Help with 1968 Cub Cadet 125

[jet62095]

Hello,
I have a 1968 Cub Cadet 125. I'm trying to use it as a snowblower tractor. It has low compression, I removed the head and there are no visible signs of damage. I try to start it and it backfires out of the carburetor. Once started it will run just fine. If I put load on it, it will squeal and white smoke will come out of the breather cover and the motor will eventually overheat and shut off. I originally thought this was oil burning, but I have replaced the oil with synthetic, which would greatly reduce burning, but it has made no difference. The oil remains clean the entire time. I am starting to think it is a bad piston, but have heard that it may also be a bad head gasket or exhaust valve. Please help!
Thanks!
John

 

[temarthers]

Backfires thru carb or air filter: Intake valve not seating properly, check lash and/or reface valve & seat.
As you can see from the Signatue, I have a Cub 125 as well. Dad bought it when I was 7 yo, now 51,
still runs and cuts grass, rear tires original, deck and everything else also, only thing changed was New seat, and
new front tires, other than that, All original