popping noise after deceleration after removing air pump

well i have rejetted 2 times bigger pilot forget size(one that came with gytr air removal kit) and have went 170 main, still popping!!! bike runs awesome but the pop has to go!!! i done the full gytr air removal kit, except for holes in airbox. i posted before and had lots of replies obout the jd jet kit. does this totally eliminate the pop?? i dont want to have to take the carb off again.like i said it rips!!! but that popping is gettting on my nerves bad!! will the cut out in the airbox help?? i got a 172 jet coming was gonna try that. thanks guys!!

well i have rejetted 2 times bigger pilot forget size(one that came with gytr air removal kit) and have went 170 main, still popping!!! bike runs awesome but the pop has to go!!! i done the full gytr air removal kit, except for holes in airbox. i posted before and had lots of replies obout the jd jet kit. does this totally eliminate the pop?? i dont want to have to take the carb off again.like i said it rips!!! but that popping is gettting on my nerves bad!! will the cut out in the airbox help?? i got a 172 jet coming was gonna try that. thanks guys!!

air leak somewhere in the exhaust? 172 seems big, maybe a 168 or 165? Excess unburnt fuel will pop on decel, especialy if it gets some additional air.

Check the plug on the exhaust port for a leak. Also make sure the header bolts are tight. Its gotta be an air leak somewhere.

I just installed the gyt-r kit on my 2006 wr450--stock main jet--and it does not pop or backfire at all.

In Australia the AIS is completely removed before it leaves the dealer ... there's no need to have them here by law !! I am running a 48 pilot, 172 main, Yamaha racing needle on clip position #3 and a zipty FS at 1 3/4 turns out. with almost zero popping on decel

n.b. - I ride from 0 ~ 5000' in Australia and with a GYT-R exhaust (mmm)

1. Are you sure that the needle you are running isn't that stupid 'one clip position' thing that the bike comes with - it is pretty lean and a good idea to get rid of it

2. There may be an air leak (air boot, exhaust flange or AIS ports) causing the bike to run lean (and pop) and possibly a little warmer as well

3. This is trivial but important - you must make sure that the carb sits level because if it leans a little to the side and your float is adjusted near its maximum it can cause popping/flooding and difficulty in starting - this i know from experience (and a clever Yamaha service tech !) - the difference is noticeable (especialy starting)

Good luck trying these suggestions ...

There must be a leak somewhere. Removing the AIS should eliminate the backfiring, not make it worse.

i guess i need to check for leaks, i do know that i have had the muffler off a few times, swapping between a yz muff and the stock wr, i will check today for intake and exhaust leaks.

I have 05 wr450 w/JD kit and the free mods. I can't seem to totally eliminate the popping also. I still have the AIS system on--so this may be my problem. Some days it pops on decel more than others. Sometimes it doesn't do it at all. I'm sure this is temperature and humidity related. Like yours, the bike rips, starts well, and has little/no bog issue. Unless you rejet often to accomodate changes in temperature, you may never totally get rid on the popping. Some of the veterans like Indy may have more to add on this topic. :thumbsup:

You will NEVER eliminate the popping with a properly jetted bike....it's caused by the high vacuum created by decel on a closed throttle. That richens the mixture but doesn't let in enough air to burn the extra fuel. When the fuel-rich exhaust gasses hit open air, the fuel ignites, creating the popping noise....live with it!

If you watch road racing, motorcycle or cars, you'll see flames coming out the exhaust as they enter the turns-same issue....live with it!

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