Overrunning After Carb Cleaning

[ctltmp]

Well whoever said will it ever run as good after cleaning it was right.

Fired right up but I have no low end throttle control. It idles about 800 I estimate. I'm able to push the governor and get more but it won't come down.

I only cleaned the carb and replaced gaskets. Same needle and seat and made no float adjustment.

I'm puzzled. Any wisdom is appreciated.

[Don McCombs]

Did you re-adjust the carb-governor linkage per the service manual? If not, I would suggest that you try that first. It also can't hurt to check the float adjustment.

[ctltmp]

Don I did readjust the linkage. I figure since I didn't change the needle and seat or mess with the float it wouldn't matter.

Thanks

[tst]

by any chance did you reverse the choke/throttle linkage

[ctltmp]

Nope. Choke and throttle hook up is correct. Glad you asked though, could happen.

[Lt.Mike]

Check for a vacuum leak. Spray carb cleaner or starting fluid around gaskets to see if you get an rpm jump or drop.

[inairam]

Don I did readjust the linkage. I figure since I didn't change the needle and seat or mess with the float it wouldn't matter.

Thanks

You did or did not readjust the linkage? The way this reads it sounds as if you did not.

No matter what you should readjust the linkage. I do not know the physics of it but just taking it off and putting it on charges something. Always re adjust the linkage.

Also, check for a vacuum leak.

Also lube the linkage connections, check cotter pins on the choke and governor linkage and trim if too long ( had a problem) and you may also have to adjust the idle screw and the fuel-air mixture screw.

[Rick Spivey]

Have you tried back g out the idle speed adjustment screw? I can only assume your idle circuit was partly or fully clogged before, and someone had run it up to compensate.

[ctltmp]

Guys,

Initially I did not readjust, then I did readjust the linkage after the speed was overrunning. When I first brought it home it was idling high. I was able to adjust the idle screw to get it to idle correctly. Since it's "cleaning", I also did try to adjust the idle screw to compensate until I ran out of adjustment. There's no throttle control at all. Move it forward or backward it stays the same speed and the governor linkage isn't moving at all with the throttle.

I'm leaning toward agreeing with Rick that something was clogged and it was adjusted to compensate. If you look at an earlier post where I have a picture of the gasket you can see probably why it would be. My belief is that everything is original on this cub, including believe it or not the plugs (or they have been in it forever. Never seen anything like it. I hesitate to even try to get them out, but I know they have to be replaced. Looks like maybe rust welded to the head.

Also noticed that at first look maybe the thread length of the control rod is short. Doesn't seem to be as much thread as there is on the 49. Someone may have cut the rod off some at some point. I'll take a measurement after work if I get a chance to work on it.

[Gary Dotson]

During the carb. work, did you remove the throttle plate? There is a procedure for centering the plate when it is reinstalled. Basically, back the idle speed adjust screw out until it no longer contacts it' stop, hold the throttle plate fully closed and tighten the screws. I've run into several Cubs that would not idle down and that is usually the problem, assuming everything else is as it should be. That can also cause the throttle plate to hang up in it's bore, causing erratic throttle response.

[ctltmp]

Gary, no, didn't remove the throttle plate.

[Urbish]

An easy test would be to remove the linkage between the governor and the throttle and manually move the throttle while being careful not to over-rev the engine. If the throttle butterfly is moving as it should and can achieve all desired ranges of RPM, then that would point to something funny going on with your governor or with how the linkage is attached.

[Jim Becker]

An easy test would be to remove the linkage between the governor and the throttle and manually move the throttle while being careful not to over-rev the engine. If the throttle butterfly is moving as it should and can achieve all desired ranges of RPM, then that would point to something funny going on with your governor or with how the linkage is attached.

This is a good next step. If the results point to a problem in the carburetor, check the centering of the throttle plate as Gary described. The plate may have already been misaligned when you got the tractor.

[ctltmp]

Thanks guys. I had actually thought about removing the linkage and moving the throttle by hand, but wasn't sure if that was a wise move or not.

I have my work cut out.

[Waif]

Was the new gasket too wide and now causing an obstruction?
Depending on carb. style , was the top checked for warp?

What condition is the idle tube in?
Back feeding it air through the air adjustment screw hole might disclose a clog. It's a pretty small hole. I'm not saying you did not clean it, or that you plugged it.

Did the throttle stop screw get turned while cleaning the carb?

Instructions for adjusting the idle has the quadrant at operator station putting tension on the throttle. That can be halfway through the range of teeth on some tractors ,elsewhere on others.
More important might be running the control up and down it's range in between adjustments of the air screw to find the compromise between high and low range.
The governor is not as actively involved at lowest speed ,so running the throttle up and down between adjustments gets it's involvement noted.