Old Briggs made Toro Engine runs too fast

C

Cfs

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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
 
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.
 
Toro published 3150 as the ideal rpm on my 21" recycler #20055. The industry spec of 3000 - 3400 rpm is based on 19000 feet per minute at the blade tip. Trying to set it by ear does not work unless you do it every day. You can get a free app for your phone that will give rpm or use one of several tools. I tried both an app and a spring resonance rpm meter, and both gave the same. The rpm is set on many Briggs mowers by changing spring tension. Make sure the governor hasn't failed.

(blade length x 3.1416) \ (19000 x 12) = 3456 max RPM. Toro based it on longevity and cutting quality.
 
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Thank you all for your in insights. I gave already replaced the primer and the odd shaped gasket that the air filter box attaches to on the outside of the carburetor.
I was given this mower from a neighbor who said she picked it up on the side of the road to give to a friend who needed a mower. When she was unable to start it she decided to scrap her plan and asked me if I wanted it. When I first worked on it I found the primer was torn and there were some screws missing for the blower housing. It looked like someone had taken it apart and attempted to repair the engine. So maybe someone has misadjusted the governor?

I have an old wire type tachometer that I can attempt to use on engine. I have had it for years and honestly I haven't used it in years. I will have to review the instructions on using it. I think it was a model that Tecumseh used to recommend made by a German company?

It seems like I so rarely have an engine speed issue that I haven’t adjusted governors very often and I have always had a fear of incorrectly adjusting it and setting it too fast and damaging the engine. But I think it makes sense to attempt to adjust this one and see what I can do. I will advise as to what I find

Thanks to everyone

Spit
 
Hello C,

The tool you described is often referred to as a vibration/frequency tachometer by some folks like me. I've had mine for 40+ years. I never can recall the German name of it. It is a simple device that works very well for reading the RPM on small engines.


Basically, you dial the internal stainless wire in and out until the tip of it vibrates (the colored tip) to the widest point consistently.

I had to put a dab of red nail polish on the loop tip of the wire on mine so I could see it better, it had worn off from years of use. Originally the tip loop of the wire was coated yellow or white if I recall.

The service manual that was attached in an earlier reply should help you.
 
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