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Was running fine. Now one cylinder is running real rough (with backfires) and exhaust has raw gas smell. Air filter is clean, gas is fresh, carb linkage is free and lubricated
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Previous owner had way overfilled crankcase oil. Oil had gotten into carb and clogged air filter. Drained oil to correct level. Ran engine but kept cutting off-see above. Took off carb cover cleaned housing and ran without air filter-ran fine. Unsuccessfully tried to clean air filter with gas-did not work. Apparently, the engine could run just long enough to exhaust the air in the old filter and cut off which is why it would start back up after a few seconds. Bought new air filter-whole thing-about $15 at Carquest. Put in some carb cleaner and installed the new filter and it runs perfectly.
When it runs rough is it blowing dark smoke? This is a sign of running rich like a choke will do and can cause stalling especially when the motor is warmed up. If it is not blowing dark smoke it sounds like maybe your injectors are not working properly and it is not getting enough fuel through them under load. either way as an injected machine it sounds like injectors may be the culprit since youve taken care of some other issues. You might try running a heavy dose of an injector cleaner through it (I've had good results with lucas brand) and see if that helps. Otherwise, you might try to manually clean the injectors.
Backfiring out of the exhaust is usually an ignition problem. Unburned fuel is getting into the exhaust system because it's not being ignited in the cylinder. When the engine fires on that cylinder again, it ignites the raw fuel in the exhaust causing the pop that people call a backfire. I'd investigate the ignition system. Connect a timing light to each of the spark plug wires if it has a single fire ignition or either of them if the ignition system is the stock dual fire. Start the engine and watch the timing light to tell if the engine is missing as the light will miss a flash.
Sounds like the carb has not been cleaned properly, gas overflow like that could be caused from a worn seat/needle. Did you put after market exhaust on it?
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