630 Surging Issue

I recently rebuilt the carb and relined the gas tank on a 630. After a couple shop towels that got stuck up inside the air cleaner, the tractor is running pretty good after sitting for three or four years.

I have noticed though that after driving it down the road at full throttle and then stopping and idling down, it surges up and down several times before it levels off. The tractor starts and idles fine, it just seems that after I give it a good running and then throttle down and park it does it want to do this surging.

I have read a few of the previous posts on governor and/or carb issues. But does this sound like a carb issue or a governor issue? I havent done any tinkering with the governor and am afraid to open it up and start messing with parts until I check here first.

On another note, thank you so much for everyone else over the last couple months that have posted responses to my posts on this tractor. I am not the most mechanically inclined person, but it was extremely rewarding to hear this tractor run and stay running after all I did to make it work. There were lots of proud people in my family that finally got grandpa's "put-put" running and going down the road!

It sounds more to me like either binding throttle or a governor link adjustment. Throttle shaft can wear causing the butterfly to drop down and drag in the bore of the carb, shims under the throttle actuator on top of the carb might help that or new bushings/throttle shaft if really bad.

Work the throttle open and closed by hand with the engine off, it should not hang at any point. Then push the hand throttle full on and disconnect the governor rod at the carb, the throttle is supposed to be able to move 1/2 hole further open than the governor rod can push it. Some tweaking is allowed here for example a straight drop in at wide open throttle, or in the other direction a whole hole short, but it's really sensitive so one turn of rod adjustment at a time and take it for a test spin.

Not much to do inside the governor in this regard except to overhaul it, replacing obviously worn out parts, pretty rare to find any so bad that they won't work right in the first place. I'd stay out of there unless no joy can be had any other way. Very involved to get the governor off so a good job can be done on it. So I would adjust the load and/or idle screws 1/4 turn at a time on the carb hoping that this would help before pulling the governor as well.