I just got a set of looney tuned dual exhaust for my yfz 450 and am wondering if i need to jet up? I'm basically at sea level. I have a gytr header with stock muffler now and an exhaust cam and gytr air filter with stock intake. please help anyone with some info!!

 

I would say Yes you will have to jet up on your pilot and main. A questions, are you leaving the air bow lid on?. my suggestion would be to go to your local dealership and buy 168, 170, 172 & 175 main, and get a 42, 45 & 48 pilot and start experimenting. Listen for popping on decelleration, and missing on the top end, these are signs your jetting is off, looking at the spark plug is also a great visual sign.