woody

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

It's been a long time since I saw chrome as good as that on a Bultaco hub Have the shoes relined with modern material and have them done oversize so that they can be machined down to fit the hub for full contact. Off the shelf shoes like Newfren / EBC have quite thin linings and only a small patch of the shoe actually contacts with the hub. Villiers Services or Safetek can reline your shoes For engine, I've just tried RHT engine paint which is resistant to petrol and gives a nice finish, I got it from ebay. PJ1 used to be a popular paint with a nice finish but petrol melts it faster than boiling water takes butter of a knife now, they've changed something to meet emissions probably. Some people use barbecue paint but I'm not sure how well that resists petrol

I can't see how it can be effective. The middle silencer has a perforated tube and packing around it. The packing can get soaked or clogged with oil and carbon meaning it no longer absorbs the sound, or the packing could have completely disintegrated and have been blown out leaving an empty chamber. Caustic soda won't fix either of these, the only fix is to cut the silencer open and replace the packing after ensuring the holes in the tube aren't blocked. Same for the lower part of the back box which is also perforated tube with packing. The only place it could have any effect is in the rear box of the rear silencer which is all baffles but as these rarely clog (I've never seen a clogged one) I doubt there would be any benefit If the bike is noisy it's the packing that needs renewing

That's the correct size for the trials seat although not the correct cover, the back end was supported by resting on the mudguard. Can't help with the Alpina version, never seen one

My two, one needs rings, the other mains, plus a complete rebuild on a mate's bike hat's been standing for about 30 years and must have had a hard life in the first 10

I'm rebuilding 3 199B engines at the moment. One looks as though it has never been apart before, the pushrod in that is 185mm. The rods in the other two are 187mm....

I'm not aware there was / is an alloy tank for the M49 but Holtworks make an alloy tank for a Pursang which looks the same apart from not having the small flares at the back which line with the seat unit and a seperate breather as they use the cap. It also has twin fuel taps but just blank one off

As Naichuff said, crank,clutch and output shaft. Of the the two larger, one goes on the crank clutch side, the other on the output shaft. The smaller goes on on the mainshaft behind the clutch basket. Each of them sits in a groove in the sleeves that are on each of those shafts There is a blog here that someone did for a model 80 rebuild and he has a model 80 parts list. This will show you where the O rings are on the engine parts diagram as they fit the same on the M92 http://ralphsbultaco.blogspot.com/2014/04/12-download-parts-list.html