Briggs 12.5 I/C non OHV turns over slow and stops on compression stroke.

[mbelus]

You need a different battery. Need more cold cranking amps.

 

[jreiber83]

Or starter is going out. Easy to rebuild and fsirly cheap but would start with new battery.

 

[scottmoreland]

well their isnt that much too it , you said you had the head off, did it have carbon on piston top and or cyl. head , I just had a 2 cyl. 18 hp that cranked hard also and what I did was finally sprayed water mist thru carb while on high idle to clean off piston and combustion chamber. or you might have too much timing advance, which I was told once if you set the coil gap from .030 to about .060 it would retard the timing maybe 2 to 3 degrees. ,, just food for thought. I you voltage dropped and non over 1 volt while cranking and starter is new I think you stated ..that should be it . unless the top of cyl. bore is scored but that you would of seen with head off.. let me know.

I had the same problem with my 18 hr brigs twin cyl . It ended up being battery cables . Installed new cables and i think that the ground was bad to . Works like a new one now.

 

[hsherm]

I just now read through this posting. I don't want to sound insulting, but I didn't notice if you had said anything about checking the oil level or not. Too much oil will cause this same problem. It's a simple thing to overlook, but it happens.