This past weekend i was riding my Sc400 when it started cutting out i thought at first it was fouling the plug. when I got to the house I noticed the temp light was on and the fan was blowing. I let it cool down and tried to start it. It just backfired through the tail pipe and it would not start. You guys think it is the rings and what do you think it should cost for a rebuild?

 

Sounds like your rings have stuck and you have scuffed the piston. You have lost just enough compression to prevent starting. But usually they backfire through the carburetor.

Wow, two clutch jobs and now a cylinder hone and piston/ring replacement. Ouch!

Were you running special jets and a K&N air filter?

In Minnesota we had a rash of "meltdowns" on snowmobiles because of inferior fuel. It has been very hard on the manufacturers to increase performance every year with the quality of fuel available. As a precaution, we have all been told to burn premium in our machines around here.

 

this thing is totally stock it has been a mess from the get go luckly the clutch jobs where under warnty i love the machine when it runs like it is suppose to but its been a real headache. The honda still has no problems. the fuel thing may be a concern thanks for the tip. i was also wondering about the oil injecting system the light never came on and the resovior was full but i just don't trust it as much as a self mix you know it is getting plenty of oil as long as you mix it right.

 

Pull the spark plug and perform a compression test, put a little oil in the cylinder and test it again. If there's a major difference in psi, the rings are cooked.
If you're going to have it apart, do yourself a favor and put a Wiseco piston in it while it's easy. You'll save some heart ache down the road.
I put one in when the stock piston went south.

 

can the cylinders on the SC 400 be bored or do they have to be sleeved it is a 2000 model anyone know?

 

CEET400ex,

They make pistons for the 400 series from 83mm all the way to 88mm. That's .140" over. Yeah I think you can find just about anything in between.

They can be bored out to .080 with out any harm. Although with the larger pistons you'll have to get a big bore kit.

 

Just curious,

In the snowmobile arena, the users of Weisco pistons regret that they did not put the stock pistons back in after a meltdown as the Weisco pistons expand too rapidly after the engine starts and can cause a "cold seizure". I guess this is not a factor in atv use.

 

Thor the arena racers propably do not allow the machine to get warmed up that will happen to all two strokes machines regardless of brand.