feetupfun

Wiggle the clutch arm while you are trying to turn the clutch arm adjusting screw anti-clockwise. There may be a burr on the peg on the adjusting screw that is catching. If you are in doubt about what I'm saying, have a look at a parts diagram and you should be able to see how it works

Sounds very odd. That key shouldn't see any force if the taper is holding properly

You unscrew the clutch arm adjusting screw which is located in front of the sprocket

If there is not enough air space when you put the cap on, the pressure relief device will let out some coolant as the coolant heats up and expands. As it cools, the vacuum relief device will let some air in. If you leave it at that, you shouldn't lose any more coolant

Yes it's OK, it should have clearance the whole way along. It stops flowing fuel when the venturi effect stops which is when the slide gets to the bottom

beside the hinge for the oil tank

I still use my local auto trimmer/upholsterer

Yes the late TY250 is different to the TY175 and both are different to the early TY250 seat

Flywheel effect is definitely a personal taste thing. I suggest you try riding it however it is now before making changes. It can be a pain trying to refit the steel band to a TY250 flywheel. TY250 twinshocks have become fairly popular around here over the past 10 years so I've kept a flywheel with no band that I lend to people so they can try it on their bike before they do something to theirs that's hard to reverse. I machine about 1/3 of the steel band away on my late model TY250 flywheels and have left my A model flywheel with the small band standard.

The wikipedia story reminded me of yet another variation from an early Cat Stevens song that includes "pumpin' petrol gas"

I have always wondered where the "gas" name for US car fuel came from, but there is nothing strange about how they identify gas. Gases are identified by name, same as everywhere else.

The pressure relief valve may be blocked and that could be the weakest hose connection

I'm pretty sure those studs are cast in place

Photos would be much more useful for identification

Sorry I don't know what you are trying to remove but I'm sure you can also make use of gravity to help prevent particles entering the intake or exhaust port. On one of my bikes (an OSSA) I always string the bike up upside down when I take the cylinder off so that no rust or dirt falls into the crankcase.

Do you have the important dimensions JC? George is a master at sourcing pistons for oddball motors

There are plenty of coatings available to protect stored metal. They are usually waxy and work by not allowing water or oxygen to penetrate and can be removed with common solvents. Available at bearing, tool and machinery shops

The piston numbers say that the piston is 0.5mm oversize (0.5mm bigger than standard). From what you have said, you should have the cylinder rebored to a larger oversize. Which oversize to use can be determined by measurement of the cylinder by someone experienced at the job (usually the person who would be doing the rebore work) Some brands of pistons are available in size steps of 0.25mm and some brands are available in steps of 0.5mm. The biggest piston kit available is 2.00mm oversize. Unless your cylinder is extremely worn, you are likely to only need to increase the piston size to 1.00mm oversize. Don't buy a piston kit until you have had the cylinder measured.

The tank decals, being so crooked, give me doubts about the quality of the rest of the resto

I find that if I let the fuel in the float bowl evaporate (which doesn't take long here), the next time I ride, the pilot circuit misbehaves for the first few minutes. The fuel in the tank seems fine though for at least a month. I'm not game to leave the fuel tap turned on to prevent the bowl drying out, so to avoid the problem I usually run the float bowl out of fuel before parking the bike if it's going to be a couple of weeks to the next ride. I think if it was a colder place it might take longer for the fuel to evaporate from the float bowl. I imagine that a heated storage in Canada would also evaporate the fuel in the float bowl in a couple of weeks. I expect it would take many months for fuel to start turning to goo (polymerising) in the tank, but its combustion properties will begin to deteriorate as soon as you put it in a vented container (the fuel tank) due to evaporation of the lighter components.

I made the mistake of having only diesel cars and we are in a drought so the lawnmower doesn't use enough to get rid of the old premix so I give it to a friend who has a petrol car. We have great petrol here in Australia compared to the horror stories I hear from the USA and the UK, but I still avoid using anything over a month old in my trials bikes. You will soon find out if the fuel is too old or not when you go for a ride. I value my riding time highly enough that I don't want to risk having any bike problems when I'm out for a ride. For the relatively low cost of using fresh fuel, it's an easy decision. Good petrol here is about $AU1.50 per litre

same here

That gusset in front of the rear upright must be pretty close to the rear end of the main chamber of the exhaust

When I bought Boyesen reeds for TY175s and TY250s in the 2000s, the instructions said to fit them without the Yamaha limit plates. Are you saying that at some point in time, the limit plates were intended to be retained when you fitted Boyesen reeds?

Flywheel may have moved on crankshaft, putting timing out