Jun 3, 2019
amusall said:
What about going the other way, switching from methanol to gas? I went with the #37 jet as the only change. Engine starts but is tricky to keep running and falls on its face when opening the throttle
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What kind of carb are we talking about? The original Briggs carb?
If so, then you're close on the jet at .037." I generally suggest .038."
The needle is used to tune a flathead on gas moreso than you would with alcohol. Start @ 1 1/2 turns and adjust from there.
If it idles fine, then falls on it's face when you step on the throttle, then it's likely too lean.
You may also have something plugged up in the carb (small idle circuit, pick-up tube, etc.)
If you've loosened the flywheel to change the ignition timing, then make sure that it is torqued plenty tight -- they slip easily if the taper is not lapped properly.
Also, check your plug gap -- Most WKA/IKF flatheads will use a slapper cam that "lofts" the valves. The intake valve will tag the ground strap on the spark plug if it is not indexed correctly, and that will make the engine fall on it's face when applying the throttle from an idle as well.
The big hole will be .059 -.062 in size . on a race /alcohol carb .
all you should need is a diaphragm and jet maybe a new needle . and the tank gasket .
timing will be advanced on methanol Roughly 4 * , I would do carb first and go from there.