Popping in deceleration - XR650L

The problem was already there, but after cleaning up the carb with one of those spray carb cleaner (I removed the filter and sprayed it inside, while idling) it got MUCH worse.

Now the bike pops every time I close the throttle. Very annoying. And loud.

1) Is it dangerous for the bike?

2) Where do I start?

Have you done the uncorking mods yet? They all pop on decel until that has been done. Not sure why it would have gotton worse after cleaning unless you knocked some trash out and it's letting in more air.

Concur that seom debries was dislodged and is now possibly obstructing flow and making things worse.

Not that it is of much help but I went t a UNI foam filter from stock paper on my NEW 05 650L and it runs better! no other mods done at al - no rejetting, no snorkle removal nada - and the popping back on decel is much less!!!!

some carb cleaners are rough on certain rubbers and plastics ... always rinse yer rubbers ... :)

Hi gimgim,

I personally don't believe in any magic cleaners you pour into an engine or carburetor and everything is clean. Like jlpskydive said, it might have loosened some gum that sticks now onto something else. Or like roadcam said it wasn't to nice to those rubber diaphragms.

I always had the best results by taking the carb out and clean it manually. That way you might also find other defects.

I don't know about other XRL but mine didn't pop without mods and doesn't pop after finishing all mods (jets, filter, exhaust, smog pump)

That popping comes from unburned fuel/fumes that makes it through the engine and collects in the exhaust. If there is enough of that stuff and your engine fires it ignites that stuff and makes that popping. Personally I would say it’s not to bad for the engine but mainly annoying.

Much worse is when you do it on purpose by using the kill switch while the engine and bike is in gear to force the collection of unburned gasoline in the exhaust. Makes quite some bang when you turn the kill switch back on after a few dead revs but also blows back into the engine and might damage valves and head gaskets.

Anyway, you want to find the part in your carb that doesn't shut off the fuel during deceleration.

I would check the float level first and the needle if it is still sealing to make sure the bowl doesn’t overflow and cause it that for to get to much fuel. Maybe a slightly leaking choke has the same effect.

The second thing is that little can on the right side of your carb. I actually plugged off the vacuum port when I removed the smog pump and that was why my XRL started popping like crazy. I found out later that that was totally wrong. After reconnecting it the popping was gone completely.


On that picture you see a rubber plug on the hose connector. That should go to the front of the carb and over a "T" to the smog pump. Make sure those hoses are still OK and clear. You might want to take it off at that side and check if you feel any vacuum while the engine is running. If not investigate that hose harness for blockage/damage.

If that checks fine, you might want to look into that can on the side of the carb. It has a spring and diaphragm inside which is supposed to cut of the fuel during deceleration.


Should be number "9" on the diagram. Make sure the diaphragm is in good condition.

If you have compressed air available blow through all holes the make sure those are clean as well.

For me a thorough cleaning fixed most times any problem I had with a carburetor, even if I couldn't find any visual problems....

Good luck,


Take the carb apart and clean the jets, Make sure its jetted right, Not to lean...

Thank you for your help. I haven't had the time to uncork the bike yet, I guess now it's the best moment, since I have to take apart the carb anyway. I've just ordered from Baja Design the jets, the UNI filter and the smog kit. Everything was $104 (any cheaper online store?)

I hope the problem is caused by dislodged debris and that I didn't do any damage to the carb plastic with the carb cleaner. I'll be away for two weeks, when I am back I'll uncork the bike, clean the carb and let you know


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