sounds like the running at high revs without a good warmup damaged the motor.

from here, I'd be considering a complete overhaul.

Who the hell put a cardboard cylinder gasket on it ?? The actual head gasket ??

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

Gofora strip down and replace the cam chain,check the head and do the valve seals and rebore/hone the barrel and new piston rings and all will be good.....and use original yam gaskets,I did,nt and bought a kit off flea bay only to end up buying yam ones....

I wish I was joking - I shoulda mentioned this is on-the-road repairs in Africa. I was watching them do it and asking: "Are you sure?" to which I got: "Yeah, sure, no problem!" This is my first bike so my motorbike mechnical knowledge comes from the 6 months that I've owned it so although I'm learning, if a "mechanic" says that's the way it's done then that's the way it's done.... until I find out that's NOT the way it's done!
Today we (me and a real mechanic) took the bike apart - put the piston in the cylinder and it dropped like a rock. Cam chain is also def no good. Got a real Yamaha piston and tommorrow (from what I can gather with my limited French and mechanical knowledge) we'll be putting that in and doing something to the cylinder (a rebore? is that what you call it?).

So, no smoke at all at start-up, only when it's running a bit. I changed the crank and rod in Niger - this guy had them but absolutely no other part for the bike, I've no idea where he pulled it from. Chain and piston to be replaced tomorrow - what should I be looking at on the tensioner?

What does a complete overhaul entail besides the aforementioned?


And finally.... You think the high revs when not warmed up caused these probs or it's just bad luck them all coming around the same time? Do I need to be keeping my eye on anything else? Thanks all....

edit: forgot to mention the top of the piston and the valves were caked in burnt black shit, not sure how old it is though. (don't think it's that old)

A loose piston and a streched camchain shouldn't come from beating the bike when cold as I see it.

general flogging of a bike can cause wear like that. but I'd expect if you're running low quality oil, that has a bigger impact