I have a Tecumseh 6.0 powersport engine that runs rich at wide open throttle. The carb is clean, new sparkplug, fresh gas. The plug is covered with soot. It will go flat on top end then will not idle. Its has a manual choke carb. Any help would be appreciated.

Tell us more - if Tecumseh put a carb. on there, it probably isn't a normal production one. They used Tillotson on their larger Motorsports engines, and often didn't supply one. What make and model of carb. is it?

I'm wondering - almost sounds like restricted exhaust what with the symptoms you provide.

It has a Tecumseh 640346 carb, I had someone else tell to check the valve lash. I looked up the spec in the manual, and under valve clearance it states .004, I've heard that it should be .004 to .006 on intake and .006 to .009 on exhaust. What do you think. I checked the exhaust for restrictions and it's fine.

Check the float Level, it should be parallel with the carb when you hold the carb upside down. How can you tell its running rich in the rirst place? what are the symptoms?

The plug is covered with soot, you can see black smoke out of the exhaust. Even at wot it loads up and slows down.

Is it possible the engine backfired and partially sheared the flywheel key, which would change the timing. Have a good one. Geo

The float is level with the carb. It has a new needle and seat. Is .004 lash on both valves correct?