My 2001 Sportsman 400 suddenly doesn't like to start. We use it as a pit bike at the MX races. It may sit for 2 weeks and then when I try to start it, it only cranks and doesn't fire.
I have pulled off the air filter and when it cranks, gas will sputter and sometimes flow out into the air box. I have already installed a new needle and seat. If I let it set and keep trying to start it during the day, most of the time it will finally start, but maybe 3 or 4 hours after I try it the first time. Once it starts, it runs great and starts great the rest of the weekend.

The vacuum fuel pump seems fine. I am thinking it might be the choke "starting enrichment" valve. I have never worked on a carb with this, only the choke type or air restriction type valve.

How does this starting enrichment valve work? I have the service manual and the cable just looks like it has a plunger on the end. Does it inject gas straight into the carb intake?

Any suggestions?

 

sounds like it may be time for a complete carb rebuild

 

if its the plunger style choke.... it could be sticking but its not a fuel passage it a air flow mixture.....pull it out and make sure it moves freely.... but i do agree about the carb rebuild also...

 

I finally got it fixed with some augguestions from my local Polaris dealer. After teraing into the carb for 4 times and everything looking good, he suggested I disconnect the magic wire to the electronics. This rules out the throttle safety switch, kill switch, speedo, etc.

Once I unplugged the wire, the engine started right up. Turned out to be the speedometer. Cleaned the contacts on both conectors and it is back running great.