dt 125 R piston ring Q's

[dtdynamics]

heya all first post here thinks its a great site loadsa info!

i was wondering i have a yamaha dt 125 R the year is 2002 and i have blow by past both rings down to about half the piston. rebuild done about 2 months ago or approx 1500miles since. cylinder has totall of around 17000 miles on it. i think the rings are to small for the cylinder,

so the question is:
1.will oversized rings fix the problem and can they go straigt onto the orignal size piston
2. if not will the cylinder have to be rebored/honed to fit the new oversized rings and piston

also is there an effective way to measure the cylinder bore if ya have no bore guage?

thanks lads!

[dtdynamics]

any ideas lads?

[Rotorranch]

With 17,000 miles, I'd say you should have it bored, and an oversize piston fitted.

A good motorcycle shop will be able to measure the bore, and determine which oversize piston you will need. I'd try to use the smallest oversize piston you can, to facilitate future rebuilds.

This is assuming the cylinder has a steel bore.

Rotor