06 yz450f backfire

I have a 2006 yz450f i got about 3 weeks ago it had no spark so i fixed that now it runs its just that on deceleration it backfires quite a bit i know my problem lies in the carb im just wandering what i should change. Needle position, pilot jet, main jet. I don't know any help would be appreciated.

Thanks

my 04 did the same it was running lean poppin like crazy when decelerating. i just richend the air fuel mixture screw at the bottom of the carb and now shes a little rich . but i think thats better than lean

usually main or pilot jet up 1/2 sizes will fix this. if not, then there's air getting into your pipe

I have a 2006 yz450f i got about 3 weeks ago it had no spark so i fixed that now it runs its just that on deceleration it backfires quite a bit i know my problem lies in the carb im just wandering what i should change. Needle position, pilot jet, main jet. I don't know any help would be appreciated.

Thanks

I would start with exhaust leaks, particularly at the joint where the head pipe meets the tail pipe. Carb might need some work, but if it's running good other than the poping it's most likely exhaust. There is a jetting database in the sticky section that is really helpful to get some idea for jetting at your altitude.

Ok thanks for the help I try doing this tonight

stock come with 42 pilot, which is why it pops on decel (too lean).

I bumped mine to a 45 and its better but still has some pop. I have since bought at 48 and havent put it in yet.

Ton of posts here and magazine articles on what is needed to fix the 2006 jetting.

Once again, a correctly jetted and tuned YZ450 should pop off some on deceleration. It's just a natural characteristic of certain engines. Most people who have fattened up the idle circuit to completely eliminate all of it discover that their bike runs a bit dirty or stalls more readily on sudden throttle chops from low RPM loads.

Popping a couple of times on most decelerations should be considered fairly normal in most cases.

http://www.thumpertalk.com/topic/204354-all-yz450-jetting-specs/page__st__20#entry2683126

Well I checked the timing on it and it was way off at tdc so I changed it to what the manual says tool me couple tries but I got it so I fired it up and it ran for about 10 seconds then it died out made a weird noise and it would only run on choke when it did run. Any ideas?

Had the same problem on my 400f. I took the 45 pilot out and put in a 48 works a lot better now but still likes the choke a bit till it is HOT. My fuel screw is anywhere from 2.5-3 turns out from lightly seated.

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