gx345 looses power, throws pushrod

[hhsco]

My folks have a gx345 with ~200 hrs on it. Nice cutting machine but something always seems to be "up" with it in the last few seasons.

The current issue is that after starting up quite nicely and cutting grass for 20 minutes to an hour, it loses a cylinder. Got spark, fuel, etc. Checked compression and had zero on the LH cylinder so opened up the valve cover and the top pushrod fell out into my hand. Popped it back in place, ran great for 20 minutes, then the pushrod popped out again. Adjust the rocker arm set screws a little and it ran great for an hour and then threw it again.

Is there an underlying problem here that could be causing this issue (head gasket, scarred cylinder, messed up valves?). The pushrod appears to be perfectly straight. There is nothing particularly interesting happening when I lose the cylinder- it's not bumpy or mowing hard or anything like that- just normal mowing.

Thanks for any input- I'm more familiar with 2-cycle snowmobile engines that lawn mowers but I can muddle around with the right guidance.

 

[Yellowfever440]

Compare then push rod guides that are pressed into the head. The water pump may have went out and the head is heating up and those guides move and it holds the valve open just a little. So the pushrod is real loose and falls out. If that's the problem look over your water pump and replace the head.