When i hit the throttle on my 07 450, it will sputter then rev. Please help me on this. I heard this has something to do with the fuel/idle mixture. I also know that the stock fuel screw is not adjustable and you need to get a longer one with a handle to adjust it.

 

Your stock fuel screw is VERY adjustable. You just have to know how to get to it. With the right tool you can adjust it all day long.

All the aftermarket screw does is make it more accessible. Much easier to adjust with the aftermarket screw for sure.

Buck

 

i dont know about the fuel mixture screw...... but i know there is an aftermarket accelerator pump cover......its supposed to increase the flow to keep up with how fast the engine revs.....i think boysen makes it.....i think its around $60 bucks......i have a couple of friends with yfz 450s.....and i know what you mean by it bogs and then revs......really bad in stock form.......the cover seemed to fix the problem on theirs.....