Need some help ordering rings

[saturnthegiant]

I think i need to replace the rings in my '84 125m. It's smoking, and has some oil leaking out the exhaust. The other day i was riding in fairly high winds and couldn't get up much power. So i figured the best place to start was the rings. I looked them up on a couple of parts websites and they list two different sizes, .25 and .5. How do i know which to order? Do i have to take the head off and measure the cylinder and piston? It's my first time to tear into a topend. So, can somebody just point me in the right direction?

[dads]

first off you need to know if it can be re ringed, or if it has to be bored.
so off with the cylinder....

[gorbyback]

Yeah I agree with dads time to open the cylinder and find out how bad your cylinder walls are. Look for a local machine shop to bore out your cylinder, most of the time .25 should do it. Wait untill you get a positive answer on how much it will take to clean up the cylinder. When you buy .25 rings you will also have to buy a .25 piston for the rings also. A good place to check for a set of piston and rings is ebay. Just throwing in a set of new rings won't solve your oil issues untill there is some work done to that cylinder.

[dads]

If it needs to be bored get your piston first, and bring it with the cylinder tell them to bore no more then 3 mm over the size of the piston. that is min. bore.
max is 5, but at 5 your loss is 2 mm of cylinder you can wear.

[TimSr]

If it needs to be bored get your piston first, and bring it with the cylinder tell them to bore no more then 3 mm over the size of the piston. that is min. bore.
max is 5, but at 5 your loss is 2 mm of cylinder you can wear.


I think your missing a decimal point.:burnout:

[dads]

I think your missing a decimal point.:burnout:


your right your looking at .003