feetupfun

Yes removal of the primary gear from its taper is a special challenge, and the sprocket on a 348 is also on a taper and is usually very hard to get off. The cylinder nuts are also an unusual size (7mm internal hex), and usually bound to the studs with corrosion so for your first two-stroke crankcase split, you have got a bike with extra challenges compared with the majority of bikes. I suggest that if you are only splitting the cases to get the case welded where the kickstart makes a hole, then plugging the hole some other way is a practical alternative. The hole in my case was sealed with silicon rubber about 12 years ago and has not been a problem in any way since then. I have another case ready to go that has been welded up to repair the hole, but nothing has gone wrong with the motor in that time so it remains a spare.

check power is getting to fan, if yes check fan motor on a battery (12VDC) if no power getting to fan, check fan switch and power supply from rectifier

Some actions (usually within a turn) in mototrials can really load up the steering. Straight ahead is usually not an issue. The ideal width is usually the widest that still allows the rider to use full steering angle in all positions.

The sparkplug appearance shows the combustion conditions at the time that the motor stopped firing. If you want to read the sparkplug to check on the mixture at full throttle, you have to stop the engine while it is running on the main jet. Just because the fan starts and stops normally, that is no reason to think that the motor is jetted correctly throughout the range of throttle positions. The fan responds to coolant temperature, which lags changes in the heat production rate. The thermal inertia of the cylinder and coolant is the cause of the lag. If the lean mixture only cause brief periods of increased heat production, then fan operation will appear normal.

Yes if you fill the coolant system to the brim it will eject some coolant out through the overpressure valve as the coolant expands with temperature rise. I'm only guessing here but maybe for some reason your motor is getting hotter than normal when you wheelie, but you haven't given any details of what sort of wheelies you are talking about so it makes remote diagnosis difficult. One thought I had was that maybe your radiator fan runs backwards, and the only time your bike is ridden fast is during a wheelie, so there might be little airflow through the radiator if the fan starts while you are going fast? (fan working against the natural airflow ditection when the bike is moving fast) Same for "big climbs" are you talking 10 minutes or 10 seconds of continuous climbing? Fuel coming out the overflow usually means either a passing float needle valve, or the fuel level set too high in the float bowl. If it only comes out when you are riding, the level is set too high, or the overflow standpipe has a problem. If it comes out when the bike is completely stationary ie motor stopped and bike upright and sitting on a stand, it is a passing float needle valve. If you can leave the bike parked with the fuel tap on, and there is still fuel in the tank (and not on the floor or in the crankcase) when you come back to it, the float needle valve is working fine.

with the carby upside down and the gasket in place, measure from the upper surface of the gasket to the top of the floats

Looks like Pursang to me

Yes I think the seller is serious but misguided

Your red oil is travelling along the clutch pushrod from the primary drive case and coming out where the pushrod exits the hole through the gearbox output shaft.

The nut will not be a problem, but I suggest to bring a 100mm angle grinder home too so you can cut the sprocket to get it off its taper

It may also be the finish on the rechrome not being completely smooth yet (requires running-in of the surfaces by riding the bike).

What a question! It depends on how much you believe of the description and if you need to buy a proper front end to fit to it (maybe you have a TY front end already) The description sounds dodgy to me because the seller is claiming it has a new fuel tank (unlikely), and did not mention those completely unsuitable forks.

It could be somesthings wrong with the bike, or could also be that you are not used to riding 1970s bikes. You would know if you tried a similar bike that was known to be in good condition, or if you got someone who knows OSSAs to ride that one you looked at.

If you think you will make money fixing up something like that you are dreaming. Only buy it if you actually want it for yourself

bash plate airbox hose side cover chain rechrome forks chain guard trials handlebars

I did not seek to criticise. The questioner is actually a riding buddy of mine. I helped him with his question as far as I could a month or so ago, as did many other Bultaco lovers in his acquaintance, but this was not enough to answer his question, so I suggested that he pose the question on this forum in the hope that someone else could help. When I saw that the only reply posting (yours) appeared to claim to provide the answer, but the listing that the link opened only contained brochure photos typical of M199 and M199A, I was concerned that people who may have been able to help, may not open your link, and possibly assume that your reply had answered his query. The outcome for my riding buddy has been some helpful replies. Thankyou everyone who has contributed so far

So you haven't worked out who he is yet? I'll give you a clue - he rode at the same Twinshock Masters as you and I but didn't ride the bike in question

I looked for many years for a 198 or 198A and in that time was offered countless 199s and 199As. I eventually found a 198 (thanks Reginald) which is in the process of being readied for use. I totally agree about the virtues of the 250 motor compared with the 325, for people who want an enjoyable ride.

I reckon about the same helpfulness but yours is also humorous so it gets extra points

That list shows a silver-framed M199 and a blue-framed M199A but does not answer NedKelly's question

About an inch less than the ones on my M49. You can measure them in the time-honoured Reginald way if you want. There is a new set not fitted to anything yet.

Have you compared it with another similar bike? Is it the same frequency as the engine rotation? Did it start suddenly? Is it there hot and cold? It is normal to be able to hear the piston rocking in a four stroke at some RPMs if the exhaust is quiet enough. Also possible to be noise from the valve train. Knock knock at engine speed - piston noise. Tap tap at engine speed - valve train noise. Ticking or clicking noise that happens irregularly may be cam chain noise

I just measured a couple of sets of Fred and Deb KT bars at 835mm

A man with an eye for detail

If someone has cold virus it is considered good etiquette to wear a particulate filter mask to avoid infecting other people