250SX Top End Rebuild

[Yamaha Tri-Moto]

Just curious how involved it is to replace the rings on a 250sx?

I want to take apart as little as possible. if I just want to change the rings and I buy a top end gasket kit and set of rings will that be all I need?

I'm assuming I need to take the head off as well to get to the piston.

What's the simplest way to do this. First time doing a 4 stroke.

[350for350]

It sounds like you're on the right track. I hope you realize that you will have to take the engine off of the frame in order to do a top end. Why are you just replacing the rings? Do you know that the piston is in good shape? How about the cylinder bore?

[Yamaha Tri-Moto]

Oh really, I guess I'll scrap that idea for now. Compression is still 150 so I can live with that for now I guess. Thanks

[shortline10]

The Cylinder head comes off without removing the motor , it’s a little tight but definitely doable , I have rebuilt hundreds of these over the years .

[Yamaha Tri-Moto]

The Cylinder head comes off without removing the motor , it’s a little tight but definitely doable , I have rebuilt hundreds of these over the years .

So I would have to take the head off, then the cylinder and the motor could stay in?

Would I only need the top end gasket kit and rings to do the job?

[patriot1]

I am working on the top end of one now on a SX. It's tight but you don't have to pull the engine. Spent more time trying to get the exhaust apart than anything else. Piston, rings and cylinder installed today but if I had 150 psi, Id leave it alone.