woody

Probably no longer available as a new item anywhere (which would be new old stock as they're no longer reproduced) You'll probably have to look out for a used one Being a 1972 bike it will have the shaft with the fine splines if still the original shaft (ie: more splines, later bikes from '74 onwards had less splines, coarse splines) Shafts are the same apart from the number of splines, therefore interchangeable (same with the gear shaft, they come as fine or coarse spline) With the engine apart it might pay to swap these shafts for the coarse type as I think, not certain, that coarse spline gear levers and knuckles are more easily obtained than those for the fine spline shafts The kickstart shape on most Ossas is very similar apart from later Phantoms which are shorter but rare as hen's teeth anyway You mention buying the new knuckle to graft on a lever from another bike with left hand kickstart, some owners have done this as they don't like the long length of the Ossa lever

The tensioner helps smooth power delivery to the back wheel at slow speed in trials competition. For green laning you wouldn't notice not having a tensioner

Being an old style cast sleeved cylinder 50:1 is the leanest mix to use, modern bikes have plated bores so are fine on leaner mixes like 80:1 or 100:1 As someone else mentioned the spec sheet mix ratio is for mineral oils used at the time the bikes were manufactured. Just use any modern semi synthetic 2-stroke oil at 50:1. Castrol Power 1 is a decent brand that doesn't gum up rings or silencer packing

Your existing clutch cover also houses the adjuster for pushrod play against the actuator. If you put the later 1972 cover on there is no adjuster so you have no way of adjusting the clearance. The later clutches have the adjuster on the clutch pressure plate which is accessed via the large plastic screw in the later clutch cover so you'd also need to fit that along with a later type pressure plate and pushrod assembly Why do you want to do it, for appearance? Or better clutch action? If the latter you can get a light clutch operation with the original set up using Barnett friction plates which allows less tension on the clutch springs, therefore lighter pull. Also make sure the actuator worm drive is cleaned and greased and rotates freely, they easily get gunged up located where they are

Depends where you are. Keith Lynas or Alex Snoop in the US might still do them. No-one in the UK as far as I know In the UK only the MK1 MAR had the foil chassis sticker. From the MK2 MAR onwards and TR77 and Grippers, they all had the number stamped on the headstock, no sticker

There's a facebook group called hard to find twinshock trials and aircooled mono If you join that group they have a M80 parts manual in the files section you can download

There is an article on the BSA Otter site that shows how to widen the rear Cub/Bantam hub. The same front hub is fine for trials, skim to ensure it's round, get modern oversize linings fitted to the shoes and skim to fit hub I've no idea what AJS Archer hubs are but as for rules there is only one trial that will pull you up for hubs and that's the Pre65 Scottish. Most classic clubs won't bother which hubs you have, others have a specials class if they don't like your hubs

The forks could have been forced apart yes, but the travel would have been very stiff .The spacer could be wrong, in absence of knowing the correct length you could test the spacer length by fitting the bearings back in the wheel then push the spindle through the wheel with the speedo drive and spacer, if the spacer is too wide the drive shouldn't engage with the hub

I haven't got one to measure as I don't use a speedo drive, there is only one length so if it is the original item it will be correct length. If you have mudguard brackets fitted, try removing them as the brackets can pull the legs together enough for the forks to bind if they are tight, bending them outwards stops this

Not sure what you mean by using shims or washers, I just reduce the tension on the springs by backing off the screws until I get a pull that feels comfortable without the clutch slipping. I've also lengthened the arm on the ignition cover

I've never tried lighter clutch springs myself so I don't know for definite who sold them, they aren't an actual Ossa part, they're aftermarket. I think it may have been a company here in the UK called Rex Caunt Racing. They never listed them as a part in their product list so you'd have to contact them to see if they still stock them. With Barnett plates I just back the tension off on my springs to get where I want by trial and error

Possibly available from Spanish dealers but I'd be surpised if you can find one on sale. Easy enough to make or get made as it's just a tube with ID to give cleance to spindle diameter which is 12mm, OD and wall thickness to match the bearing inner race and the length is the distance between the two bearings. The two rings 105604 fit over the tube and are to help keep it near central in the hub and lined up with the bearings so that the spindle easily pushes through. Or the OD can be made larger to help keep it centralised and machined down either end to match the bearing inner race. All it does is stop the bearing inner races being pushed inwards when the spindle is tightened

The hubs on yours weren't chrome lined assuming the wheels are the originals, they are just normal liners, chrome came around 1972. If the chrome is in good condition the brakes work fine with modern shoe linings Easy to determine contact patch, just ride around with the brakes hard on and see the rub marks on the shoes. It's a lot less expensinve to get some oversize shoes and turn them down and try them before having hubs relined for no reason

Yes, based on the GasGas engine (which I think shared the rod kit with Bultaco) No relation to a Yamaha at all

When you say the shoes contact the drums fine, how much contact is there. Usually with EBC or Newfren etc you get minimal contact around the pivot but not much else. Oversize linings machined down to fit snugly in the hub give almost full contact and there are different materials to choose from. As above Villiers Services can reline old shoes to whatever thickness you want, as do Saftek

