Blaster probs and advice

[BlasterMod6]

I have a 92' blaster, fatty pipe, and powercore 2 muffler, its bored at .060in over and boyeson rad valve. I keep backfiring after lettin off the gas in 1st and second, lettin off from redline, I have a 270 jet because I took the lid off my air box, and I started mixing at 40:1 is that too lean?

[Kane]

Backfiring usually means theres a leak in the pipe somewhere. Sometimes, it can mean you're a little rich, but I've seen that mostly on 4-strokes.