The Stovebolt Site Forums The Parking Lot Big Bolts Carb rebuild kit for Zenith one barrell

Zeiniths are not hard to overhaul but you do need to take your time and make sure everything is squeeeky clean. Also accuracy in measurement counts. Fuel pressure is also important. Also bear in mind that alcohol in the gas will make things run leaner and if you're working the truck hard can have bad results. I have had valve stems stick and temporarily stuck a piston when I picked up a tank of gas with too much alcohol. One eights turn on the main jet fixed that. These zenith carbs were available with adjustable main jets. I have two. I don't know if they are available now but it's worth asking.

One thing often overlooked is throttle shafts. When these wear they leak air and the idle speed won't be consistent -- sometimes high, sometimes low sometimes rough sometimes smooth. You need a drill press and a reamer to do this properly as you need to get the bushings on both sides square and concentric. This is a job I used to do frequently on SU carbs and now need to do on both Zenith carbs on my 235 so I'll have to come up with bushings and a new reamer. I don't know if new throttle shafts are available and it's not something one can fabricate easily. Bushings should not be a problem. It's a ream to fit proposition. If someone knows where to get throttle shafts, I like to know.