Hi there I am new too this forum, but I here it is the best. I have a Polaris sportsman 500 running very lean. It is completely stock. I have upped the main jet to a 167.5, moved the clip down one on the needle, rebuilt the fuel pump, changed the fuel filter and the spark plug. From idle to 3/4 throttle is good, it is full throttle that it lags. The spark plug is bright white. Any help would be awesome. Thanks in advance!!!

 

are you running in a cold climate?

 

round about 50-70 degrees!

 

is the air filter clean?

 

If you suspect that you're lean at WOT, then the logical decision would be to increase the size of the main jet.

 

What elevation do you ride at , 167.5 seems pretty rich for a 500 unless your at sea level, if the plug is white, i'd go up at least 2 sizes om the main jet.

 

The air filter is a brand new stock one with a pre wrap. I am only about 500' elevation. I just cant figure out why I need to go even bigger on the main. Stock 155 I went to 167.5 on a bone stock bike. I appreciate the help guys. Hopefully we can figure this out. Tonight I will bump the main jet 2 more sizes and see what happens.

 

Clean the carb thoroghly while you have it apart , put the needle on the middle notch. I just thought of what might be the problem, start it up and spray carb cleaner around the intake boot, it may be cracked and sucking air, that would make it real lean, check that before you do any more jetting.

 

kerbbirds is right that will happen. check for any air leaks around the intake seals to the carb.

Bill

 

Thank you I will try that tonight. It did not have an air box gasket so I replaced that. But I will try the carb cleaner trick. Thanks.