jetting maybe????

[400exride.red]

ok i guess its been a while since i wrote in here i got a small prob heres what ive done. White bros slip on, ground down welds on stock head pipe, no lid on air box, cam ground by delta camshaft ,base gasket removed, xr 400 head gasket ,dyno jet jet kit w new neddle in 3rd from top slot, and 155 jet and light clean up of head "hobby port i guess" .
Ran it w all the mods and a 135 jet and it was back firing now w the 155 it is better butt still a little back fire butt only on decel when i let all the way off the throttle from full load . any help would be appreciated. Thanks in advance.

[stupid driver]

backfiring usually means your runnin lean. try maybe the next size main, and adjust your air screw out some.

[400exride.red]

thanks for your help ill try that tommarro any one have any idea what my new comp, ratio might be w no base gasket and xr head gasket??? thanks again

[stupid driver]

stock is 9.1:1 if i remember right, so you are probably lookin at 9.5/9.6:1.

[cals400ex]

for the popping on deceleration, i bet you can fix that by simply turning the fuel skrew out some. if that doesn't do it, you might need a larger pilot jet or you are possibly even lean on your needle. in the colder months of the year, i find my bike to run better with the clip on the needle in the 4th position, not the stock location. i don't know dynojets, but from what i read i bet a 155 is plenty big. i think many people on here run the 146 or so with their piped/filtered bikes, but don't quote me on that.

[400exride.red]

put a 160 in it today and turned the idle screw out just bout a 1/8 turn made a world of diff now no popping or nuthin runs great thanks for all the advice

[cals400ex]

glad you got it figured out. if it seems to be a little slow in the upper 2 gears, i have a feeling your plenty big on the main. if anything, do a plug chop. i have a feeling that 155 dynojet is plenty big, but as we all know, jetting is trial and error.