I still have stock jetting on my blaster. When I give it gas, it sputters and sometimes backfires. What size jets should i try? Would a 260 main jet be to big? I am at sea level. My mods at down there in my sig.

 

What temps are you running at and whats the size of the main jet now.

2000 SCRAMBLER 400 2X4

SCRAMDADDY400

 

sounds like its getting too much gas, as if you diddnt know that already.. but... you should have rejetted it when you put the reeds in, and the pipe, and the oversized piston, Id definetly get it fixed asap, back firing isnt good, hard on the reeds, if one breaks and it backfires through the carb you could have a flaming situation...