i have a 99 polaris sport 400. aeen top end pipe,v-force reeds,38mm carb and installed the green and blue springs from aeen performance. it ran awesome at first but every time i have ridden it the take off was getting worse. ive checked carb jetting,clutch springs,tried stock carb, still bogging off take off! so we installed new wiseco piston,porting,new top end and still bogging!
please help! we are lost. tried hot seat clucthes and still bogs! what else can i check? also i know while i was jetting i did get some bad backfires while cranking. could this have damaged the pipe? or anything else? seems like performance has went away gradually since. this was before i rebuilt the top end. now it still feels weak. what to do? before i carried the polaris to dealer i checked compression and it was 80 without throttle opened. they claim they got 125 before working on it but i said go ahead and rebuild anyway, now they havent checked it yet. but with new bore,piston,rings, what else could it be? 6-03-2000 now the dealer says the case is cracked. is that killing it?????

 

Since your lost i might as well try to help you. iahve one question. Have you did a compression check?

 

I had the same problem with my sportsman bogging out, turns out a vent line from the carb was resting against the pipe and melted shut. A little snip and I was running great.

 

Shockwave,

Your problem might be the oil injection. When you installed the new carb, did you follow the directions about the oil injector? I did too. The problem was that if I ran the machine at low speeds for any amount of time, it would load up and foul plugs like crazy.

The solution is simple. Either get your dealer to dial in the oil injector or get rid of it as I did. My Sport will now run cleanly at all RPMs. I used to premix at 40:1 with Polaris injector oil, but now I run Bel Ray at 50:1.

 

Mike is right about the injector mix. But, check all your carb vent hoses to make absolutely sure than none have come in contact with your pipe or have been crimped. I've seen a few like that already. 125 seems about right for a stock setup.