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Popping on deceleration

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I have a fuel injected 2013 kx250f, my first bike 4 stroke and FI bike. I went to the track this past weekend and by the end of the day when I would let of the gas coming into the corners it would start popping. It would only do it on deceleration and not if I pulled the clutch in. Thanks for all the help.

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Generally that's a lean condition on a carbureted bike. Do you have a pipe or header? I'm interested in this as well because I just moved to FI. Don't know if we need to get remapped or what. I'm scared to get aftermarket stuff until I know I'm going to have to pay to get remapped.

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It's stock exhaust. From everything I've read and researched it is still a lean condition it's adjusted with the TPS using a special tool that is a basically a wire that plugs into it so you can use a multimeter to read the voltage and move the TPS like a distributor in a car to increase or decrease the voltage which is how lean or rich it's running

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There's ways to test that to without that write, but it just adjusts timing. I don't think it will do anything to the actual amount of fuel. I think it could have an affect lean or rich but I don't think it would be much in terms of lean or rich. I honestly don't know though on Fi.

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Me either, everything i keep reading says that adjusting it by .02v up will get rid of popping on decel. I cant find much on it though

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Same situation on my 13 kx250f. Would love to know the fix. Stock pipe

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I have this issue with a 2012 model. Was able to minimise it by setting the TPS as per the manual. It is still there though. I read somewhere that it can be caused by a leak at the exhaust header pipe. This introduces enough air into the hot pipe to ignite the unburnt fuel in the exhaust. I'm not getting huge backfires, just popping. It gets worse if the bike is hot.

I might get a new header crush washer and see if that helps.

Damien.

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I have since got a new crush washer for the header pipe to cylinder joint. (Was hard to get one, only made oem) The popping on decel is now completely gone.

Anybody still trying to remedy this should try a new crush washer. It's probably the cheapest part you could buy for your bike ,so worth a shot even if it doesn't work for you.

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Happy to see you have it solved.  I was about to post that: where I come from, some people pay a lot of money to just get their exhaust to rap louder and pop and spit when off the throttle ;)  They like the raspy sounds.

Otherwise yes, the cause of popping on decel is unburnt fuel flashing off in the hot header pipe right at the bend.  It is often red hot right there.  The cause is spewing unburnt fuel and that getting some air combined with the hot pipe to light it off.  It is absolutely normal as for example .... The scenario that sets this up is when just a really givin' - 'er hard and then chopping the throttle.  For a split second the engine is grossly overfuelled and super rich with the air suddenly chopped (carb closed).  That unburnt fuel exhaust dumps into the hot header.  If there is an exhaust leak for air to get sucked in as the gases cool and contract, the air gets in and air+fuel+hotpipe and boom - PoppatopityRappatata.     You solved it by eliminating the air source by changing the gasket.  However, my point is the condition still exists through normal riding/operating.  So if anything, and if the pops come back, you know the cause and it is nothing to be really worried about - so long as the bike is otherwise running fine.

 

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