what is decel pop caused from?

groggylbc
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groggylbc
and is it bad?
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mattyhamz2 4/10/2019 4:18pm
4/10/2019 4:18pm
Could be a few things.

Did the bike sit for a while with fuel in the carb?
harescrambled 4/10/2019 6:01pm
4/10/2019 6:01pm
groggylbc wrote:
and is it bad?
decel pop is caused by a lean condition during closed throttle conditions. It's not typically harmful. Is the bike fuel injected or carbureted?
Paw Paw 271
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Paw Paw 271 4/10/2019 7:12pm
4/10/2019 7:12pm Edited Date/Time 4/10/2019 7:12pm
This lean condition spoke of can be from dirty jets in a carb, dirty fuel injector, incorrect TPS set too lean, but the one thing that I see most is a bad exhaust gasket where the pipe mounts to the head. Most of these are a crush style gasket that folks want to reuse after the pipe has been removed, but in fact will leak when reused and cause this issue. If left uncorrected it can do harm.

Paw Paw
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groggylbc
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groggylbc 4/10/2019 9:53pm
4/10/2019 9:53pm
mattyhamz2 wrote:
Could be a few things.

Did the bike sit for a while with fuel in the carb?
2014 ktm 350

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mattyhamz2 4/10/2019 9:55pm
4/10/2019 9:55pm
mattyhamz2 wrote:
Could be a few things.

Did the bike sit for a while with fuel in the carb?
groggylbc wrote:
2014 ktm 350
Read Paw Paw’s comment. He’s the man when it comes to this stuff
Freddyfred
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Freddyfred 4/11/2019 7:21pm
4/11/2019 7:21pm
I need some more info on this too please as I figured the amount of fuel at idle speed was too rich.
I've had a bad case of decel pops and gone down 2 sizes in pilot jets plus decreased the idle screw. These things has almost removed the decel pops but when starting the bike it still smokes a lot and I get spooge pushing out between the cyl/pipe. When lean it's more of a rushing sound and a longer increase in revs right? What I get after letting go of the throttle when revs are high, is pops that makes the revs climb slightly just after the pop and then decel rapidly again.
Paw Paw 271
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Paw Paw 271 4/12/2019 9:56am
4/12/2019 9:56am
Freddyfred wrote:
I need some more info on this too please as I figured the amount of fuel at idle speed was too rich. I've had a bad...
I need some more info on this too please as I figured the amount of fuel at idle speed was too rich.
I've had a bad case of decel pops and gone down 2 sizes in pilot jets plus decreased the idle screw. These things has almost removed the decel pops but when starting the bike it still smokes a lot and I get spooge pushing out between the cyl/pipe. When lean it's more of a rushing sound and a longer increase in revs right? What I get after letting go of the throttle when revs are high, is pops that makes the revs climb slightly just after the pop and then decel rapidly again.
Are we now talking about a 2 stroke?
What bike?
More info needed.

Paw Paw
Titan777
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Titan777 4/12/2019 11:40am
4/12/2019 11:40am Edited Date/Time 4/12/2019 11:41am
Paw Paw 271 wrote:
This lean condition spoke of can be from dirty jets in a carb, dirty fuel injector, incorrect TPS set too lean, but the one thing that...
This lean condition spoke of can be from dirty jets in a carb, dirty fuel injector, incorrect TPS set too lean, but the one thing that I see most is a bad exhaust gasket where the pipe mounts to the head. Most of these are a crush style gasket that folks want to reuse after the pipe has been removed, but in fact will leak when reused and cause this issue. If left uncorrected it can do harm.

Paw Paw
I also have some bad decel pop on my 18 KX250F but I read it's "normal" due to a bad map from the factory (?)
Is there a an hour mark to replace this gasket? Didn't find it in the maintenance chart.
Paw Paw 271
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Paw Paw 271 4/12/2019 7:15pm
4/12/2019 7:15pm
That gasket is bad if the exhaust has ever been removed.
You can help the bad pop even with a poor map if you increase the closed TPS setting.

Paw Paw
Titan777
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Titan777 4/13/2019 12:52pm
4/13/2019 12:52pm
Paw Paw 271 wrote:
That gasket is bad if the exhaust has ever been removed. You can help the bad pop even with a poor map if you increase the...
That gasket is bad if the exhaust has ever been removed.
You can help the bad pop even with a poor map if you increase the closed TPS setting.

Paw Paw
Thanks.
What do you think about cutting the right side of the airbox?
Can it cause any issues with the power curve? Will the bike just be louder?
Paw Paw 271
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Paw Paw 271 4/13/2019 2:27pm
4/13/2019 2:27pm
You can cut holes with no issue, but to remove more may upset the air flow.

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Freddyfred
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Freddyfred 4/14/2019 7:48am
4/14/2019 7:48am
Paw Paw 271 wrote:
Are we now talking about a 2 stroke?
What bike?
More info needed.

Paw Paw
Oops, yeah this is a 2-stroke. It’s a 2018 TM 300 MX with a Keihin pwk 38 carb.
mx900
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mx900 4/15/2019 5:56am
4/15/2019 5:56am
I had a 2008 Suzuki RMZ 450 mater of fact I still have it and it suffered from horrible decel pop. I have many friends that are outstanding mechanics and we chased everything we could to figure it out. I was running a DR D pipe and had it on the bike for a while. I came across a deal on a Yosh pipe and went ahead and installed it. Not because I thought the DR D was a bad product but because I had got a deal from Yosh on my newer RMZ for pipes and just wanted it to match. Once the pipe was installed the pop was gone! So Im guessing somehow there was a air leak in the old system. Like I said I still have the bike and no longer have the issue.
GingerVision87 4/17/2019 3:02pm
4/17/2019 3:02pm
I have removed literally hundreds of pipes and never replaced the crush header gasket..ooops. Never had decel popping though. Did you put a new pipe on without a re-map?

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