Murray 20" with Tecumseh 5.0 HP engine

[herd799]

I have a mower that my father-in-law gave me that was running great until one day it would not start. When you pull the cord to start it, it feels like the recoil is stuck. I pulled off the recoil, and it moves fine. When spinning the engine by hand, it is stiff and hard to turn part way through the stroke. I pulled the head off and the piston seems to be moving fine...in fact it moves great with the head off.

I am not an engine guy but I am trying to learn. Can anyone help me diagnose this?

Thanks!

 

[ILENGINE]

Carbon buildup on the top of the piston and the head. Reduces clearance and will feel like a tight spot. I have an uncle with a generac generator that builds up carbon and then flakes loose and appears to lock up the engine at top dead center. Sometimes we can roll engine back and forth and break it up, some times we have to remove the head and clean it out manually.