Farmall Cub

What is the cause of the engine to pick up RPM"S on its own? I can pull the throttle back to an idle and then the engine gradually picks up RPM"S on its own! Can't tell if it is govenor spring not actually returning full back or what? Dusty B

Thinking on this one.

How far, rpm increase, does the engine speed up on it's own?

Edit. New or old issue?

Check for binding governor and throttle linkages, or just the opposite, extremely worn linkage clevises and pins.

Dusty, the spring does not return the carb. to idle, the spring increases the speed. Check the linkage, as mentioned above and also check the adjustment of the carb. linkage rod. If nothing is found there, you may have an internal issue with the governor.

Eugene wrote:Thinking on this one.

How far, rpm increase, does the engine speed up on it's own?

Edit. New or old issue?

Has gone up to approximately half throttle - never let it just go to see when it would quit. Started doing it this fall. It's on my snow blade tractor, may not get attention until warmer weather! Dusty B

Dusty:



I would apply your favourite brand of penetrating oil, liberally, to all of the linkages/connections in the governor circuit. It may be as simple as a little dirt/rust/crud binding up a tad. That would be the easiest route to go for now. If it doesn't solve the problem, in the spring you can delve deeper when it is warmer out.

Do this simple worn linkage troubleshooting step:

Engine off, speed control all the way to the rear, curb idle position. Grasp the lever on the carb side of the tractor that is connected to the governor rockshaft and linked to the carb throttle plate. You should realize no movement in either direction.

Advance the speed control all the way forward to high idle. Again, no movement in either the forward or backward direction should be realized.

Lastly, move the speed control lever to the center of its travel. Grasp the rockshaft lever and this time you should be able to move the lever forward closing the throttle plate.

When testing the lever for movement, don't do it with brute force, just attempt to move it lightly, you will overcome the governor spring if you twist on it too hard defeating the purpose of this test.

If in either speed control lever positions of fully forward or fully backward you are able to move the rockshaft, expect to find damaged or worn governor shaft linkage components.

I think you will find trouble in the governor itself
Boss

Boss Hog wrote:I think you will find trouble in the governor itself
Boss

In which case this would be of use : Lurker Carl's Cub Governor Rebuild

Most common reason for what you have described is Item #6.