Mower dies when engaging blades

[TiIngot]

This is a Scotts by John Deere.

Things done and checked:
1. PTO: pulled pto off my other mower and switched out. Same behavior using known working pto at full throttle.
2. Compression check: one cylinder at 138 lbs and the other at 130lbs.
3. Spark: Pulled each spark plug wire while running. Strong spark on both observed jumping from wire to engine body.
4. Deck: pulled belt off pto. Engaged pto running the motor. Pto engages fine. Put belt back on pto. Engage pto at full throttle. Motor dies.
5. Hook yard trailer filled with dirt to mower. Drive it all over the yard, including inclines. Pulls like my other mower.

I’m totally stumped. It’s like something binds that I cannot detect using inspection techniques.

Sounds like my Briggs V Twin problem. Tractor came to me not running. With new battery and wiring issues fixed it ran what I thought was ok but then, no power when PTO engaged, it died. Found mine was running on one cylinder. Getting spark. Getting fuel. Compression great. I had two problems, and it was the chicken or the egg. Do not know which happened first but I think the mouse started it all.

When running, feel the heat of both rocker arm covers. On mine, one was much hotter than the other. The cooler cylinder was not working because both my valves were always closed. That cylinder had good spark, fuel and great compression. But, removing the rocker cover from the cooler cylinder found both pushrods bent, broken and the valves were not operating at all, always closed. The valve guides were extended/pushed out of the cylinder head causing the valves to not travel the proper distance which bent/broke the push rods. OVERHEATED.

Excessive heat caused the valve guides to slip out. The cylinder head cooling fins were completely caked with mouse nests. I mean bad!! No air flow. The second issue I had was the flywheel key was found sheared, slipping the fly wheel 1/8" throwing the timing off causing excessive lean/hot mixture. And I do mean hot. After replacing the cylinder head and starting the engine the exhaust on the once cold cylinder glowed red hot catching an oil rag under the rocker cover on fire. That is when I found the sheared key too.

Removed mouse nests, a $2.13 key and $260 combined for new cylinder head w valves, two pushrods and gaskets later, then adjusting the valves it is running as new.