Re: Johnson HD-20 Won’t start

[aquasonic]

I can tell you from experience that the high and low speed systems are very closely linked in this smallest of rotary valve motors. I have had a few frustrating times with trying to get mine started, only to find out that the low speed needle had backed out way past where it should have been. That caused a too rich wet plug problem though.

It sounds as if your float and float needle are working correctly. When the gas is opened, the float pin goes up, and no flooding, so that’s good. I’m not sure about the specifics of the fuel leaking around the venturi. When you prime the carb, fuel should come out of the open part but not from anywhere else.

There are two tiny packing washers around the low speed needle that sit on a concave seat. When the packing nut gets tightened, the washers get compressed around the needle and seals off air from getting in past the needle. They perform an important job. Do you have the packing nut tightened properly?

There is a procedure for removing the venturi. I have never had to do this, but I do recall reading that it is pressed in with lead shims. That would be the last thing that I would try, but who knows.

Bear in mind that the high and low speed systems take two different paths through the carburetor, and there could still be a blockage in the high speed system while the low speed and primer seem to work fine.

Improvise-Adapt-Overcome