Popping Carburetor

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roger99a
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Popping Carburetor

Post by roger99a » Thu Jan 07, 2016 1:31 am

What are the possible causes for popping backfiring through the carburetor at low to mid range RPMs? Symptoms abate as the engine warms but never completely stop.
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Re: Popping Carburetor

Post by dneprlover » Thu Jan 07, 2016 5:20 am

From those symptoms, I would suggest lean mixture
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Re: Popping Carburetor

Post by LRP » Thu Jan 07, 2016 10:37 am

Check for a broken carburetor slide spring.
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Re: Popping Carburetor

Post by berger » Thu Jan 07, 2016 11:57 am

roger99a wrote:What are the possible causes for popping backfiring through the carburetor at low to mid range RPMs? Symptoms abate as the engine warms but never completely stop.
Do you know what jets you are running? Bone stock?
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Re: Popping Carburetor

Post by Msblu79 » Thu Jan 07, 2016 12:57 pm

You are running slightly lean on the low speed circut. Just turn the low speed fuel screw out (CCW) a half or a full turn and see if that takes care of it. Add more until it stops popping.
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Re: Popping Carburetor

Post by scottolds » Thu Jan 07, 2016 1:10 pm

Also check your compliance fittings
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Re: Popping Carburetor

Post by berger » Thu Jan 07, 2016 1:16 pm

Msblu79 wrote:You are running slightly lean on the low speed circut. Just turn the low speed fuel screw out (CCW) a half or a full turn and see if that takes care of it. Add more until it stops popping.
Ya, my second thought.... :thumbsup:
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Re: Popping Carburetor

Post by Wildhorse Cafe » Thu Jan 07, 2016 1:26 pm

Bigger Jets, Bigger Hammer. They all do that.
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Re: Popping Carburetor

Post by Lokiboy » Thu Jan 07, 2016 1:35 pm

All the suggestions are valid. My money is on the need to enrich the air/fuel screw by a 1/4 turn or so, and check to make sure you don't have a crack or bad fitting of your compliance fittings attachment to the carbs

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Re: Popping Carburetor

Post by URAL CT » Thu Jan 07, 2016 3:56 pm

Went through this carb popping exercises not too long ago. I did all the hard stuffs first, like taking carbs apart, cleaning, adjusting the carbs, cleaned the tank & petetcock, etc... nutin' helped. Finally while helping a friend modify his trailer to fit & haul his toys for a trip & during the "I don't need ur help right now". I started doing the easy stuffs inspected the nuts & bolts that involved holding the carbs to the heads, then checked the exhaust & whoa...nut holding the right exhaust pipe to head was loose & one missing causing an air leak. This was causing the popping. Tightened all the fasteners I can get to, just to make sure. Popping stopped & all is well! YMMV...just sayin'
Moral of the story...check the easy ones first. :mrgreen:
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Re: Popping Carburetor

Post by rivers » Thu Jan 07, 2016 4:43 pm

URAL CT wrote: Moral of the story...check the easy ones first. :mrgreen:
Amen on the easy/cheap stuff first. Sounds like a lean issue from poor tune/set up or air leak. Bad compliance fitting(s) on an 07 would not surprise me at all. Easy enough to check with some spray carb cleaner, starter fluid etc. Keep in mind you want to tune/adj the carbs on a hot up to running temp motor.
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Re: Popping Carburetor

Post by roger99a » Fri Jan 08, 2016 11:53 pm

Thanks guys!
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Re: Popping Carburetor

Post by roger99a » Mon Feb 08, 2016 12:10 am

Just an update, the idle jets were dirty and one of the carb flanges was so bad it fell apart.
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Re: Popping Carburetor

Post by S 854 » Mon Feb 08, 2016 11:28 am

roger99a wrote:Just an update, the idle jets were dirty and one of the carb flanges was so bad it fell apart.
That'll do it... :wink:
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Re: Popping Carburetor

Post by eastbloc » Mon Feb 08, 2016 11:37 am

Bad compliance fittings will do it to you every time. It might be environmental, but I always found they had to be replaced once a year on average.
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