OK, my 1949 AC B with a Zenith carb hasn't run right since I bought it. It runs fine from 1/2 throttle up (notch 6 and above) but under that I had to keep the choke out to keep it running - and the air screw was all the way in, too. Backing it out resulted in loading up with fuel.So I pulled the carb apart, cleaned it, adjusted the float setting (it was too high), and added an inline filter. Put it back together and the same problem, but now I could back the air screw out almost 1/2 turn .... argh! Aggravating since I have a 1950 B with an MS carb that runs like a sewing machine. Last week I was talking with the guy I bought the 1950 B from (he's *big* into John Deere L and LA tractors). He asked if the venturi was loose - why yes, it is. He then told me that if it's loose it will actuall rotate around in the carb while the engine's running and do all sorts of weird things. The fix - take the carb apart, remove the gasket and set the two halves of the carb back together. If the body and top fit flush then the venturi's too loose. Make a *thin* washer and fit it around the venturi so there's a small crack between the body and top of the carb when it's put together without the gasket. When I got home I checked and sure 'nuff, the carb body and top fit together flush without the gasket in place. So, I got a piece of 18 gauge aluminum electric fence wire, made a cirle, and beat it flat with a hammer - probably 0.010 or maybe 0.015 inches thick (a guess on my part). I fit this washer around the venturi just above the 4 flanges on the bottom so the washer would be between the venturi flanges and the top part of the carb when the venturi was installed. I put it back together and the difference was astonishing. Now it idles down to 1050 rpm with an occaisional miss and I'm sure I can get it down further with a little adjustment (my 1950 will idle smoothly down to 750 rpm without a miss - it's sweet!). The tractor even runs better at load, and the governor works like it's supposed to (before when the governor cracked open it was liable to "flood out" immediately if I wasn't careful). Man, that tractor runs good. Not as good as my 1950 B yet but I'm on the way. Some of you may know about this fix but it was news to me - and it saved me a bunch of heartache. Older mechanics sure are a pleasure to be around!
| 
