woody

As mentioned above the frame number is a DIY stamping, not Bultaco, The number isn't even formatted correctly as there should be no 'J', that prefix was introduced around 1975, it should just be a B prefix. It would need to have a frame number related to its age to get a dating certificate to register it on an age related plate, that's probably why it has been stamped up like it is. If you take the paint off the other side of the headstock you might find a trace of the orginal number unless it's been completely ground away Engine stamp is genuine

The frame isn't a model 27 frame, it's from a later model, looks like a model 80, could be a late model 49 or even an Alpina. The number on the headstock would normally identify it but if that is a prefix 27 number it has been restamped. The M27 frame didn't have a mesh guard between two frame tubes, it had the Y shape frame under the engine with a bolt on sump guard To restore to an original M27 spec is going to be an awful lot of work and first you need a frame. Also a tank, seat, airbox, sidepanels. It's going to cost a lot. Personally I wouldn't bother, you have the basis of a useable bike which you could use and enjoy for what it was intended - throwing up sections. Does it matter if it is a non matching frame/engine, it won't cost you marks in sections... You could make it look like a model 80 slimline for a lot less than trying to restore to M27 looks. I'd guess Motofibre could restore the tank side piece where it's been cut off for the exhaust. Recover the seat, get the exhauist altered to the correct angle and you're nearly there. In terms of engine performance there is little if any difference between the M27 through to M80 range The upgrade you mention was made available to convert the model after the M27. the M49, to M80 spec

1. 50:1 with modern oil - Castrol Power 1 is a decent oil and very clean burning 2. 1 litre capacity as clutch and gearbox share the same oil. If you're changing the oil probably 900cc as there will be some left in after draining, but there is a level plug bottom left of the clutch cover 3. No points, ignition is electronic on the MAR. The 1977 - 79 TR77 (green tank bike) have points, they aren't strictly a MAR but are still called by that name. However, as the bikes are over 40 years old it may not have the original ignition as they are interchangeable. Can't help with gaps but I use BP7ES NGK, I think recommended is an 8 4. CR is about 10 but it may have that info in a manual The frame and engine number will tell you which bike you have, they would have matched from the factory but again, in 40 years some bikes will have had engine swaps. Frame number is on the headstock, engine number by right side front engine mount, If you have an early MAR the frame number was on a sticker so may no longer be there. You can download a manual here https://www.custgp.com/a1manual2/Ossa 250.pdf A lot of info here http://www.vitalemaquinas.com/

Prefix 43 is a '75 310cc MAR. There are a couple of chassis prefixes that are missing from the ID charts for some reason Fingers crossed your engine is in good order as the 310 cranks can crack around the pin and are like rocking horse teeth and 310 pistons are also very hard to find

Sent you a reply to your facebook post but this is it pasted below The serial number begining 70 is a TR77 Verde 250cc. That serial number doesn't appear on any of the ID charts. The top shock mounts have been moved down but not by much, up to one inch maybe as originally they were just below the top sidepanel screw. I'm not sure what the grinding would be at the top of the tube as there was nothing there on that side on a Verde The forks and yokes are from a MAR, the forks are MK2 MAR. They are shorter than the TR77 forks by about 2 inches. Most riders raised the forks in the yokes on the TR77 by roughly the same amount to reduce the chopper effect of the longer forks, so using earlier MAR forks serves the same purpose. The rest of the bike looks to be as it should The pinch bolts and bar clamp bolts are 7mm thread on those yokes. I think the rear shock mounts are 7mm on the TR77 also Front wheel is from an ealrier model, probably MK2 MAR as well, as the Verde had a gold rim although the wheels are the same on both apart from rim colour

The frame number and engine number would have matched when the bike was produced so if you can't find a frame number on the headstock check the engine number against this chart which will tell you what you have. The only difference in the numbers is that the frame is prefixed B and the engine prefixed M http://ossa.2y.net/ossa/bilder/modelos/index.html

My first bike was a Challenger - it's a pure scrambles bike, totally useless as a trials bike, the engine characteristics are for speed with no low down torque

I don't know what you want or why Spud. You only use your bike a couple of times a year at trials local to you, so unless you travel around the country either riding or spectating at numerous Pre65 events, when are you going to see the standard bikes that you want to see back in circulation? If you want change you're going to have to convince the clubs that run these events in your area by getting the support of other riders who feel the same way - have them lobby the clubs with you, find someone who knows the old bikes in detail and see if they will scrutineer at each event. I imagine you won't... The decline of these bikes is due to the riders that used to ride them getting ever older and no longer able to handle them, not rules. Our local British bike club had several riders 10 years ago on big bikes as they enjoyed riding them. They are all riding lightweight Bantams now, nothing to do with rules, cheat bikes or anything else, purely because they can no longer manage the big bikes. Excepting your area, there are still trials that accomodate these bikes and the riders who enjoy using them do just that - they don't care what anyone else is riding, they are getting their day's enjoyment riding their own bikes. As I said before, you're trying to fix something that isn't broken

