How to slow down speed of self propelled 6.75 hp briggs/stratton lawn mower engine

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

Your mower doesn't have enough power to handle very thick grass at high speed. You need to go slower across the lawn. That's easy to do if this is a push mower (just don't walk so fast) or if it's a self-propelled model with a speed control. But if it's a single-speed model you'll have to mow the lawn in fits and starts: squeeze the lever to move it forward; release it when you hear it bogging down; wait for the motor to reach full speed; squeeze the lever to move it forward again; repeat. Also, is the grass very high? If so, try setting the cutting height higher on the first pass, then lower it for a second pass. Finally, make sure the blade is sharp.

remove the top cover from the engine and see if theres a nest stopping the governor from moving

valves bad need valve job

Is the choke stuck on? That could do it. Does it rev high enough ? May need adjusting. You say you added oil was it low enough you have almost seized the engine. Just a thought

Are you running it with the choke on? Also if the air filter is dirty it will do that as well. Black plugs means it's getting too much gas and is not getting the proper air to burn properly. Some engines if you rev them up with the handle right as fast as it will go automatically the choke is on.

http://www.briggsandstratton.com/maint_repair/manual_and_more/

Save this is your computer. Lots of info here.

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.