UPDATE!!! I have just been in touch with the Greenfield Technical Department. In the past, they would only help their dealers, but this time they have been most accommodating. According to their records, the machines rolled of the production line with 1/2 x 5/16 chain and top sprocket. I can only assume that they also had the 3/16 sprocket on the axle as well. I've always thought the engineering principles behind this brand were a bit sus....and now I have the proof. Thanks Grumpy and Aldot for your replies. I'll stick #40 chain back on and cross my fingers.

You can be part of the problem.....or part of the solution.
IT'S YOUR CHOICE...EVERY TIME!