Murray riding mower Starter turning slowly

Model # 42576X92B 42" cut 2000 model. Brighs and stratton 16.5 hp OHV high performance I/C engine model # 313777 type 0134-E1. The mower cranked and ran 3 days ago, although it turned slowly when cranking. The battery is new. I tried jumping it off with the car but it still turned slowly. Also tried jumping it with cables connected directly to starter and frame with same results. Tried cranking with the plug out and it spins fine then. The flywheel turns freely. I know about the compression valve, but would it have cranked 3 days ago if this was the problem? I need to avoid any unnecessary repairs or parts due to a limited budget. Any help would be appreciated.

 

You probably need to adjust the valve clearances. That would account for what you're seeing. Usually you would have a tough spot on the engine rotation at top compression where the engine would hang a little.

Problems solved by setting the valve lash comes up here quite often.

 

Agreed, adjust the valves. It's a recommended yearly service procedure... I'm betting it has never been done.

 

Thanks guys. I was hoping for another solution, but I thought this might be the problem. My mechanical skills are rudimentary at best, but I did find an in-depth tutorial online. I just didn't understand why it cranked one day and not the next. I know it hasn't been adjusted in the 10 years I've owned the mower. Hopefully I can pull it off. From what I have read the adjustment can be tricky. Thanks again. This is a great forum.