Buddy of mine just put on white bros e-2 slip. Came with main jet and nozzle, no needle. Runs great but it tends to back fire when he lets off the throttle. Any idea? I was told air fuel mixture.

yfz450 help

GLAMIS Labor day weekend, I told my boys they are crazy, “ it’s too HOT” but we r going wish me luck….

 

Yea he needs to turn his idle (i think pilot, only external adjustable) jet clockwise. That will cut off some of the fuel flow when he lets off the gas and it goes back to idle. Go in 1/2 turn at a time.

 

You mean it came with a main and pilot jet? Unless he has an '06, the needle has an adjustment on it, he could most likely lower the clip one notch and that would help with the back firing(which is a lean condition at idle/low throttle by the way.) If setting the fuel screw to more than 3/3.5 turns OUT, then he should also go up on the pilot jet and then readjust the fuel screw back in. Just because the company gave you a jet doesn't mean it is the right one for your altitude and state of tune of your engine. White Bros is just making an educated guess based on thier own testing.

 

thanks guys, i'll let him know.

 

What size main and pilot is he running? The pilot jet is mainly for starting. If it starts easy, I think you'd be into the main jet or needle especially if the needle hasn't been touched. Jetting is a funny monkey. It's like getting a combination lock without the combination. They get ya close, but the rest is up to you. I got the NCVQ needle for mine and it's very common when rejetting the yfzs. Ask for the yz45f dirt bike needle. Some parts people will look at you like an amish person a Circuit City, but just remember NCVQ. Good luck.

 

Backfire can many times be taken care of by backing OUT the fuel screwa 1/4 turn at a time.

Don't go more than 3 turns out though..