Have a 19.5 briggs single piston on zero turn. Starter got to where it would not spin motor. Changed battery, and starter (twice). Still locks up on compression stroke.

I was told these new briggs has a decompression lobe on the cam. But I bought a manual and it does not say anything about that. I took the valve cover and drilled a small hole over the exhaust valve. I can stick a small screw driver and hold the valve down just a little. I have to hold it open till the engine starts trying to fir when I release the valve the engine will start and run fine till I kill it then have to depress the valve to start it.

Doe anyone know if there is a decompression valve on it and where it is located.

Thanks.