woody

Just wondering why you think that.? The frame is probably an M91/92 series 2 but could be a 124/125 or 150/151 (250 and 325 from that era are the same visually so can't be told apart) Definitely not 158. The forks are M92 as is the chrome exhaust (which will bolt straight onto a 250 engine from '75 onwards)

They're both fibreglass, Ossa only fitted fibreglass at the factory. Only UK bikes had alloy tanks. The MAR alloy tank is a different shape from the glass tank, the Gripper alloy tank is the same shape but the tank and side panel are seperate units on UK bikes and the tank didn't use the front fixing bolts

You're never going to get an answer you can trust in 100%. If I was buying one I'd line it. A few years back I bought a tank for my 340 Sherpa and never got the chance to see if it was resistant or not as it split first time out along the seam where the upper and lower mouldings are joined (I think it was there anyway) The quality was poor and if held up to the light, looking through the filler cap hole you could see through the bottom in places, it was that thin. The quality of some repro parts isn't always good

They aren't engine mounts that have been removed, the lower front engine mount, where fitted (not on 5 speed trials engines) is central so where something has been removed is the wrong place for a front lower engine mount. It's possibly had case savers welded on at some point which may have been removed. Can't help with the upper mounts as I can't really see them from the pictures but the M80 doesn't have brackets there.It's nearly 50 years old so unless you know the history, previous owners could have fitted all manner of things. No idea what the G is, never seen that before, could signify the country it was exported to if not a UK bike originally?

It's not a split washer, the two halves locate in the groove in the spline and sit behind the big weight which sits up against them when tightened up. They also double up for use with the tool to remove the taper as PMK's photos show They weren't used as a part in the MAR engine so I guess they must have been available along with the puller from Ossa agents. Before you try and remove it measure the length as there are three different lengths for these. You'll need to know which one if trying to source a replacement should it break

There is a Pursang one that will do the job https://www.inmotiontrials.com/product/pursang-mk11-chain-rubber-slipper/

It's very difficult. This is only a suggestion as sometimes they come out, sometimes not. Remove the bushes from either side to allow more movement. Remove the timing cover, detach the spring from the tensioner arm and remove the pad, then you might just wriggle it out. What I did was take some off the end of the shaft on the timing side, either cut t or ground it can't remember, while still in the bike which made it a lot easier to get out. Because I'd lost enough length to drill another split pin hole I drilled and tapped the end of the shaft to 6mm so that when it went back in I fitted a bolt and penny washer instead of a split pin to stop it sliding through the bush. The same can be done to the other side once it's out but probably not necessary

Your clutch case should look like this, you can see the plug underneath https://www.ebay.co.uk/itm/Bultaco-Lobito-Pursang-Alpina-175-clutch-engine-case-cover-cap/172934687132?epid=7007483100&hash=item2843b5e99c:g:19UAAOSwnw9Z5~gd In your photo the original gearbox drain plug is the one behind the one you are pointing to, although I can't see that it has a drain bolt in it. The one you are pointing to is something that someone has added, maybe made their own gearbox drain if the original is damaged. I can't tell where exactly it's positioned but could also be a drain for the ignition should water get in there The casting on the other side is for a speedo drive which is a hangover from older engines. Thyey weren't used on later bikes, It's blank and isn't drilled

There is only one place I know of that does them and they are a repro not NOS judging by the kinks in the bend - Frankie Mountain If yours is good enough have it re-chromed as at least you know it fits properly. Some pattern parts.... http://www.frankiemountain.com/en/compra/ossa-mick-andrews-exhaust-pipe-chrome-new-ossa-mar-exhaust-250cc-1421

The UK 199a had an alloy tank. same as earlier models. The B had a different alloy tank unique to that model but it may have been supplied with the bike as an extra as there were many B models in UK with the plastic tank

4B was underneath but this is an UKR motor. Frame is MK1

Do you mean original type exhaust or original look for the bike? If exhaust, that should be easy enough as middle boxes and tail pipes appear on ebay fairly often. The best set up is from a mid 70s on Cota that uses middle and tail pipe and would have been what the Ulf Karson motor had. Nice and quiet If you mean original look for the bike, that's more tricky as would you match the look of the early bike that the frame is from or the later bike that the engine is from? To make it look like an early bike will take a lot and isn't worth it. Personally I wouldn't care as apart from many detail changes which aren't really noticeable, the look of the bikes barely changed from '72 to '76. with frame colour changes and a slimmer tank being the most obvious. The frame itself barely changed at all from MK1 to UKR apart from accommodating a right hand side rear brake lever in about '73. Yours looks to have been converted from l/h to r/h already. I think you have the best of the 247 engines with better power delivery and the slimmer casings plus clutch arm on top of casing which means they don't get caught by rocks as the earlier levers can situated underneath. You have the later hubs and yokes. If you can find a later, slimmer tank cover and alloy undertank from a '72 onwards bike, then with a silver/grey frame you'll have the appearance of a MK3, MK4 or MK4b bike or with a black frame you will have the appearance of a MK5 or UKR Cota First thing I'd do is sort the exhaust as it will make a difference to getting it running how it should, fit proper tyres and bars, decent grips levers and cables and concentrate on getting it to run right. Then do whatever with the appearance if you want to. I'd take off the alloy guards and replace with plastic as they won't last 5 minutes left on. Ok for show but not go. Last thing is the forks. I didn't look at the first photo above when I commented before as I remember the bike from ebay. However, on ebay the photo was of the other side, l/h side. Now I've looked at the one above, it has odd fork legs fitted. The r/h is from the early MK1 / MK2 bike whereas the l/h is from a MK3 onwards bike

