From what I read and on FMF website u can use a 42.5 pilot jet (stock) and 1.5 turns out on your Main jet and a 152.5 or 150 main jet with the needle clip on the 3rd position. It may be different with an HMF pipe though. buy a few spark plugs and do a plug chop once you jet it. You could use a 45 pilot and see how it goes. Also make sure your carb is clean and the float height is set correctly.