Ok Guys. Cranked her up this afternoon, all was normal on idle warm up.
Had the tiller attached. Lifted it up a little to drain and change oil. Boosted the RPM a little to do so as it is heavy and the pump would keep the tiller up. It drops an inch or 2 and system would lift. Normal thus far with all implements.
This took 10 min or so and when complete I looked up and tractor was blowing black smoke...I mean blowing it!
I moved tractor over to garage, smoke increased with rpm rise. Parked...dropped throttle lever back down to shut down...but the rpm stayed high! The only way to shut down was to shut fuel off.
Restarted hour later after cleaning air filter etc...and piddling otherwise and same thing....smoke. no power loss it seemed.
I will say this time I did not shut fuel off. I pulled lever back to shut down as normal and though the rpm stayed high it Slowly petered down and shut down on own.
So, what have out on me?