MASSIVE backfire issue; I have tried everything with no luck

jake7022

New Member
Oct 10, 2021
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Lately I bought a generic 80cc 2 stroke kit for my bike, but have been suffering issues with backfiring when braking or slowing down. I have checked connections, tinkered with the fuel mix, I even opened the cylinder and cleaned carbon off the piston (it had been running rich for a while before that). Nothing has seemed to improve it, it backfires whether its running lean, rich or just right.
I don't know what to do now, maybe get a new cdi and a spark plug? After that I have no idea.
 

jake7022

New Member
Oct 10, 2021
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Its running lean. Check for air leaks.

When I first realized this was a problem I pulled the plug and it was completely black. It isn't running lean, I'm sure of that. I have it running at the right ratio now, and the problem persists
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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Los Angeles, CA.
I concur with wheelbender6... back firing is a lean condition... The fact that it happens when slowing down is because when the carb is closed, the heavy vacuum just behind the closed carb is drawing in air from a leak somewhere!