Working on a 1998 Polaris Sportsman 500. This thing had a couple of unusual problems that baffled a few good techs. Got the starting problem, previously posted, repaired and now starts like new.
I tested this ATV with the air box removed, ran like a scalded dog at high speed, pulled some impressive wheel stands, awesome power and idled like a Cadillac. Put everything back together and it bogs badly in neutral or in gear, won't rev up.
Removed air filter, same problem. Removed air box, ran like new again.
Replaced the carb with a direct factory replacement. Float level correct, choke and throttle cables adjusted to specs. I removed the air intake tube from the air box, checked for obstructions, there were none. About 2-1/2" on the filter side and 1-1/2" on the carburetor side. I can rev the motor to 3k or 4k RPM's, slip the air intake tube over the carb air inlet and the motor practically dies. Remove the intake tube and the RPM's pick back up almost immediately. The original carburetor did the same thing and was replaced because of this.
Is it possible for jetting to be this far off on a factory replacement carburetor?
Anyone have any ideas?

 

Is this a real factory carb or an aftermarket replacement carb? If aftermarket then yes the hets and other settings could easily be way off.