Briggs and Stratton engine will not turn over using starter motor.

[blackbuttdisco]

I have a 4 year old John Deere (JD) ride on mower with a Briggs and Stratton engine. A month ago it refused to turn over so I suspected the battery. Had it checked and ended up buying a new one. No change, still turned a bit then came to a suddden stop. I could turn it over by hand so it appears there is nothing physically stopping it from rotating. Next I bought a reconditioned starter motor from JD. No improvement. JD suggested I check the valve clearances, I did and re set them to 4thou as they said. Still no change. I undid all the wiring connections, cleaned and refitted them, still no change. I can usually get any engine going but this one is getting to the point where I will have to take it the 100km to JD. So does anyone have any ideas? :(:mad:

[bee utey]

Flywheel slightly loose? If the flywheel tilts under starter load it will lock up.

[Tote]

Briggs and stratton engines have a lobe on the camshaft that acts as a decompressor at low speed. If the tappets are out of adjustment the lobe won't lift the valve and compression is too high for the starter motor. I'd check the tappet clearance.

Regards,
Tote

[DeanoH]

Have you checked the voltage at the starter motor solenoid ? can you hear it pulling in ? If you can hear it going 'click, click', check the battery and starter motor cable connections.

You will find that the starter motor circuit will be wired through various interlocks (for safety reasons). For example, the starter won't turn if the switch that turns on the drive to the blades is on. On mine the switch contacts that allowed the starter motor solenoid to get power were crook. I could 'jump start' the mower but not start it with the key.

Deano :)

[Tank]

If you haven't used it for a while you probably have a valve rusted open, esp. if it is a Side Valve, if it is OHV take off the rocker cover and disconnect the spark plug wire and rotate the engine and watch the valves, if one is stuck open then it has probably whacked the top of the piston, bit of WD40 and try again, regards Frank.

[roversmith]

Later model briggs and stratton have a centrifugal decompressor built into the camshaft, this has a habit of self destructing. check it, will punch a hole in crankcase if it gets between the balance weight and case. symtoms are hard to crank over.