Took machine to dealer,turns out the piston is scuffed.
Dealer feels ther may be a problem with oil injection pump,doen't think it got to` lean and hot.There is no sign of melting apparently.

Going to a wiseco piston 20 over.
Has any one heard of this problem? Considering eliminating oil injection and going to premix.
What ratio oil to gas would be applicable.
Also considering v-force reeds and larger carb,how much difference would these make and is it worth it.
Am i sacrificing reliability with the modifications i've made?
Any comments welcome.

 

Hey there you say the piston is scuffed? It sounds like it is from a cold sizure or commonly called a four corner score. This is caused when the piston heats up and expands faster then the cylinder bore. Do you let the engine warm up before riding ? Or do you get on and go?

 

Allowed engine to warm prior to riding.

 

Boring doesn't take away in reliablity.

My blaster is bored out 60 over. And i don't have any trouble.

Do you really need to bore? I was able to just hone my blaster out after the oil injector failed. And the piston was more than just scuffed.
http://www2.1st.net/ar15/pistontopside.gif

 

Most of our 2 stoke piston scoring problems are cold seizer related. I agree with the above post. Warm it up before you get on it.

 

tooscrambled,

I've had the very same problem as you did. I was at Cochranton at the time. There is one thing you must remember with the Weisco piston, this piston is even softer than the original cast piston and is more likely to seize than it's stock counterpart. The thing I'll be doing from now on is to start my quad, let it idle while I put on my riding gear and then ride slowly for the first couple of miles till the engine heats completely. I don't want to go through another rebuild again.

 

Engine idled approx 5 min while I suited up,rode approximately 15 min seldom over 1/2 throttle prior to lettin her rip.

Is this enough warm up?

 

Hmmmm,

Did the top of the piston look melted or damaged? If not, the only other explanation is excess piston clearance. The piston is only supposed to be about .003" smaller than the cylinder. if the cylinder was for some reason over .003" larger it could cause the piston to scuff, resulting in a seizure.