I have a 99 Scrambler 400 with Hot Seat 12:1 head, RCR Porting, Wiseco Piston .040" over, Shaved Flywheel, Delta Reeds, K&N with Outerwear cover, and run 93 Octane fuel mixed 32:1 pre-mix with oil injector removed. I have the RCR airbox mod but always run with the lid on. The stock 34mm carb is still on the bike but it has been bored to 35.5mm by RCR. I have a 40 pilot, stock needle set on middle position, and 360 main. I adjust air screw every ride. I ride at 1000 feet and outside temperature last time I tested jetting was 85 degrees. My concern is the 40 pilot seems rich and the 360 main doesn't seem lean it doesn't seem to matter how large I go on the main I can't get the bike to skip. The plug color is light brown so that seems fine. If I engage the choke while wide open the bike will cut out a little indicating it is finally rich.

My question is could the reason I can't get the main to go rich is because with the mods I have the carburetor can't flow enough fuel no matter what size main I go to?

Also, there are a few others on this forum with similar mods. Any feedback as to what pilot jet size you are running would be appreciated. I think I can get away with a 35 and have done some testing in hot weather but I am afraid of what the winter may bring although I never ride in temps. lower than 40 degrees.

 

That carb is ok. But the carb you want to put on is a Keihn 39mm PWK carb. It will give the best power for the $$$. It is easy to jet and works great. And you won't beleive the gas mpg.Just ask how many Polaris owners have that carb on there modified Polaris 400's.