hi i have a question for you guys. today i was riding my scrambler400 in the snow and it just shut off, just like i hit the kill switch, but i didn't. when i hit the starter the motor turned over very fast with no resistance at all, thought the starter gear broke so i pulled the pull starter and it was like it wasn't hoohed to anything but the engine turned over, then i realizede that there was no compression. i hit the starter again and i could barly feal any air come out of the exhaust. this engine just had a new topend 10 hours ago so it isn't worn out. what do you thing the problem is, any advice will help , thanks

 

Sounds like it was run lean and melted a hole in the piston.

 

This may sound stupid but: the sparkplug didnt come out did it?

 

no the plug isn't out. but earlier that day it would bogg down like it was lean, but not too bad thanks

 

SPORTSMAN70003 you were exactly right i took it apart and there was a hole the size of a pencil on the edge. then while i was taking it apart i found that the temp light wasn't hooked up at all and the top piston ring was melted to the piston. i wasn't riding it while it died my 11 year old cousin was riding it. i wish that i was on it so i could have shut it off earlier when it was bogging down. the cylinder is scraped up prety good. will bore it out evean more. when i fix it do you think that i should sell it right away or will it last a while. are these motors any good with a wiesco piston

 

I just rebuilt a friends 400 Sport not to long ago it had a small hole melted in the piston. I would put a Wisco piston in it if I were you. Also you need to go bigger on your main jet. It dosen't take long to burn a hole in the piston if you run it lean.

 

ya it took about 7 hours to burn a hole. is it hard to change the jet

 

Its not bad just take off the bowl on the carb and you can get to it from there.