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Discussion Starter · #1 ·
I cant seem to get my WR250x to stop back firing. I have a PC4 exhaust and FMF programmer set to 3,7,2.5,3,3,3 Ive tried adding more fuel but I still get backfires. I also cant hear an exhaust leak with a plug in the exhaust but I don't know how I would hear it over the engine.

Any ideas?
 

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Discussion Starter · #3 ·
Me. I just left the body panel that the tuner sits behind off and rode it around and messed with it for awhile I got the base setting I used off of this site. It normally only backfires if you are really riding it hard or if you are cruising with and hold the throttle in one position for awhile and then let off it immediately.
 

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Typically with a fuel injection motor (at least with cars) when you let off the throttle, it cuts off the injectors (and spark plugs too I believe) to save fuel. The popping is the unburnt fuel that's left over igniting on the hot exhaust. If you're running rich, it just means there's that much more unburnt fuel in the system. Maybe try leaning it out a bit (very carefully) to see if it helps but I'm not sure if there's a way to completely eliminate it.

DFCO - Deceleration Fuel Cut-Off aka pop-pop-pop-pop
 

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Discussion Starter · #5 ·
Occasionally I get the very loud gun shot type backfires when I'm cruising at a steady light throttle pace and let off. I get the DFCO when Im riding it hard I figured that might be from it being too rich but, from what Ive heard it seems like it might be a bit lean.
 

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Do you still have the AIS installed? If so that is likely the problem. I had the AIS on for awhile with a fuel injection programmer and full exhaust and it popped a lot on decel. Once I removed the AIS, it pops no longer.
 

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TOO lean........ that popping is from the cold fresh air exploding in the pipe, it can be because of being lean or from a exhaust leak... reseal it and try again.

Yeah, AIS.... Air Injection System..... meant to make the exhaust lean for emissions...............too much fresh clean air in that exhaust. Plug that off.....thought that would be the first thing you did......
 

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Do you still have the AIS installed? If so that is likely the problem. I had the AIS on for awhile with a fuel injection programmer and full exhaust and it popped a lot on decel. Once I removed the AIS, it pops no longer.
this is your problem.
i dont know if you have an o2 sensor on the controller you use. but if you do, it will never work properly if you have the AIS still on. that system allows fresh air into the head to help ignite unburnt fuel in the ehaust. so youre computer will get false readings and everything will be screwed up. even if you dont have an o2, AIS makes it backfire.
 

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Discussion Starter · #9 ·
I'm not to sure on the AIS but it seems like y'all are confident that that is the problem. My bike is kinda in a weird state, it was once owned by a mechanic at a local dealership who put exhaust and some other mods on it. He traded it in to a used car dealership where the owner rode it for a few months and put the stock exhaust back on because he thought it was too loud. Ill have to check out the AIS thing, I figured it had been done because I noticed some other free mods.
 

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All the ais does is allow fresh ai onto the exhaust area of the head. Unless ou have an o2 sensor, it shoulndt effect the bikes running other than the popping. When you gt into the autotune and if there are other programmers like that (im not sure there is) is where it will effect rich/lean. But the bike will feel much cleaner when it doesn't spit and sputter
 
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