Just replaced the factory airbox cover with Outerwears fabric airbox cover. Noticeably improved throttle response and a different sound. The bad news is I'm getting mild backfiring when I release from full throttle. I did nothing to the jetting yet. What does it need? Did the lid change lean it too much? I ride from 4500' up to 13000'. What jetting should I have? Merry Christmas, Roostin' New Year.

 

Backfiring when letting off the throttle generally means a lean slow jet. You should try turning the air/fuel mixture screw and see if that helps. On my nieces, I bumped the slow jet up to a 40 (stock for my elevation is 38). It cured the backfire, and also made it alot easier to start when it's cold.

Brian

 

On my 400ex I bumped up to a 155 main and a 40 pilot and it helped some but it wasn't until I adjusted the needle that it all went away. The meat of the throttle from 1/4 to 3/4 is the needle the first 1/4 is the pilot and the last 1/4 is the main. The mixture screw helps somewhat I turned it out 1 turn more than stock but it helped it idle better more than it helped cure the let off back fire. If you go to the forum at exriders.com you'll find a boat load of people with honda experience who give good advice.

 

I just piped , filtered and rejetted my wifes 02, first let me say WHAT A DIFFERNACE, i set up jetting for stage 2, with the airbox lid off, used a 104 dynojet main, ANYWAY... it was backfiring, so i played with all the adjustments and i tried it with the lid on and off, which are two WAY different air mixture settings, and it backfired both ways, so it is not due to being too rich or lean, just due to the less backpressure of the aftermarket exhaust system.
jetjock16.

 

Back firing during let off is a lean mixture if it is doing this when you let off and not when you accelerate try changing the needle setting on notch richer. If it is during exceleration and it "stumbles" then it is to rich. Check your sparkplug color.

Black = too rich
Brown = just right
light color (white-ish) = to lean

I couldn't fully get rid of let off backfire until I adjusted the needle.

Basicaly you have increased exhaust flow and not your trying to increase air flow and fuel flow to match it. It shouldn't backfire if these are adjusted right.

 

If you are using a K&N which flows way more than the stocker it could be too lean with the lid on which means it will definitely be to lean with the lid off you could very likely have a situation of lean and leaner.

 

lean and leaner, thats a good point, but i also tried blockin off 90% of the airflow by coverin the filter with both my hands and it still backfired when lettin off the gas, ill try the next richer needle setting,
thanks
Jetjock16.

 

Let us know how it turns out for you.