@Spud you only ride once or twice a year yet you're advocating all trials include a class for standard bikes and provide a scrutineer to check that they aren't fitted with ineligbile parts... So you've no actual experience of other trials throughout the country, the views oif riders who compete in those trials or whether they perceive a problem or not. If you only ride that little where do yo get the idea there is a problem that people don't want to ride standard bikes because there is no class for them - who are you speaking to? As I mentioned, it's more an issue of age as I've seen first hand riders over the last 10 years or so move to modified lightweights in order to keep riding. It's as simple as that. One of our local clubs has recently begun to enforce a rule that hubs and yokes can't be anything other than British. All this has done is reduce their entry as riders with bikes that don't comply no longer ride there... As for scrutineering for a standard class, who do you think wants that job? Who is even has the knowledge now to assess a bike from the 50s or early 60s? Those people are now in their 80s. Clubs have enough on their plate organising trials, especially road trials where numerous people have to be contacted for permission to use land, not only for sections but for access and rights of way as well. Then there is the setting out of sections at multiple venues, clearing undergrowth from land only used once a year, marking the route, removal of markers after the event, results, paperwork. The number of people willing to do this is diminishing but of those that still do, their age is increasing, not many are coming through to take over. An additional issue of whether a bike has the right magneto or fork internals is not something they are going to embrace - especially when there is no perceived problem from riders actually participating in their events You're trying to fix something that isn't broken

Of course it's about excluding if you maintain that you can't cater for both. If you're not willing to do something about a problem that you perceive, why keep dragging the subject up? Cheating implies that someone is hiding or not disclosing something and stating that something is what it isn't. Pre65 is just a class name. There is no cheating going on, everyone knows what the bikes are and no-one is hiding anything or cheating so I don't know where you get your ideas from. 30 riders at the NBBC... were you there to count them? If you were I hope your job doesn't entail working with figures.... Try around 70 for the last few rounds and around 120 for the first.Not bad seeing as some people still haven't started back due to covid worries Yes there were big bikes in original spec which are those I referred to as having cleaned a section that some riders on modified lightweights didn't. Pre65 orginated in the 70s which gave riders who were no longer competitive on current bikes the oportunity to drag old British bikes out of sheds and have some fun - nothing to do with cost. These riders would have been around their 30s then so most would be well into their 70s now. How many do you think are still capable of riding those big, heavy standard bikes. That is also a huge factor in what you see as a decline in big bikes being entered. Few riders from subsequent eras have any interest in riding those bikes. Older riders have been able to continue ridng into their 70s and even 80s purely because of the modernised lightweight Cubs and Bantams. Without them they would have hung up their boots long ago and it's likely there would be virtually no British bike events without them - what do you think the average age at one of these events is? Try going to some events. speaking with some of them and get their views on the viability of them riding an original spec British bike

So in the 5 years or so since you last raised this topic what have you done? Again you're calling for class changes, rule changes etc to existing trials which are well supported and don't need them. Why? In those 5 years you could have drawn up a set of rules and regulations for a genuine Pre65 British Bike series within the guidelines you mention and in which you can exclude all of the modernised bikes by having a dedicated scrutineer at each event. You could have lobbied clubs in your region or wider afield to find any willing to help you stage events for a pilot series, got your ideas out to riders, clubs, organiusers using facebook which is now the prime media for promoting events and see what level of support you would have. Run a pilot event to your spec and see what level of support you get. Why insist everyone else change whatever format they have when that format works and riders are happy with it. If you want trials for original bikes only you have had a long time to get something up and running With regard to actual events, I was at yesterday's NBBC round at which there was a variety of bikes in different states of modification from stanfard big banger rigids and pre-units to the latest modified Bantams, Cubs etc. A section I was helping observe on after my own bike had a mechanical, had a tricky exit but saw cleans on the easy route from a couple of rigids and pre-units whilst many riders on modernised lightweights lost marks - yet you say the two don't mix... I think before you comment about how rules need changing you should attend some of these events and ask the riders themselves - from the feedback, everyone had an enoyable day at yesterday's NBBC round

That's good news, I saw a facebook post a few days ago with only around 30 entered it was in danger of being cancelled, so good to see the entries have picked up. It's a very enjoyable trial

