20 inches isn't 20 inches
I meant to comment about this previously, but forgot. Thanks to Happycheapskate, I'm reminded about it again. I was inspecting the driven pulley (bike rim) attached to my rear wheel and had a tape measure nearby. I decided to measure the diameter of the pulley and learned that my assumption about the bike rim pulley was wrong.
What I thought was a 20 inch rim is actually 16 inches. It's the outside diameter of the bike tire that's 20 inches. So here I was, thinking I had a 20 inch rim with a drive ratio of about 13:1, when really, I'm at about 10.5:1 That's probably part of the reason I'm so far above off my original goal of 20 mph top speed. Other parts of the reason may be that the engine is running faster than 3600 rpm, and Happycheapskates comment about the 26" wheels.
I'm going to take his suggestion to measure actual distance of one or two rotations on the 26" wheels and see how it all comes out.
By the way, does ULGE stand for Utility, Lawn, Garden Equipment?