I finally found my service manual. (90-43183)
Setting the float level is indeed odd: The trick is, you hold the carb upside down and hold the float so that it just touches the float pin. You don’t let it collapse the float pin. While holding just touching, the height from the bowl flange to the bottom of the round float should be 7/8″ to 31/32″.
Although the manual shows the choke assembly disassembled, it does not have specific wording on how to do it. #27 is a “rubber cap” and under that, is #26, the retaining clip. Prying off the rubber cap seems a safe bet.
I have no info on fuel ratio but I bet it was 50:1. I’d be real happy and confident with 24:1.
There weren’t many of them around in my area. Those like yours are technically not “Gnats,” which were named so only the first year and were TWO cylinder, 4 hp. They pretty much stunk (The Mercury tech rep called them “f—ing Guh-Nants.” but they are cool, in that the real Gnats were the last Fond Du Lac produced, American portable motors. When they started with the Mikuni carbs and everything else, it started getting vague about their origin. Be very diligent about the gear oil. They did tend to lunch gears if they lost any of the small amount of gear oil they had. I would check it after every use; but that’s just me.
Long live American manufacturing!
