Still backfiring

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Still backfiring

Postby oregszun » Thu Jan 11, 2018 3:55 am

Hello Everyone,

I am an owner of '92 Helix, living in Hungary.

I have bought and installed new carburetor, intake manifold and muffler (from helixparts). Checked the system for air/vacuum leaks, adjusted the valve clearances.

Despite that I still have severe backfire, and mileage is also low a bit, I think (bellow 50).

Do you have other idea, what can cause the issue, what to check?

Thanks!
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Re: Still backfiring

Postby birdmannn101 » Thu Jan 11, 2018 6:11 am

Another thing that can cause backfiring when you have the throttle revved up and you quickly bring it back to idle. That is the top cable on your carb has slack in it and needs to be tightened up at the carb.
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Re: Still backfiring ANSWER

Postby zozman » Thu Jan 11, 2018 7:17 am

oregszun wrote:Do you have other idea, what can cause the issue, what to check?


Backfiring on decel is a result of an over lean firing condition.

1. Fatten the carburetor jets to 115 slow, 38 or 40 main.
2. Check the air cut valve on the back of the carburetor that it holds vacuum. Replace if necessary.
3. Check the muffler exhaust gaskets are not leaking.

Note: If you replaced the original Keihin carburetor with a off-brand, it may have lean emissions-friendly jets.

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87 & 98 Helix
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Re: Still backfiring

Postby Dale Gribble » Wed Jan 24, 2018 12:30 am

birdmannn101 wrote:Another thing that can cause backfiring when you have the throttle revved up and you quickly bring it back to idle. That is the top cable on your carb has slack in it and needs to be tightened up at the carb.

Can you explain a bit more?
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Re: Still backfiring

Postby birdmannn101 » Thu Jan 25, 2018 3:08 am

Dale Gribble wrote:
birdmannn101 wrote:Another thing that can cause backfiring when you have the throttle revved up and you quickly bring it back to idle. That is the top cable on your carb has slack in it and needs to be tightened up at the carb.

Can you explain a bit more?


Sure, I replaced the carb after cleaning the jets and just "half-assed" put the throttle cables back on the carb. Rode it around and noticed a "muffled" backfire every time I released the throttle. Well, I knew it wasn't coming from the exhaust gasket, nor the carb insulator because I didn't hear this muffled backfire earlier when I was riding around so somewhere in the service manual I noticed to "adjust the throttle linkage" and I noticed the throttle cable was slack at the carb so I tightened it up and it stopped backfiring.
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