tecumseh motor won't idle

I have some small Tecumseh motors (3.5 and 5hp - 2 different carbs for the 5hp). I've cleaned the carbs.

Can't get any of them to idle. All of them will run nicely at full throttle.
When they get near idle, they sputter and rev up on the governor.
Turning the idle jet screw seems to make no difference.
What am I doing wrong (besides trying to make a Tecumseh run)?


Any Briggs I've tuned will idle down to a nice thump, thump, thump.

How is the gasket on the carb ?? if it leaks that could be the problem or maybe a head gasket. maybe the seat on the needle is bad. don't sound like a real big problem anyways they shouldn't idle for more than a few seconds anyway its not good for them!!

I guess I have always been lucky they always run great for me on my old sears tractors. the ariens always seem to be blown up when I find them but usually thats because people push down on the handles and the engine starves for oil! always try to keep them running as level as possible .. keep the RPMs up and the head clean. I also run sea foam in everything.

On closer inspection, it looks like the head gasket on the 5hp is leaking.

I'm trying to get one of the motors to idle - it will be used on a mini bike with a centrifugal clutch. Not looking to idle for extended periods but don't want the bike to run away.

Hoping to see if there was some secret to setting the carb to get it to idle.