M20 Backfire at startup
 

I ran my 2072 today around the yard. ran fine. I shut it down for about 20 minutes then when I started it back up It backfired when it started. Now every time I start it when it's warm, It backfires 1 time and then runs. It runs fine but smells like it's running rich.

Check the oil and make sure the fuel pump and/or carb hasn't filled the crankcase with gas.

I just changed the oil today. It didn't smell of fuel at all. I think I may just have it running to rich.

I leaned it out and it seems to have stopped backfiring when it starts. I think I hear a bit of valve noise. Maybe i'll adjust the valves again.

You 'adjust' the valves on an M20 by grinding the stems. If they are within spec, leave them alone. These engines have valve noise, and it's nothing to worry about.

Push the throttle down to idle when starting.

That should cure the problem.:bigthink:

Thanks Matt I'll leave it alone. It isn't doing it since I messed with the carb so hopefully it stays that way. I'll keep an eye on the oil though just to be sure it isn't filling the crank case with gas.