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So I had a thought cross my mind the other day while I was out riding. I felt like my CRF450X was backfiring a bit more that usual. Part of that is because I'm still trying to iron out the fuel screw/idle screw mixture but that still makes me wonder: Does the season change effect your jetting? If it does, I'd imagine it would only be minute? What do you guys think?

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Yes season affects jetting 

how much depends on how big of change 

Edited by kxrob

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Any change in air density, regardless of the time of year, will alter jetting requirements.

On a four stroke, you have to change it pretty drastically before actual jetting changes are required : EG from 2,000 ft to 8,000ft elevation.

Daily density issues can be addressed with the fuel screw. It usually take less than 1/8 of a turn to re-adjust the idle mixture correctly. 

If your bike is actually back firing ( a loud ocassional big, loud bang upon decelleration) vs. deceleration 'popping' (everytime you shut the throttle you get popping; more popping the lower the gear you are in) they are two completely different senarios.

Decel pop is a lean condition, usually caused by an air leak (intake boot, exhuast flange crush washer, missing fuel screw oring, etc) or a poorly adjusted fuel screw. You should always have a little decel popping, otherwise you will be too rich right off idle, and you will have poor throttle response.  With most 'track't bikes some decel pop is normal.

Backfiring is an acumulation of un-burnt fuel in the combustion chamber or exhaust that explodes post-combustion. Usually caused by a worn out valve/seal/seat/plug that is causing incomplete combustion. It can be large enough to force the pipe to crack/split.  

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Your owners manual may have a jetting chart that clearly addresses changes based on altitude and temps.  My CR does and it does make a noticeable difference.

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Your owners manual may have a jetting chart that clearly addresses changes based on altitude and temps.  My CR does and it does make a noticeable difference.

I'll have to look at what my JD Jetting kit says. If I remember right, the only big change would be to change the needles for really cold weather. Maybe change try changing my needle position? Honestly, I'm really not too worried. Not a big summer rider, just waiting for the rain!

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