NormK all appears well after several minutes revving it at different levels and stopping and restarting it a few times. Lucky there was a strong breeze to carry the smoke away down the street. Exhaust is fine now.
Thanks for the pointer.
PS: discovered another minor issue. As the engine winds down to a near stop, as you shut it down, the piston "bounces" and the flywheel feels like it goes the other way for aa split second before stopping completely. When I did it again, it winds down and stalls abruptly instead of spinning freely to a complete stop. Weird.
Last edited by Mowerfreak; 19/09/18 07:56 PM. Reason: Forgot another point.