Model C with rpm problem

When I set the throttle position for a higher RPM on my 1948 model C, it almost immediately jumps back to the lower RPM position. I can hold it there or put a clamp on it to keep it so I can use the tractor, but I am thinking something is out of adjustment. Is it the governor or something else?

Thanks for any advice and I hope everyone has a Merry Christmas!!

Is the lever popping back, too, or does engine speed drop while the lever stays forward?

Is the lever popping back, too, or does engine speed drop while the lever stays forward?

The engine speed stays high only when it is forward. When the lever pops backward, the engine rpm returns to idle.

Get a new throttle quadrant and lever or maybe you can file a deeper notch at top rpm.

The engine rpm should drop when the lever is pulled back. The throttle plate has notches to hold the throttle in a given position. Several things could have happened. On one of mine the tooth on the throttle handle was worn down. We welded a small bead on the tooth and then I filed it down to a sharp point. Another thing could be that the grooves in the stationary part of the throttle plate have been round over through years of wear. It is also possible that the bolt holding the throttle lever is not tight enough. There is a spring in there and this may be allowing the throttle to drop back to the idle postion. O.E.M. Tractor parts has the entire throttle assembly for $68.00 or the throttle handle for $32.00. You could probably also get through your CASE/IH dealer.

Thanks everyone. I appreciate the help. And once again, Merry Christmas and Happy 2009!!

IF I'm reading it right, the lever pops back to the low idle (or at least a lower speed) position on it's own.

That suggests that your governor is working fine, but that either the teeth on the throttle quadrant or the tooth on the lever are worn to a point that they won't hold against the tension of the governor. NOT at all unusual. It comes from years of somebody just slapping the lever forward, letting the teeth ride over each other.

It may also be as simple as the spring on the hinge pin of the lever is weak, missing or part of it broken off. Look first for the spring. There should be a cotter pin holding a washer that keeps the spring compressed over the pin and against the lever.

It's actually a pretty strong spring for no bigger than it is. When you pull the lever away from the quadrant, you should feel a good bit of tension, that is used to hold the lever in the notches. Not sure whether CaseIH still carries it or not. If that's a problem, you might also be able to find one that will do the job at a hardware that has a good assortment of springs.

The other issue is wear. If the teeth/notches on the quadrant are rounded over, they may not be holding like they should. New, the serrations were flat/perpendicular at the rear edge and angled forward to the next. The tooth on the lever will often have a deep notch in it where it rides on the quadrant. Wear on either side (lever or quadrant) will cause the problem, and is often a combination of the two.

There's always the replacement option. OEM has them, I believe.

For repair, the notch worn on the lever needs to be welded in and ground back down to match the unworn area. The quadrant is a little trickier, as you don't have much depth to work with there, but a triangular file or grindstone can be used to dress them up some. Just keep the back edge of each notch perpendicular to the plane of the quadrant.

HTH

I found the problem thanks to all you folks. The tooth on the throttle handle is no longer there. I will replace it. The spring and notches on the plate are fine.

Good job!

Had the ssme problem with my Cub. Built it up with a spot of weld and dressed it down with a file. Works fine. Another little fix I did. Installed a turnbuckle in the throttle shaft to take up the wear in the spring and lever where it hooks on to the governor. That helped a lot. Before I did that there was no response from the throttle lever until it was half was open. rw