no fuel cold

[eriew]

I had old style carb. Threads corroded at adjustable jet. Was planning heil-coil solution to fix leak.

Instead, I came across a used new-style aluminum Zenith. Bought Moyer flame arrestor conversion kit and scavenger tube flange so no tap was required.

Worked well first time but now it is difficult to start. Heavy hand-choking and throttle open or putting gas in the spark plug holes before starting is necessary when cold.

Then it will start put for about 30 seconds it tries to stall and I give it more throttle and it runs. Then it runs fine when warm.

Seems like only the main jet is working. Is the scavenger tube needed for cold starts. Mine is too long so I bent it. I could cut it to so there is no loop. I noticed that the intake is very dry when cold and it doesn't get wet even after cranking. Normally, with the old iron carb it would get wet when cranked and heavily choked. The old style had the internal tube which was short and straight.

Any thoughts on why she won't prime?

[Don Moyer]

After 15 or 20 seconds of cranking with the choke completely closed (and the engine not starting), there should be raw fuel puddled in the bottom of the air intake of the carburetor in both early and late model engines. The fact that your engine runs normally after it warms up also confirms that the problem is limited to the choke. Unfortunately, I'm not able to determine from your report what may be preventing normal choking.

The additional length of your scavenge tube shouldn't have any bearing on your ability to choke the engine, unless it is somehow disconnected below the carburetor. In this case, air would be sucked in through the bottom opening and prevent normal choke function.

You might try removing the flame arrestor housing and holding your hand over the intake of the carburetor while someone cranks the engine over. If you don't immediately see large amounts of fuel collecting in the bottom of your intake throat, there is an air leak somewhere downstream of the choke valve.

Don

[eriew]

Don
I did try choking by hand and did not get the puddle of fuel that I would expect to see after 20 seconds. There is an air leak as you suggest. Now I have to locate this leak.

Can the leak be as a result of an open idle adjusting needle (way off from spec)?

Another possibility; the spacer flange for the scavenger kit lowers the carb enough that this flange barely clears the mechanical upper fuel filter housing. The rear threaded 1/8 inch plug has very little clearance. This may cause air leak at the pickup flange to manifold, but I think it is clear. May have to file down the flange or the plug to get clearance.

[Don Moyer]

Good for you, I think you're on the right track. Please let us know what you discover.

Don