Old Briggs made Toro Engine runs too fast

[Cfs]

I have a Toro super recycler that is from 1999-ish. It’s a Toro model # 20040 SR-210S serial # 9902466.. I have looked up the mower on Toro’s site and it is not identified with a Briggs model # and is referred to as a model GTS200. That said it appears to have been made by Briggs and is an overhead valve 6.5 hp engine.
I have two issues I need help with. 1. The engine seems to run at too high of a RPM. There are no adjustment screws on the carb. The engine has a primer for starting not a choke model of carb. Not sure what I should try to do to make it run slower. I have had the carb off and cleaned it. I did notice that the throttle butterfly seems loose almost to the point of being sloppy. Not sure is a worn throttle shaft could cause the runaway speed issue.
2. The mower starts fairly easily when cold, but a warm/hot restart is very difficult. It seems to give a little bit of a backfire sort of pop when trying to warm restart. I adjusted the valve lash on both the intake and the exhaust to .005 and it doesn’t seem to have solved the problem. It has a new spark plug and aside from the hot restart issue, it seems to run great, doesn’t smoke or miss when running.

Any and all comments and insights are greatly appreciated

 

[Auto Doc's]

Hello C.,

These engines run at a fixed high RPM of about 3400 RPM as I recall. They do not have a throttle cable to regulate the engine speed like the older mowers did.

You might try hitting the primer bulb just once when hot to see if that helps.

Otherwise, the primer bulb and the air cleaner backing gasket likely need to be replaced.

Make sure you keep the oil full and changed if needed, because dirty carbon black oil can contribute to this problem.