by KE4AVB » Sun Jun 02, 2019 12:05 pm
Depends...Is this the actual after fire problem out of the exhaust or is it out of the carburetor?
The after fire (often called a backfire) is raw fuel entering the hot exhaust and the after fire solenoid was added to carburetors to help prevent this. The raw fuel ignites in the exhaust due it being red hot internally.
The real backfire out of the carburetor can be caused by ignition timing usually. Something like partially sheared flywheel key. I ran one case where I had a 310000 series randomly sneezing out the carburetor. Not something that shot a flame out of the carburetor. This was an intake manifold air leak. On a Homelite I had a coil that did it so bad it was setting the air filter on fire.
I had Kawasaki engine igniters to misfire on at the top of the power stroke and then ignite the fuel on the exhaust stroke. One of the drawbacks of the wasted spark ignition system. A failing plug may fire under compression but fire fire on the exhaust stroke. The first one I came across I nearly wet my clothes as it was as loud as a 12 ga going out right beside me and that was with the muffler on the engine. It also shot out a twelve inch plus flame everytime it did it. I was nervous wreck the rest of the day.
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