I don't thnk there is one for the TR77 specifically but there is an engine build manual for earlier 5 speed models which will suffice for the TR77 as they are pretty much identical http://ossa.2y.net/index.html Also parts lists here and other useful stuff for most Ossas http://www.vitalemaquinas.com/descargas.htm

Yes they are

The best option is buy the green mudguards and then match the paint to them. The current green guards aren't the same shade as the originals which were darker and a bit drab. I don't know the RAL code for the original green, also a bit drab looking, and doubt anyone has it but if you did manage to find it and use it for the frame, the mudguards will be lighter and won't match The black was usually semi gloss / satin rather than full gloss

The gearbox from an M85 Alpina should go straight in but later models will have differences in shaft diameter and clutch hub mounting so aren't a straight swap Much easier to just change the sprockets than gearbox ratios. Standard Sherpa size for that year is 11 / 46 for a 520 chain or 13 / 52 for a 428 chain, just fit bigger front, smaller rear

34 is a MK1 Ossa MAR 1972/73 250cc. The frames weren't stamped with a number on the MK1 they had a sticker on the headstock. The frame has been repainted as they were siver/grey originally

Autotek is acrylic paint and may not be resistant to petrol - most modern paints don't seem to be. If you spill any whilst filling the tank you could end up with an unsightly blemish if it isn't. Paint something else that doesn't matter and when cured pour / rub some petrol on it, better to find out that way than ruin you tank paint job. Halfords paint for example is acrylic and although gives a really nice finish from a can, when it comes into contact with petrol it virtually dissolves

The 199 exhaust has a higher rise over the head than the 191 pipe so it will sit a lot closer to the underside of the tank. It also bolts directly to the cylinder so you'd need to remove the manifold from the 191 cylinder. You might also find the outlet doesn't match the inlet of the rear silencer in respect of tube diameters but if so that can be sorted by welding the correct size tube to either one. You're not really going to know the answer to your question completely without trying it For interchanging parts it's difficult to give a precise answer as there are differences. Not many engine parts are directly compatible, head and barrel can be changed together but not individually as 199 uses a head gasket, 191 doesn't. Gearbox internals are different, crank probably looks the same but the 191 has a single bearing on the clutch side, the 199 might be a double, can't remember. Forks and wheels are the same

They shouldn't leak. I've found using talc helps pinpoint where it first comes from, dry it all off, shower it in talc and then you can see where the wet patch first appears What can happen with the MAR is that the bashplate gets bent upwards in the middle from repeated contact with the scenery and this can expose the sump plug. If the plug then starts taking hits it can crack the casing around the plug but yours looks fine. It could possibly cause distortion which stops the cases mating fully, not sure Some of the gaskets these days are horribly thin and if there is any imperfection in the mating surfaces oil finds a way past and drips Yours has grey sealer as well as a gasket., possibly 3 bond as that is grey but that would usually fill any imperfection in the mating surface I'd have thought as it's good stuff The gear shaft has an O ring either end but from the ignition side it can't be replaced without splitting the engine as the shaft can't be removed without splitting. It might be possible with the end of the gear shaft cut off flush with the casing to expose the O ring if the shaft is pushed fully inwards with the clutch cover off I've found with these older engines that it's best to put a little oil in before fitting back into the bike and leaving for a day or two to see if there are any leaks. A short term fix is dry it all off once you've pinpointed the leak and apply some plastic padding leak fix along the gasket which should hold it. The only correct fix is a strip and inspection of the mating surfaces which might need facing off or to see if there is a hairline crack anywhere First though, see if you can tighten the crankcase screws any further - you never know...

If you leave it as it is it can't the bolt should still secure it as it is also held with the straps below the seat - but to repair it I'd fill with fibreglass resin and make solid again, then re-drill the holes

As mentioned the tank cover holds it on, bolted at the front and straps at the rear below the seat

I think wherever you buy the points from they are going to be the same pattern points you have already got. Ideally you need to try and find a set of original Femsa if they are still available but no idea where you would get some from. All of the parts stockists I know of, Spain included, sell the pattern points. The issue I had with them is the position of the terminal screw for the wiring which sits directly in front of the coil and makes it extremely difficult to connect the wires - enough so that I bought electronic for my bikes. Add to that I absolutely hate the fiddle of trying to work through a stupidly tiny hole in a flywheel...

It's a cover from an earlier 349, the MK3 white model '81, not an '84, the last MK4 349 from 82-84 had a plastic tank, also with flat sides, no molding behind where the round Montesa badge fits. But yes, someone has just cut it to slip over the bolt

You can only use road legal enduro tyres on the road - they are marked with the E mark in a circle. If they don't have that they aren't legal for road use. You won't need an MOT to register it on a 74 plate, nor insurance.