Difference between Hough H50D H50C/B etc.

I talked to Bob at Contenental Equipment of Dallas and he said that there were only H50, H50B, and H50C like the manuals listed on the sight. The Serial number listed for my unit is 17AH-1047, which corresponds to a H50. The H50 includes serial numbers 17AH-1001 to 1600 and so the H50D must have been due to this being a military contract unit or something.

By the way, I traded my old Ford 8n with an old light disk and 4' mower for the Hough. The 8n had a bad engine but ran ok. I had about $1,500 in the equipment I traded.

The H50D runs ok once started, but I have to use ether to keep it going for a while. I try to limit the ether to just what is necessary to keep it going. A friend suggested that I try to use WD40 to stert it or keep it going to minimize the chances of ether damage. The unit has a rubber push button and glow plug guage mounted under the dash, but the guage never read anything. When I push the button, I hear the solenoid activate, and when I let up I hear it disengage. If I then push the button again, it doesn't do anything. Are there any wiring diagrams or testing methods for this circuit? Would they be in one of the service manuals on the YTMag site?

Thanks for your help,
John