woody

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

The centre gasket is the same for all of the MARs, they just removed some material from the casing surface to accommodate the bigger crank, the stud spacing is the same Your brake cable looks like a MK2 version which is a bit longer than a MK1 cable although it will still work. Rear wheel also looks like a MK2

They are copies of the original style for the M49 and 80 Sherpas, the chrome steel stays are the style fitted to later model Sherpas and as you say, a lot stronger

You don't mention what's wrong with the fork action but when you rebuild, 180cc max of 10W fork oil is a good benchmark, start with 160cc and add a bit as necessary. These old forks won't damp very well if you use thinner weight oil

The fitted wheel looks in good shape so no point changing it for the sake of it really. The older type wheel is a heavy lump of a thing fitted to bikes from 66-73 but it may have varied slightly in design through the model range even though they all look the same, I'm not sure, so finding the correct brake plate may be tricky. Hub diameter, brake shoe width may vary etc. I'd leave that one in myself, I have that type wheel in my own 49

That's a small rear sprocket which will make the gearing very high, standard gearing is 11/46 on a 520 chain. It looks like a later wheel with conical type hub is fitted along with later forks and yokes. Shock top mounts have also been re-positioned slightly lower and forward and gussets added in front of them (not criticism, just observation) You might want to consider re-routing the wiring out of the casing bottom and move it higher to the front as on later bikes as there is always a chance it could get crushed between the bashplate and engine and break with a hard hit on a rock (common on Ossa MAR)

Yes, the engines were removed by the importer and the bikes sold as kits to avoid purchase tax. The frame and engine numbers couldn't match to qualify as a kit so frames and engines were mixed when they were sold which is why they never have matching numbers up to the point purchase tax was abolished in 1973. From then on they were sold as complete bikes so numbers would have matched from new

If you mean the picture on this page, the seat unit isn't located properly and is too high at the front. The flares at the back of the tank should line up to the top of the seat unit. The seat unit you have looks like a new item and they need 'dressing' in places to fit properly. It may not have the recess cut out that sits over the boss at the rear of the tank as the seat unit holds the back of the tank down. You may also have to shave a bit from the inside edge of the panel to clear the air filter hose. If you had the later bike you'd also have to remove material for clearance for the top shock mounts as they only sell one side panel for all series of M49

As you're in the UK the only place I think you will get rings from now in the UK is In Motion but I don't remember what sizes they have left. You may have to try abroad for rings. Join the vintage Ossa group on facebook and ask on there if In Motion can't help

The rod you're holding is a pushrod. There should be two pushrods in the Ossa with a ball bearing inbetween them. If you only have one that's the problem, it's not long enough to engage with the clutch on the other side of the engine. There should also be a seal in the end of the final drive shaft that the pushrod passes through, it might be there but I can't tell from the picture but if the pushrod just falls out it's either not there or so worn it needs replacing as the friction from the seal should stop the pushrod just falling out The standard bore is 72mm with 72.20, 72.40 and 72.60 oversizes, so maybe the 4 you can see is 40 for +40 oversize. You should be able to source rings from somewhere