72 Ford 2000 Zenith carb question

[TomGator]

I have this 2000 that starts and runs ok, but pops and misses on any speed increase. I replaced the points, sap, rotor, plugs, condenser, timing set at about 3 degrees btc. I also cleaned the carb, but did not have a kit to do it properly. The carb is a zenith, with no numbers on it that i can find. Just Zenith stamped in. 3 cyl engine. I ordered a carb kit and removed the carb again while waiting on the kit. I do not understand how the carb works. i understand basic carburetion and have been an outboard engine tech for 50 years. I'd like to know the function of the diaphragm assembly on the bottom of the carb and how it works as well as the proper assembly of it as well as the rest of the carb if possible. i have searched google and you tube but cant seem to find anything showing that bottom part of the carb bowl. Any suggestions? Thanks

 

[ROBERTJONES]

Hi TOM, I had seen your post a while back and I couldn't find it
again. I just ran across it again and what caught my eye was the
pop and spit as you increased your throttle. If I'm reading that
right, yes.. Ok. Yes. I had the same issue with my 73 2000. I
started with the carburetor, spent a lot of time and money.. could'nt
fix it. bought a new Zenyth carb, it ran better but still had the same
issue. On your distributor. Do you have a vacuum diaphragm? If
so, check if it's holding vacuum. If it's not, there's your issue. As
you increase the speed the vacuum advances the timing. If it
doesn't advance the timing, the tractor will snort, pop, backfire
something fierce! I replaced the distributor with a mechanical
advance model, and Whammo! it took care of the issue. I tried to
replace the vacuum diaphragm. No luck. They say it is no longer
in production. There is a guy that rebuilds them but it was $175.00.
The new distributor was $150.00+-. I'm happy I found your
question... Changing out the distributor to a mechanical advanced
model solved the same problem you have. Ask around for a
second opinion if you think it may be something else... I just
remembered your post while I was fighting my tractor setting
timing... float levels.. on and on. Let me know what you think and if
you want to spend the money I will send you the part numbers. I
bought the distributor from here Yesterday's Tractors. Good luck,
and if I can help just Email me, or post to me however that works.
Be well. If you get the new distributor, remember to block off the
vacuum line that went to the diaphragm...

 

[ZehnX]

The best explanation of a carburetor I've ever seen is a YouTube video from Smarter Every Day. Search for "smarter carburetor" and you'll find it.

There are also good diagrams in (my) tractor service manual. If you don't have one, I could send images.