it's a posibility if the diaphram is cracked or warped/dry rotted it could be bad. it doesn't hurt to check it though.

 

Any idea were to get a replacement diaphram, I'd think that'ed affect the whole throttle range

 

i think the diaphram only controls the idel circut but i'm not positive. i would think you could order one online at bikebandit.com or worldofpowersports.com they have one in there somewhere.

 

I can't seem to get this one figured out. I tried moving the needle position both up and down, I tried adjusting the air fuel mixture. And i can't seem to get it figured out. It doesn't have a air leak that i can find (tried the W D 40 trick) The only thing i havent tried is changing the main jet, but the Yamaha service tech said that probably wasn't my problem when i went to pick one up. I think this one's going to have to go to the Yamaha dealer to figure out.

 

what size jet did you get? if you haven't changed the main jet yet i would do so. if it's spitting and backfiering at or around 1/2 throttle it's probably your main jet. the main jet controls 1/2 to full throttle. so i would try changing the jet first before you spend money out the ***.

 

I was going to put a 150 in. I got to talkin with the service tech at the dealership and he said that that probably wasn't my problem, but i think i'll put it in before i take it to the dealership. Thats my last option unless you got any more ideas. Thanks alot, i apreciate all of the help

 

not a problem, that's about all i can think of.... i hate to run out of ideas on you. but i would try the 150 main and see what happens. lets us know what happens.