The usual consequence was the stop retaining bolt being ripped out of the casing as it was only a short bolt. The casing could end up in any degree of a mess. This was all a bit hush hush at the time and Honda did provide replacement engines as presumable it was recognised as a design fault. Mine was replaced. The design fix I belive was fitting a longer bolt. The only other fix is by welding depending on how bad the damage is. If weld repair is possible, if casing bits have gone into the gearbox they obviously can't be left there so stripping and clearing out would be necessary

You have a very early chassis from '68 if the number is correct with a much later engine, probably an UKR from '75/76. Wheels forks and yokes from later bike also. Exhaust has had the middle box removed and re-routed to exit where it is for whatever reason. Tank unit is the earlier type from the '68 - '72 range

The B airbox attaches differently from the A airbox, so to fit one on the A frame the frame mountings need to be altered to suit the B mounting points. The B box intake is in the top and the rear A mounting point would sit right over the intake. The A sidepanel mounts also need to be removed but that's already don on this frame. I fitted one to my 198A, not sure if this link will work

It was proper carbon but a one off made a friend of the owner

I checked my Haynes and Clymer manuals this afternoon but neither give any measurements. I don't have an actual Bultaco manual but I'm fairly sure they are just parts diagrams rather than instructional

Sherpas were fitted with four different hub types and there are quite a few more for other Bultacos. I'm not sure you'll find the tolerances / measurements you're looking for in a Bultaco manual, I don't think they were that detailed. You can find some online if you google Bultaco manual

Changing is easy, drain oil, cover off and remove the springs which will be held in by nuts on your bike, not pins like earlier models. Fibre plates are obviously thicker than steel so I don't think you will get the same number of fibre plates in as steel. I use Barnett friction plates which are Kevlar and I replace 1 Kevlar plate with a steel plate to get the right pack thickness. I guess it will be the same for the other types of fibre plate. The Kevlar plates break very well when the clutch is disengaged, take up is predictable and because the Kevlar bites better than the steel the spring tension can be backed off more for a lighter pull (together with using the longer front brake arm on the clutch as they are the same spline) The spring nuts are quite deep so if you back them off too much they will foul the inside of the case and make a mess. I reduce the depth of mine to avoid that. Search this forum for 'clutch set up' or such like as there are a few posts on setting the clutch up for best operation going back over the years

Gearbox is 600cc of light gear oil such as Silkolene light or other brand equivalent If the clutch is original then the plates are all steel so you can use Auto Transmission Fluid. If the friction plates have been replaced with fibre plates then you can use ATF or light gear oil - 300cc. If you don't know whether the plates have been replaced just use ATF as it will work with either

But, a used Yamaha TY hub could be just as worn, there's no guarantee they work any better. I've ridden Yams with dire brakes as well as good. My Sherpas have decent brakes using modern shoe linings machined to fit. You could remove the lip from the hub and get the shoes relined with oversize linings, 5 - 6mm thick and then machine them down to fit. Or there is an M49 wheel on ebay now after a dealer in Norwich broke a perfectly good bike for parts - utterly criminal in my opinion wrecking a perfectly good bike like that, especially the prices they're trying to get for the parts https://www.ebay.co.uk/itm/BULTACO-250-SHERPA-REAR-WHEEL-BRAKE-HUB-B49-M49-BULTACO-PARTS-BREAKING-BIKE/282849801825?hash=item41db297661:g:VRwAAOSwXOVadfjW

Wouldn't surprise me if the repro banana has nothing inside it.... I've just taken the banana off my 92 and replaced with a repacked but still with baffles clubfoot. Haven't tried it yet though

You might have to modify the inlet tube of the banana as they were made for the earlier engines with smaller diameter connecting pipes. It might be too small to mate properly with the 183 middle box outlet. Banana definitely noisier

There will be a very nice TX300 for sale at Telford Classic show at the weekend (not mine)

It's normal on most trials bikes to find them difficult to push in gear due to drag on the clutch. The drag is overcome better when it is the engine spinning the clutch, not the back wheel. But make sure the clutch plates are breaking evenly all around the basket as it won't help if they aren't. If not adjust the tension of whichever springs until the plates lift evenly The clutch pull is fairly heavy on the Ossa, you can experiment with backing the spring tension off to lighten the pull until it starts to slip. You can adjust the springs through the inspection cover, you don't have to remove the casing