3020 Zenith carb replacement..with Allis chalmers zenith

I have been asked about the Allis Chalmers carb that is on my 3020 that makes it run great. I didnt install it it came with it when I bought it and from what I learned they had problems with the original carbs on 3020s on adjusting and keeping adjusted. J.D. mechanic.(older guy) told me they used Allis carbs on them and they ran great. Mine was the first he had seen in all the years.. So for whoever is intersted here is the info.

The carb is a allis carb. #13327A (inner #) and oem#22025 (outer #) the tag is round size of dime which indicates original allis carb. This carb was originally installed on the allis chalmers 190 gass tractor. it is a Zenith carb and will bolt on to where the J.D. zenith bolts BUT is a tad smaller on the two flanges that bolt to intake BUT will work and has worked on my tractor for more than 15 years with little adjustments.

That is kind of interesting. I worked on a few carbs on 3010 & 3020 at deere dealership. Some of the guys liked the Zenith, some the Marvel Schebler and most didn't like either one much.

John Deere had a bad habit of oversizing the new generation gas engine carbs to get that last full throttle horsepower out of them to look good in the Nebraska tests and sales literature, but it made a gas engine that only ran decent at full load and full speed. Low and mid dirvability and mixture control was awfull.
I fixed my gas 4020 by substituting a little 283 CID moline (model U)carb for the original JD carb. It starts and runs so much better at idle to 80% load . If it lost any top end power, it would take a dyno to tell it, as I cant feel any less power by the seat of my pants . sure makes a much nicer working tractor out of it.

Two other problems those gas tractors had since new was the pathetically weak ignition system and starter.
I built a Delco MT25 starter to replace the wimpy stock 10MT starter and replaced the weak ignition resistor and point distributor with a powerfull solid state ignition system.

I now have a tractor with enough starter that it actually cranks so fast that it has to slow down to idle, it does not spit or smoke and it starts and runs in any sort of damp / wet weather.
Also due to the stronger ignition system, it has not fouled a plug or needed any plugs replaced in over 10 years.

Yep agree... I have battled the starter for years.. Replace plugs and points every couple years..