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Cub Cadet - Backfire problem.
I have a cub Cadet model 2146 with a 14 HP Onan engine model ZX390 11317D. The engine runs fine except it backfires eight out of ten times when the key is turned off. This happens regardless of throttle RPM speed. There is also a 10 second spark knock prior to the backfire. What may be the problem or a solution?
Thanks to all.

let it idle and cool down before turning off the key

Is your carb equipped with an anti-backfire fuel solenoid? If so, it may have given up the ghost in the open position (unusual, but possible).

When was the top end last de-cocked?

Sorry, but I don't know what this means. Are you talking about timing?

"When was the top end last de-cocked?"

Thank you for the prompt response.

trickydickie said:

Sorry, but I don't know what this means. Are you talking about timing?

"When was the top end last de-cocked?"

Thank you for the prompt response.

Click to expand...

I'll guess he meant "de-coked", as in carbon removal. You might try a slug of Seafoam in there. Stand off to the side when you fire it back up!