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Why is my XR backfiring on decel?

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I have an 07 650L that backfires on decel. What can cause that?

Thanks

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Factory exhaust or aftermarket?

And have you done many engine/carb mods to the bike?

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give it 1/2 turn on the fuel screw (out/counter clockwise) see if that makes it any better, if so but still not cured give it a little more. sounds like a leaning out issue. may want to increase your pilot jet size

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Carburetor or intake leak, lean jetting, or exhaust leak. Try idling the motor and lightly spray starter fluid or carb cleaner around the carb and intake boot.... If there is a change in the rpm there is a leak. Dave's mods seem WAY effective, an air filter, exhaust upgrade and matching jetting are always welcome additions! Good luck!!!

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Daves mods or a dyno jet kit work well.I opted for the dyno jet kit cause I didnt feelike runnin round lookin for jets and small washers...But thats just me..No more pop on decell..Who hoo!!

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also add a problem with the Air Cutoff Valve (ACV) to the list of potential suspects :banghead:

:)

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I just got the bike and it appears to be all stock, including having all the smog equipment. You've all given me enough to start the process of elimination!

Thanks :)

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when i removed my stock smog equipment it almost eliminated it altogether

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agree you should dump the smog equip and rejet for sure, uncork if yo ulike

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The decel pop is caused from the smog equipment.Remove it and rejet and you should be fine.(but not legal)Or leave it intact and block it internaly since you are in Cali.

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I personally think the popping can be more attributed to the lean condition than anything else. I completed Dave's mods (55/158 jets), added a K&N, and removed the intake baffle but left the somg equipment intact for months so there would be no drama when I took my licensing test, and my bike didn't pop on decel at all, ever. All the while, the factory mufler and smog equipment were still in place. Maybe my situation was unique.

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I personally think the popping can be more attributed to the lean condition than anything else. I completed Dave's mods (55/158 jets), added a K&N, and removed the intake baffle but left the somg equipment intact for months so there would be no drama when I took my licensing test, and my bike didn't pop on decel at all, ever. All the while, the factory mufler and smog equipment were still in place. Maybe my situation was unique.

the smog (PAIR) system injects air into the exhaust ports on decelleration...effectively leaning the exhaust gasses and potentially causing backfiring, popping, etc...it's basically a controlled air inleak in the exhaust :banghead:

removing the system and/or increasing the idle and off-idle fuel (pilot and/or fuel screw) will minimize this issue. :)

:banghead:

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