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Discussion Starter #1
My '77 FL has started backfiring on startup. Just as you hit the button, it bangs once out the exhaust before is starts. I would ignore it, but having a shot gun sounding blast at 7 am doesn't endear me much to me neighbors. Anyone have any ideas why it does this? Thanks.
 

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I had a problem with my 72 XLCH doing the same thing a while back, 'cept I had to kick it. Traced it back to ignition issues. Replaced the condenser, checked the points and re-set the timing and all was good. Just my experience.
 

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Bugman said:
My '77 FL has started backfiring on startup. Just as you hit the button, it bangs once out the exhaust before is starts. I would ignore it, but having a shot gun sounding blast at 7 am doesn't endear me much to me neighbors. Anyone have any ideas why it does this? Thanks.
do you normally turn off your petcock when you park the bike? if your float is not holding, and if you have a dual fire setup, the cylinder on it's exhaust stroke and/or the exhaust pipe may have some raw fuel laying in it that's getting touched off by the first wasted spark.
 

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My 56 FLH does that once in a while. But it's kick start. On my bike it's a fuel issue. Usually happens late at nite when your trieing to sneak away from the bar.
 

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do you spin the throttle alot before you hit the button? sounds like "raw" fuel is re-igniting .... i.e flooded before starting, if this problem only happens on start up...

Also can be caused my nippers making alot of brum brum noises, and peeling the throttle, before ignition....

Just a thought. if it was "electrical" more likely to effect it while idling at the lights etc...
 

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Check the plugs and ignition system. If you have raw gas flowing past the float and into the barrels, you have more problems than backfiring - the gas will find its way past the rings and strip the lubrication off the skirts and the barrels - and can certainly get into the bottom end - VERY bad.
 

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Discussion Starter #7
Thanks for the info. I don't shut my petcock off, and I generally give it 2 pumps of gas and some choke to start it. I'll start paying attention to see if it's always the same pipe blowing off. If it is, Then I'd guess maybe an ignition issue.

Can how I shut the bike down be causing this?
 
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