What replacement belt do I need for Briggs Stratton 650 self propelled

unbolt top cover 5/16, unbolt bottom cover 3/8 unbolt blade 9/16 or 5/8 remove old belt, install new one, install covers and blade

disconnect the spark plug turn the mower on its side and inspect the drive belt on the pulley above the blade (on the crankshaft) it may have a shroud over it. Also there is a small gear case that maybe dry that the belt drives, that goes to the wheels, Also try lifting the drive wheels up off the ground and engage them and see if it still does it. if it stops once lifted it might be the bushings on the axle its self.

Should be a drain plug on the bottom of the motor remove it drain the oil replace and refill

Any good grade of SAE 30 will do fine unless on cold weather operation..then SAE 10-30 ..

Different motors use different plugs. This chart will help you find what you need.

https://www.jackssmallengines.com/Products/BRIGGS-STRATTON/Spark-Plug

use 10W-30 or for best performance, use synthetic 5W-30

if cable is all intact, just hook it back up, if broken, then replace it.

I don't have this kind of mower. But I was faced with the same problem recently. I got my belt back on by taking a large wrench and affixing it to the bolt head holding the pulley which you want to slip the belt on. Hold the belt firmly against the pulley and turn the wrench and the belt in the grove will walk around the pulley until it slips in place.

check the fly wheel and coil it may have rust on it if so sand it off

when the lawn mower suddenly stop working,first you should check the fuel. i think the Self-propelled device was broken. You can take the Self-propelled device off and try again with it.