Export thread

My son started the lawn tractor mower and a minute later it shut of on him. he said it sounded like he hit something. I took the engine cover off and pulled the plug. I can manually turn the flywheel about 1/2 turn before he locks up. I can turn it back the other direction same 1/2 turn and it locks up. I obviously know something broke but just trying to find out if anyone can tell what let go from this description. I checked the oil and it is a little low but not empty. I'm trying to decide if I should look for a used motor or undertake fixing this one. thanks

It could be a bent conrod, a broken Counterweight con rod or something under the flywheel.

Easy bit first is to pull the flywheel off and look for something stick in the stator or a magnet fallen off.

After that it is going to be engine out & apart job.

Before you pull the engine, remove the belts from the engine, just in case something is stuck underneath.

A bad valve hitting the piston?

Thats what I was thinking. I'm going to have to take it down to confirm and check the damage

I've seen the overhead valve Briggs drop a push rod and hit the crank and do what you're describing.