Have you got a replacement gear, 6 speed 199B gears are hard to find, In Motion might be able to help

Unless your hub is seriously worn and out of true, a better and cheaper option would be to have your old shoes fitted with modern linings which are oversize and then have them machined down to fit the hub. That way you get almost full contact of shoe to hub. Off the shelf shoes rarely give much of a contact patch as the lining is thin and only a small section of the shoe contacts the hub when the cam opens them. Modern linings also have more friction for better braking. Companies such as Villiers Services and Saftek offer shoe relining

The handy thing with the Falcons having no oil / gas separator is that you can drain and fill oil through the hole in the body with the valve removed. You can use air, you don't really need nitrogen on a trials shock, around 50-70psi with a mountain bike suspension pump. They'yy work better pressurised as it helps suspension preload and return

Modern 125 will easily have enough power for what you are going to be doing as a beginner regardless of your weight. I recently rode two modern 250cc bikes which were around 3 to 4 years old, GasGas and Sherco and they were both way over powered for what an average club rider needs, very sharp power delivery off idle - and the GasGas already had a flywheel weight fitted. The clutches were like jack hammers, designed to take up full revs launches, which made slipping them on tight turns a jerky affair, no gradual take up, they just bit. I've been riding for decades, it's the first time I've ridden a modern bike in a few years and those two were not suitable for most lower level club riders Regards rider weight, a 1980s 156cc Fantic could pull two riders and a sidecar, a modern 125 has a bit more power than the old Fantic

Gearing is personal really, or needs to suit what your riding entails, trials or just trail, playing about. For trials I find the standard 11:46 of the 520 chain a bit high as sections are a bit tighter than they were when these bikes were designed, I've used 11:48 on my M49 and others which means less clutch use in tighter sections. As mentioned above, 14/52 was the standard M49 gearing on 428 chain and other early bikes, but that is a bit higher than the 11/46 combination on a 520. Whether you use 428 or 520 won't make any difference to the bike but you might find there are more options with 520 rear sprocket sizes although there is only an 11 tooth option for the front

The easiest way to get the engine out of the frame is to first remove the cylinder and head with engine in the bike, then remove the engine. It is possible to remove the engine with cylinder and head fitted but it can be a real struggle, much easier without - same when refitting. Also easier with the ignition and clutch side casings removed. To remove the cylinder and head you'll need to remove the middle silencer as the head will catch the front of it. For the engine, remove the two rear and one of the front engine mount bolts, hold the engine by the cylinder studs and then remove the last front bolt, the engine will drop forwards and out or lift out For engine removal the only proper tool you need is a C spanner that correctly fits the threaded ring that holds the exhaust in the cylinder. If you try and undo this using a hammer and drift to unscrew it you risk damaging the threads which are fine - also be careful when refitting as it's easy to croass thread it when it first goes in, it should be easy to make the first few turns by hand, if not, it's probably crossed. To remover the rear engine bolt a knuckle joint on a socket extension is useful as it's awkward to get at. The only other tool needed is if you are stripping the engine and that's to remove the rapered sleeve for the clutch cush drive and a puller for the ignition flywheel but if Steve is doing the engine you won't need to bother with that

It's just what some people do, the oversize 82mm piston gives about 340cc so someone has made a 350 decal for it. Some do it for the TY250 Yamaha when an oversize 70mm piston is fitted, they have a 270 decal made for it

Someone has just made a 350 sticker up. They were 322cc badged as an RL325, 82mm is an oversize piston

It was the clutch end I was referring to but I got the sizes wrong as I was trying to remember from some bearing sizes I'd scribbled down ages ago, I think I've given the bearing widths. The shaft for the clutch hub on the M80 is 15mm, the larger shaft is 17mm. I thought that was introduced later than '72 but It's years since I rebuilt my model 92 which is an early number from '72 so I forget what's in it so possibly yes, 17mm came immediately with the 91/92 models The Alpina came in 1971 so possibly early numbers had the smaller shaft, I don't know but something to check before buying a Sherpa gearbox

I'm not overly familiar with Alpinas having never owned one, but I think the earlier M97-99 range of frames are more akin to the series 1 M91/92 Sherpa frames, hence the rear facing tensioner and recessed swingarm spindle For a gearbox swap you need to check which mainshaft your M85 engine has, M80 and earlier Sherpas had 13mm diameter where it extends into the clutch with the clutch hub held on a woodruff key. Around 1973/74 the mainshaft was enlarged to 14mm with a splined end and had a larger bearing to take it. The clutch hub was now larger and also splined for the larger mainshaft. This also required a larger ID for the top hat bush behind the hub. As the M85 Alpina ran from 71-74 later number engines could have the larger mainshaft box, I don't know for a fact but just a possibility bearing in mind they went through about three different frame designs, you just need to know which you have as early and later type shafts aren't compatible