Curse this Surging Throttle!!!

[ElementGardens]

My Super A is throwing a fit. Help me diagnose it? See the video link below for an in depth breakdown.

https://www.youtube.com/watch?v=31lbyaMsB7U

I dont know the year as the serial number plate is missing, but I suspect a 50 or 51 maybe. The Zenith carburetor that was on it when I got it started acting up and skipping and shutting off, so I pulled it and cleaned it thoroughly. New gaskets and everything, but when I put it back on, it refused to start. The bowl fills up with gas, but its not getting into engine for some reason. New carburetor fires right up and runs great, except that it surges really bad. It makes it undriveable except at just above idle. If you give it anymore gas then that it revs up and down uncontrollably. Spring and bearing inside governor appear fine, although there is a little bit of play before spring engages and a little slop side to side on rod inside governor. It does not surge at all if you unhook carb from governor, though, which makes me suspect its a gov issue, not carb, and I drained all old gas and cleaned tank and put on inline filter, so fuel should not be and issue.

https://www.youtube.com/watch?v=31lbyaMsB7U

[Jim Becker]

The governor speed regulation works by a pretty simple concept. However, there are quite a few individual pieces that have some effect on the behavior and can contribute to surging. Even something as small as carburetor jet size can make a difference. So yes, changing to a different carburetor can cause it. I also wonder about the patched lever on the governor. Is it the same length as the original? Hard to tell from the video, but it looks longer to me. Replacing it with a good original may fix your problem.

In your situation, I suggest these steps in this order:
1) Since you have the governor off: Look on the bottom for an acorn nut. Remove it, exposing a stud with a locknut. Remove the stud, keeping the locknut position to maintain the adjustment (how far the stud is screwed into the governor housing). There will be a bumper spring in the inside end of the stud. You may find the spring rusty/broken. Clean and oil the spring or replace it if needed. Reinstall the stud, maintaining the original adjustment. Reinstall the governor.
2) Double check your carburetor adjustment. Make sure the idle mixture gives a decent idle and also avoids any stumble when the throttle is opened.
3) Make sure the linkage from the governor to the carburetor is adjusted (engine off, control lever forward, throttle open, pin should just slide in where the rod and lever connect). Verify no binding.
4) Test for surging. Steps 1 through 3 may cure it. If not, do step 5 until it quits surging.
5) Adjust the stud in a little at a time until the surging stops.

[ElementGardens]

Thanks Jim, I think you solved my problem. I pulled off the adjustment screw underneath the gov and low and behold there is no spring at all. That probably explains a lot doesn't it? I've ordered a new one, so we'll see how it goes.