12.5 hp briggs and stratton flathead and i turn the key over and the motor spins but doesn't want to start

Its a 12.5 hp briggs and stratton flathead and i turn the key over and the motor spins but doesn't want to start. ive tried doing everything using the choke and starting fluid, but it won't idle by itself, i have no idea why please help.

Spark, Compression & fuel. That's what your engine needs to run.


You say it won't idle by itself... does that mean it will run on starting fluid? If so you've likely got a fuel issue.
If the fuel itself is good it's probably time to clean the carb

what he said.

is it getting fuel? Does it have good spark? It could be a dirty carb

Safety switches in the mower? are they bad. killswitch not bad and grounding the motor off? Just some ideas.

Killswitch wire*

If it runs on starter fluid, but not without it, then the carb is dirty/plugged, or it may be bad gas

Didn't see that clearly

see if air is coming out of the carb. i just had the same problem.

I don't even remember posting this, but I found out that the spark plug had stuff on it. I put it in the wire wheel, slapped it back in, and the motor fired on gas, smoked for a couple seconds, but it started and ran fine, still does to this day.