Governor bumper spring

Sun Feb 09, 2014 2:07 pm

When I first got my cub I had issues with surging, and in my effort to solve it I screwed the bumper spring on the front of the governor waaaay in. as a result the engine was having trouble picking up under load. today i decided to see if i could fix the problem the right way, and i think i have. I cleaned all the linkage up with penetrating oil and made sure there was no rubbing. I also gave the carb linkage an extra turn or two to make up for the worn key in the rockshaft. I can now unscrew the bumper without the engine surging out of control. The only problem is i have no idea where it's supposed to be set! i've been unscrewing it by half turns and testing under load by lifting things with the touch control. so far i've gone about 5 full turns out (it was pretty close to all the way in before), and I've noticed a definite improvement in the response. I'm thinking if i replace the other spring (on the throttle rocker), i can improve even more, but how far is too far for the bumper? I guess if i have problems down the line with surging i can just screw it back in.. but what i was hoping to find is something like a procedure for setting it after a rebuild. anybody heard of such a thing?

Re: Governor bumper spring

Sun Feb 09, 2014 2:47 pm

Eoghan wrote: but how far is too far for the bumper?

When it starts to surge.

My approach when one was apart is to leave it WAY out then turn it in a bit at a time until the surging stop.

Re: Governor bumper spring

Sun Feb 09, 2014 3:44 pm

I pulled the screw out all the way until there was very little thread left, and could not replicate the surging that I used to get. the only thing i noticed is that if i jerk the throttle forward it revs up really quick, then settles at a normal rpm. is that normal? it seems like the governor is finally doing it's job though, because the rpm stays relatively low when the throttle adjuster is above 75%, and only seems to go way up when under load. it still drops a little at first, but it's much quicker than it used to be. I bet i'll have to push it back in some when i take it out and push some snow later.

Re: Governor bumper spring

Sun Feb 09, 2014 9:56 pm

You might want to be sure that the bumper spring hasn't broken, before you do any adjusting. There should be about 1/4" or so of the spring sticking out of its ferrule retainer. In my case, it turned out that the spring had broken off pretty much at the end of the retainer.

Re: Governor bumper spring

Sun Feb 09, 2014 11:16 pm

It sounds as if you have 2 problems. One is the cross shaft and/or key way is worn where it goes into the governor. Two is the bumper spring is too far out, It should not over rev then settle back, Three (so I lied about there being two), The spring mounted on the front of the governor is weak.
Four, the linkage may be out of adjustment between the cross arm and the carburetor, The procedure is in the owners manuals on either of the manual servers at the top of the page.

Re: Governor bumper spring

Mon Feb 10, 2014 12:18 am

Although I can't point you to a procedure in a book, this is what I do to set the bumper spring.

If you don't have a problem with surging and have good throttle response, and you've checked that the spring is intact....
1) back the bumper spring back out some
2) set the idle down to 500 RPM (may have to back the bumper out even more)
3) once the idle is set and the tractor is running smoothly at 500 RPM, slowly turn the bumper back in till it interferes with the previous idle setting.

Recheck your throttle response and for reoccurrence of surging.

Re: Governor bumper spring

Mon Feb 10, 2014 9:45 am

ok, so i checked and the bumper spring IS intact. I also know the throttle spring is probably weak, so im ordering a new one today.

raymond: Regarding your procedure, where should the control lever be? to set idle i assume all the way down at zero? or 25%? I like the sound of that method, but I didn't realize the bumper would affect the idle.. when turning the screw in, the idle should go up at some point?

John: you're right about at least one thing, the keyway on the carb linkage is definitely worn. it wiggles about 1/8 inch. i had read somewhere about taking up the slop with a turn or two of the arm at the carb, so i did that, and it certainly makes it tight when the control lever is all the way forward (engine off). instead i'll just throw some jb weld in there and take that out of the equation. I'm thinking that's probably the cause of my little surge and return. if it's still there after that i'll push in the bumper until it stops.

Thanks guys!

Re: Governor bumper spring

Mon Feb 10, 2014 6:14 pm

Eoghan wrote:....
raymond: Regarding your procedure, where should the control lever be? to set idle i assume all the way down at zero? or 25%? I like the sound of that method, but I didn't realize the bumper would affect the idle.. when turning the screw in, the idle should go up at some point?

...

Yes, to set the idle, you'll need the throttle lever pulled all the way back.
When the idle is set and the tractor is running at 500RPMs, if you turn the bumper spring in till it hits the finger inside of the governor, it will start increasing the RPMs. You want to turn the bumper in till the RPMs increase a bit and then turn it back out till you get back down to your original low idle setting.
If you have slop in the linkages, fix that and replace the governor spring before you set the bumper spring.

Re: Governor bumper spring

Mon Feb 10, 2014 6:50 pm

thanks raymond, I spent some time on it today, and got it settled in a spot where the revs are fairly smooth. I think It's farther in than it ought to be because it's making up for the slop caused by the old governor spring. I managed to squeeze a piece of aluminum in the key slot and stabilize that piece, but i think the spring holes there are wallowed out a bit, so i'll have to fix that somehow..

Re: Governor bumper spring

Mon Feb 10, 2014 7:47 pm

There are several ways to fix the wallered holes, but they require removal for access. One is to fill the holes with weld and then redrill a smaller hole. The other is to find an appropriately sized roll pin and use it to reduce the hole size. There may be a "how to", but I didn't look for one as I think both fixes are fairly self explanatory.

Bob

Re: Governor bumper spring

Mon Feb 10, 2014 8:33 pm

I think i'll probably remove the governor when it's not so cold in the shop and give the whole thing a good once over (bearings, seals, springs, etc). I might try to weld and re-drill that hole, but to be honest i'm not that confident with the welder yet.. would it work if i just fill the hole in with jb weld and drill that out?

Re: Governor bumper spring

Mon Feb 10, 2014 8:37 pm

It would probably work short term, but I think the JB would wear a lot quicker than cast would. Depends on how much the tractor will be used too.

Bob

Re: Governor bumper spring

Mon Feb 10, 2014 9:13 pm

I have used the roll pin technique to solve the sloppy hole problem on several Cubs it works very well.

Bill

Re: Governor bumper spring

Tue Apr 15, 2014 9:45 am

Bill Hudson wrote:I have used the roll pin technique to solve the sloppy hole problem on several Cubs it works very well.

Bill


Do you peen the end of the roll pin to keep it in place and can you point me to where I can find a bumper spring? I haven't come across one of those with any of the parts dealers.

Re: Governor bumper spring

Tue Apr 15, 2014 10:11 am

The cast lever is a little fragile, so I'd be careful about peening it. You can probably end up with a tight enough press fit, or use some JB to hold the roll pin in place. TM Tractor (sponsor at the bottom of the page) has the springs.

Bob