250-500cc Another Piston Thread

Nice graphics. Where they come from?

I'm glad to hear that. My next piston might be a weisco. I think they are better than cast as long as you give them enough clearance and don't rev the engine until everything is fully warmed up. Losing tractor mode is a good way to describe what a tired top end feels like.

So I just took my first top end apart. It's an 09 WR 250. PO said he bought it new in 2011 and raced C enduro Vet for 1 or 2 seasons. Has 97 hours on hour meter now plus he said maybe 40 more before meter. I'm a trail rider that doesn't get 'on it' too much.

I figure now's a good time to give this a try, especially after reading this thread. Piston and cylinder look good to me but what do I know.

Measured bore with cheap Lowes caliper and get 66.4 mm. It's a C size cylinder.

I didn't buy parts yet but think I'll go the same route as Huskynoobee with the Wiseco. Wish me luck!

Looks good piston especially!

Should I just do new rings?

What does the intake/carburetor side of the piston look like?

Man my stuff is never that clean!
May need to start importing interceptor.
Cheap calipers will struggle to accuratly measure the bore ideally you need internal bore guage, look like a T with telescopic arms.
Personally i would do rings an whop it back together.
But if your more safe then tight go piston kit with small end.

No do it properly don't be cheap might bite you in the arse!

Yeah, I usually take the cheap way out then regret it later. The presidents squint when I open my wallet!

I do use Interceptor. I had to order it direct from Amsoil since nobody around me carries it.

Here are some photos of the piston. That one face is the intake side.

That piston looks good. I would still replace it. Then you should be good for a long time. What oil/ratio are you running?

I run 50:1. Straight Super pump gas.

I don't race and don't ride a ton so that's probably why things are in good shape.

When we ride we go a lot of slow single track and fast dirt roads.

The intake side is the weak link on the WRs, yours is showing the first sign of wear, if I were you I'd replace the piston because when it gets to a certain point it will go fast and the savings is not worth the risk.

Thanks, done deal. I'm going new Wiseco, bearing, and gaskets.

If you look at my Nov 11th thread "Should Have knocked on wood" you will see pics of my wr250 top end with over 300 hours on it. It looks very similar to yours and was run on Dominator and Interceptor, I replaced the piston.

Just finished putting mine back together. Will start it tomorrow and begin break in procedure. Piston had very little blow by & just a little wear on intake side. My piston to cylinder clearance was .0031. Now at .0023. Should be quieter and hopefully the knocking sound while lugging will be gone. Picked up lots of pointers from this awesome forum Thanks guys!

Placed my parts order about 30 minutes ago.