Popping on Deceleration - Honda Rebel Forum
 
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post #1 of 10 Old 03-01-2019, 07:19 AM Thread Starter
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Popping on Deceleration

Hi All,


Been about 600 miles since a carb rebuild on my 02 Rebel 250 and it runs beautifully. Had it out yesterday and noticed a popping sound (1-2 pops) from the exhaust as the engine decelerated from 7K to 5K. No hesitation or other issues with the engine.


I pulled the plugs to see what they look like and check for any indications of an unhappy mixture. Looks good to me, but thought I'd get your opinion. Thanks!




Cary
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post #2 of 10 Old 03-01-2019, 08:26 AM
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plugs look good - is your enricher all the way off ?

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post #3 of 10 Old 03-01-2019, 10:13 AM
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What did you initially set the air/fuel screw to? Try turning it out some. Plugs look OK, but are on the lean side, and popping is usually a sign of a lean condition.

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post #4 of 10 Old 03-01-2019, 10:44 AM Thread Starter
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Thanks for the quick replies. Yes, enricher verified to be closed. I do wonder if it is running a bit lean, as the popping only started in cooler temps. Perhaps the change in air density allowed the condition to reveal itself. Again, though, it has no hesitation on acceleration and runs happily along at 85 mph with full throttle.



Maybe try a quarter turn richer.
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post #5 of 10 Old 03-07-2019, 08:13 PM
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After a carb cleaning mine popped a little when hot and decelerating. My assumption was it was too rich. BUT comments on the forum said NO - it was too lean. Just seemed wrong to me but I took the advice and richened with the idle mixture just a little. It went away. Problem solved.
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post #6 of 10 Old 03-07-2019, 10:03 PM Thread Starter
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Yes, I adjusted the mixture 1/8 turn richer and the problem seems to be gone. Thanks!
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post #7 of 10 Old 03-11-2019, 07:30 AM
 
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Exhaust popping comes from incomplete combustion in the cylinder, so that unburnt fuel ignites in the exhaust system when it meets air.

You need a tachometer to set the idle mix on a warm bike, to find that point of just max rpm.

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post #8 of 10 Old 03-12-2019, 12:47 AM
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Quote:
unburnt fuel ignites in the exhaust system when it meets air.
That was my understanding too so my first attempt at a solution was to "lean" the mixture screw but that did not help. Making it "richer" seemed totally counterproductive but to my surprise, it fixed the problem. Can anyone explain why?
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post #9 of 10 Old 03-12-2019, 01:05 AM
 
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@raymacke this may explain it
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post #10 of 10 Old 03-12-2019, 08:18 PM
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EXCELLENT! Thanks for the link. It explains what is happening and why richening the mixture helps solve it.
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