6800 runs good till real long grass then fouls left cyl..

[crapover]

Black ish smoke and bogging. If I throttle down a hare and go real slow its fine. Is there a carb adjustment screw?. New plugs and new air filter. Gap may be off. Went one step hotter on plugs and it helped a little bit. Running carb cleaner in this tank of fuel.  Plugs are very black dry carbon.

[rattosh51]

You might want to check the valve adjustments too. Look thru some of the older posts, as I remember someone giving the measurement of what it's supposed to be. Otherwise sounds like it may be getting too much gas? All leads back to the carb-may need a good cleaning, or float may be getting stuck.
Also make sure you're gas cap vent is clear.