Backfire, chortle, popping - Harley Davidson Forums: Harley Davidson Motorcycle Forum
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post #1 of 14 (permalink) Old 09-18-2009, 12:02 AM Thread Starter
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Backfire, chortle, popping

New rebuilt motor: compression backing off and starts popping, chortle and etc. Exhaust still stock with inserts removed. Still using crossovers. '01 heritage Didn't do it before rebuild.
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post #2 of 14 (permalink) Old 09-21-2009, 08:14 AM
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carbed or efi?
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post #3 of 14 (permalink) Old 09-23-2009, 05:03 PM
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If its carbureted, try richening the idle mixture a little at a time.
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post #4 of 14 (permalink) Old 10-06-2009, 01:54 AM Thread Starter
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carbed or efi?
efi, rebuilt motor
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post #5 of 14 (permalink) Old 10-06-2009, 01:55 AM Thread Starter
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efi, rebuilt motor
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post #6 of 14 (permalink) Old 10-06-2009, 01:56 AM Thread Starter
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If its carbureted, try richening the idle mixture a little at a time.
EFI, rebuilt motor, mapping the same
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post #7 of 14 (permalink) Old 10-06-2009, 07:40 AM
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Originally Posted by Harley5212001 View Post
New rebuilt motor: compression backing off and starts popping, chortle and etc. Exhaust still stock with inserts removed. Still using crossovers. '01 heritage Didn't do it before rebuild.
Not enough info from you ... can't diagnose from the symptoms you described .
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post #8 of 14 (permalink) Old 10-07-2009, 12:02 PM Thread Starter
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backfiring

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Not enough info from you ... can't diagnose from the symptoms you described .
Motor totally rebuilt. Runs great except when backing off throttle the exhaust starts compression backfiring, popping. Going down hill at 40 in third gear with no throttle. I've heard it could be air leak? and also a valve hanging up in guide? How do I check valve in guide? It is EFI, 2001 twin cam. New everything inside.
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post #9 of 14 (permalink) Old 10-07-2009, 01:47 PM
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Motor totally rebuilt. Runs great except when backing off throttle the exhaust starts compression backfiring, popping. Going down hill at 40 in third gear with no throttle.
Ahhhhh....new info. No...not a valve guide, rather you're running lean.

You need to richen the fuel mixture up, or check for an exhaust leak on the rear pipe, if that's the ONLY pipe that's doing it.

If you're running too lean, it can do the same thing, but it's generally on BOTH cylinders, not just the rear one. Just having ONE cylinder do it sounds as if it's as simple as locating an exhaust leak at the head, or ar the pipe/muffler union.

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post #10 of 14 (permalink) Old 10-07-2009, 04:06 PM
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not a valve guide/valve prob,ive heard guys say that for ever,a valve isnt going to "hang up in a guide",then free up,once a valve seezes in a guide,motors spining so fast,the damage is done,its stuck,bent valve.you could have a ex. leak or its too rich way on the bottom and dumping raw fuel into the pipe,when this happens on a efi bike(like with a power commander,you zero out the first column,same princible with a carb,check you air/idle,lean it out a bit
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