my son has a 99 polaris 400 sport 2 wheel drive that ran fine off the trailerat the local trailhead but died and will not start again turns over fine has spark. fuel I can get a little pop out of it once in a while but nothing more.I also checked the piston and it is fine also. any one have an idea to help us out I'm kind low on repair funds and he is 15 so no help there.he bought it himself we are looking to fellow atv'ersfor help
Thanks

 

you said you checked the compression and it was up there right? did you check to see if the carb was dirty. make sure the air filter is clean and vent lines are all clear and not pinched.did you try putting some gas down the plug to get it to fire up? just some idears to try.

 

Do a compresion check.It needs to be at least 100psi to even start needs to be 120+ to run good.Try a new plug?

 

yes,we tried a couple of new plugs it seems to be getting good fuel and putting gas in cylinder gets just a bigger backfire we will try the comp test and get a reading of that. when it ran off the trailer it was running a little rough then slowly died, you know started to slow down and smoke a little more but on a 2 stoke I thought a fouled plug. could a bad ring cause this?

 

yes it would allow oil to come up and soak the plug. check to make sure the float isnt sticking open causing it to get too much gas. if it wasnt set correctly this would also make it run rich causing plugs to foul.

 

rings will cause this

 

check compression -- thats how they act when they stick a ring .

Rick

 

we will try the compression test, by a stuck ring is that meaning a broken or cracked ring ? also the cyclinder looks good no big scratches or marks
Thanks for all the ideas and insight into what could be wrong.

 

well here's the news on the compression test I'm getting 30 psi so i'm guessing she is junk. the question is, is it worth rebuilding? anybody have a guess on how much this may cost to rebuild or should i look for a used engine or maybe sell it off for parts?any insight would be helpful thanks.

 

hard to say w/out knowing what is causing the low compression. broken ring. scoured cyclinder. if you rebuild it at least you know what you have vs. buying a used tired engine that wont last either. 2 strokes are a rol of the dice when buying one used. once its apart you could tell better.