i just had a hmf slip on installed on my yfz450 and was wondering if its normal if it backfires when i let of the gas. it doesnt do it real bad unless i get on it hard then let off quickly. is it because my jettings wrong cause i read somewhere that if it backfires it means its running lean or is it just because of the pipe. any help would be appreciated thanks.

 

Did you rejet after the slip-on?

 

yea i had my dealer install it and rejet it

 

It sounds like you are a little lean. let the dealer fix it. Do you know what size jet and pilot they put in.

 

my quad does that too somtimes when i let off the gas at high speeds/rpm's, most people tell me this is normal its not real bad backfiring just a little popping. it shouldn't be a big deal. and im pretty sure mine is jetted perfectly

 

If it was jetted perfectly it wouldnt pop on decel. you might try opening the fuel screw a 1/4 turn or so to fine tune it. If you can live with the popping your probably ok.

 

My friend has a GYTR pipe on his and it backfires alot. We messed around with the jets alot and air screw. nothing happend, so we think its just the back pressure issue.

 

Check all bolts on header and clamps.If there loose and air is getting in it will make it pop on deceleration.Also check carb boots.