it sounds a whole lot of hassle to use, but what's wrong with the usual 6205 C3 ? I had 6205 C3 in my 360 Pursang when I was racing one and there were no issues

The green guards are Gonelli and they are quite short. Originally used on '78 Bultacos. Positioning the rear guard so that the rear end is in the right place means that the front edge only reaches to just under the seat so you need a second lower guard to get a full length. The original Ossa guards fitted up to the black framed TR77 were full length, not sure about the length fitted to the green TR77 as they inevitably broke so I've never actually seen an original in one piece... The translucent rear guards from In Motion are longer than the Gonelli guards

In Motion use chains sourced in the UK, they are waiting for the supply chains to open again following lockdown I think France Trial Classic are out of stock also

Several possibilities, float height, sticking float needle, dirt in the float needle housing, float needle worn Replace the float needle anyway with a new rubber tipped needle Never leave the fuel tap on with a Mikuni, they are a pain in the a*** for flooding, even when brand new. The aiirbox will have fuel in it if the front of the bike was raised, usually it runs into the engine and sits in the crankcase

I can only guess at what happened but with the electronic ignition, if it is installed in the correct position and with the flywheel located on the key, the engine will run with the stator set at any of the positions on the small allen bolts. However, the standard setting is as it comes, you just bolt it on, set the flywheel on the key, connect the wires and the engine will run If you don't use the key the flywheel can go on in any position and it is just luck if it is positioned correctly Condenser is only required for points, not the electronic kit

Why do you think that ? The key is needed otherwise how can the flywheel be positioned in the correct place. The ignition comes pre-set for the flywheel positioned on the key. I'm assuming you have the back plate positioned correctly with the 'T' at the top (coil should be on the left as you look at it) If the flywheel is completely out of position at 180 degrees out it will still produce a spark, but won't fire the engine. If you're not using the key it sounds as though the flywheel wasn't positioned correctly when it wouldn't start but after you altered the timing (assuming by moving the stator on the small allen bolts) it seems likely that when you re-fitted the flywheel you got it somewhere about where it should be so the engine fired. With the electronic ignition, with the flywheel correctly seated on the key you can set the stator in any of the available positions on the back plate and the engine will run on all of them, so altering the timing by moving the stator is a red herring and not the reason it's now running I'd reset the stator to the position it came as, ensure the 'T' on the back plate is at the top and refit the flywheel on the key to give correct timing. It should run no problem like thiis

Plonker is the MAR. Timing can be personal choice but min / max would be 2 - 3.5mm BTDC