I bought my ty250 mono six months ago and have just got round to using it but have discoved it has a rattle on the engine so a mechanic had a look as it sounds like the piston is hitting the head.But the piston shows no sign of that there is no play in the big are small bearings just a bit of wear and tear so he put on a exta base gasket but it still clunks and rattle . So i wonded if any one has any idears on what it could be also what oil do you put in the gear box ? Thanks

First step i'd post this in the yamaha section. All ty mono's seem to tap a bit, there's even the urban legend of a guy who got a full rebuild done on his engine and it still tapped!

It wont be hitting the cylinder head or spark plug, you'd certainly know if that happened.

Search the yamaha section and you should find more info about tapping.

It might be some piston rings might help, or a rebore or even just some octane booster in your fuel which i found helped mine.

Thanks for the reply im going to try the octaine boost as i think that mine is just pinking so fingers crossed.