feetupfun

it is the first four digits of the numbers that are relevant. It will probably be something like 493-2****** or 493-1********

If you are still having problems identifying the motor, post some photos showing the engine covers, cylinder and head

you could take the cylinder head off and measure the diameter of the bore. TY175 standard bore is 66mm diameter If you have a clever way of measuring, you could alternatively either take off the exhaust pipe or the reed cage and measure the bore The TY175 and TY125 have the same stroke Lots of TY125s have been made into 175s over the years

From memory, it's the pressed aluminium cover that has the OSSA film reel symbol and is held on with two screws. Located on the side of the clutch cover.

Those numbers give 50 pounds per inch

If you want it identified, post up a decent picture of it and have a look at the frame and engine numbers to see what they start with. Yes they sold twinshock TY250s until the late 1970s. The design did not advance since the 1976 model, but there a few changes of graphics after that and different-looking models were sold in different places around the world Before you start it, remove the powdered remains of the foam air filter and fit a new one before that stuff gets sucked into the motor. Clean out the carby especially the pilot airways and pilot jet Clean out the fuel tank and fuel tap Check for spark Motors sitting a long time without a good protective coating of oil on the crank and conrod bearings often suffer catastrophic bearing failure when put back into use. To avoid unnecessary damage to the cylinder piston and rings, consequent to a bearing failure, be ready to shut it down fast if it starts making odd noises.

Some 348 forks had soft springs that needed air assistance and some 348 forks had normal stiffness springs. Be aware that the springs in your forks may be either type so your forks may not need air assistance. I have both types of springs to choose from for my 348 and have found that normal stiffness springs and no air assistance provides a better action, most likely to having less friction at the seal lips.

Have you tidied up the bore of the tubes? I had a set of seized 348 forks caused by being full of water for a long time, and I had to linish/hone the surface of the bores to get the pistons to fit and work nicely

I tried B&J Racing springs in TY250 twinshock forks and found them to be too stiff in the initial part of the travel. I don't know anything about the twinshockshop yokes

I find that 50 pound springs on Falcons gives a fantastic action. I suspect that Betors have a bit too much compression damping which makes them ride a bit harshly when combined with springs that are on the stiff side.

if you can measure the wire diameter, the coil OD and count the number of free coils, the rate can be calculated. Post the numbers here and I will do it I would say that John Cane sells springs for trials Betors

maybe you have Alpina/Matador gear ratios and/or primary drive sprockets inside your M92 motor. If you want to test for this, you can work out the gearbox and primary drive ratios by counting how many turns the motor does for one rotation of the gearbox output sprocket in first gear and compare that to the specs for a M92

The standard gearing on 1970s bikes is much higher than on mono bikes. It was chosen to suit the sections being ridden at the time. Your M92 is best suited to a smooth continuous flowing riding style which can seem quite strange to people used to stop/start riding. If you practice enough using 1970s technique, you will get used to riding it. If you gear it down to make it like a later model bike, it will be too slow in first gear for big jump-ups. The ideal setup is to have the motor running turbine-smooth especially on closed throttle and the transition from closed throttle, and never use the clutch. Idle set so the motor stops when the throttle is closed in neutral.

OK I see there are no triple clamps included with those 348 forks so 35mm triple clamps from some other trials bike with leading axle forks would be needed The most common fork swap for heavier riders on TY175s is to fit TY250 twinshock forks. They are 34mm diameter and the TY250 twinshock front end is interchangeable with no fuss with the TY175. One of my TY175s is set up like this and they work well - I weigh 95kg.

OK - like Italy, we (Australia) got 348s with fibreglass tanks so are very familiar with them. The steel insert for the cap is standard in the 348 fibreglass tank. I'm pretty sure you have the same fibreglass tank as what he have here, so if you want to have a look at the fibreglass, take the tank out in the sun with the cap off and let direct sunlight fall on the tank. If the cap tube limits things too much, find a bright light source and put it inside the tank while the tank is somewhere dark. If it has never been relined or repainted, you should be able to see the light coming through the walls of the tank, and that will show the pattern of the glass within the matrix. For info, here is a photo I took recently of the inside of a 1974 Sherpa T tank, before I relined it. The photo uses just the flash from the phone/camera. I don't have any photos showing the way the light penetrates the walls.

Do you mean Marzocchi forks or Cota 349 forks? If you mean 349 forks, I think I have measured them up previously and found they are a bit short - so the front of the bike would end up lower. You could probably find longer tubes though. The leading axle design of the 349 forks would require you to use the Cota 349 triple clamps to maintain suitable steering trail on the TY175. For heavier riders, the 349 forks would have a better action and spring rate than the TY175 forks.

Why are you not sure what the 1977 tank is made of? Can't you see inside? What do you mean "from Italy"? If it was made in 1977 it was almost certainly made in Spain and definitely made of fibreglass. Try and work out why the 248 tank is so heavy - it may have been lined and/or repaired, and if it has been relined it is very important to know what it was relined with if you are thinking about relining it again I would recommend getting the aluminium tank fixed and use it in preference to a fibreglass tank

Welcome tworivers It would help knowing what parts you need and where you live Also there is a wealth of this sort of information already in the Yamaha forum

Just thought of something else. If you are burning gearbox oil via a seal leak, the colour of the smoke is usually a lot whiter than the smoke caused by excess premix oil, or the burning out of gunk in the exhaust, which usually is pale blue

I also think it might be the clutch side crank seal, and if it is, the reason why it may still run and idle OK with that problem is that while it is sucking oil through the seal, it is not sucking air. I also suggest you check the oil level in the gearbox before riding it, to avoid the risk of damaging the gearbox. Also, worn rings don't cause exhaust smoke on a 2 stroke.

Here is what it ended up looking like

I'm just theorising here but if they had been stuck for a while, maybe they didn't seal too well to start with then improved as they bedded in When I have had them unstick, it has been the result of getting the motor much hotter than normal for a brief period, and I noticed the improvement in performance pretty much as soon as the motor was back to normal temperature, and so was able to identify the cause of the performance improvement

stuck rings can free up with use

the fan is not unique to the Beta so seek alternate (economical) supply source - and is probably 12-24V DC. Definitely same fan as many other motorbikes and may also be the same as inside desktop PCs. Fan motor failure and thermostat (switch) failure are relatively common issues. I imagine that the fan motor cops a hiding if the fan blades get fouled up with something.