Small Engine Troubleshooting Problems? Ask a Mechanic Now.
This is caused by fuel dripping fuel after you try and shut it down which causes backfire.
You can try adding some sea foam to fuel and run a few tanks of the mix through it that contains seafoam/gfuel mix and it usually clears up.
If it does not clear up the obstruction is to great inside the carburetor and it will need to be replaced or rebuilt.
The other cause could be valves out of adjustment but I would try seafoam first.
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