My bet is something much easier to fix. How old is the gas you are running? I have fired engines that ran fine when last driven and then after sitting for a year and the gas will varnish up the valve stems and bend pushrods after a few minutes running.
Is it predominantly the intakes that are bending?
I have dumped the gas and then run a couple gallons of 2-cycle mix and then new gas and the problem clears up.
Dry valve guides? Dry enough to bend push rods? Never been here.
I've seen a few reports of that over on The HAMB.
The ones I recall had dry or nearly dry tanks, where the fresh fuel dissolved the old varnish and deposits in the tank, and they redeposit on the valve stems (elsewhere too I'm sure, but it doesn't seem to cause the acute problems except where it can cause something to lock up).
