after putting a new timing chain on my ttr250 2004 model as it was stretched, and it has been starved of oil on the head due to the blanking bolt being left in (sounds nice running still)
I thought that maybe the excess heat on the valves and cams had killed the stem seals ( but it doesn't smoke much on startup if any) only at high revs and when being ridden it gives out a smoke cloud.
So I have assumed piston rings, I have stipped my cylinder and here are pictures.
I need help on the following;-
the bore looks ok no deep scoring but i wouldn't know if it was worn (I've tried my best to photograph this )
how do i tell it it wad rings causing this issue?
how do check piston rings?
how to a check exhaust cam chain guide for wear?
on my piston I cannot see any size, does this look like a genuine standard piston?
I plan on fitting new stem seals, piston rings and gaskets.
looking at your bore it is glazed it could do with glaze busting there looks like a bit of blowby past the two top rings i recon glaze bust bore new rings & stem seals will cure your problem
Standard bore is 73mm. It's a Yamaha piston, looking at the 4GY stamped in the top - highly likely it's the original. As Johnyboy says, your bore does look quite glazed, but a light hone would probably be enough. There ought to be a decent machine shop somewhere near you that would do the job for a reasonable sum. (My local guy in Redditch charges me a tenner and does it while I wait!) The piston itself looks ok.
You appear to be missing the top ring???
Provided it's still standard bore, standard rings will be ok.
All you can really check with the rings is that the ring gap is within limits. To measure this, carefully place the ring into the bore (not fitted to the piston!) Make sure it's level (same depth all the way round) and use feeler gauges to measure the gap between the ends. Acceptable limits can be found in the workshop manual, as can all the wear limit specifications (Sorry, haven't got it to hand or I'd give you the link) However, if the bore is glazed, no point fitting old rings. Start fresh.
Good luck,
Simon.
