Governor Spring/High Idle RPM Question

[TallCoolOne58]

For what it's worth: 1957 Farmall Cub, 6V, battery ignition.

Last summer, I performed an ignition tune-up. As part of that, I set the ignition timing to 16 degrees BTDC @ 1600 rpm, per the manual. At the time, I noticed my no load (trans in Neutral, brakes locked, PTO off, clutch engaged) high idle rpm was 1643. I had always thought that by ear it wasn't achieving 2000 rpm's.

I made a mental note to purchase a new governor spring, along with other items, for my baker's dozen to-do list when I pulled the hood last fall. I did pull the hood, but since I did not write my to do list down, naturally the one thing I forgot to do was replace the governor spring. (I can't beat myself up too bad, I did a lot).

My Cub still has the wire and lead seal "tattletale" on the governor high idle rpm limit screw. I am hesitant to adjust it, at least until I have had a chance to replace the spring, as it was 'right' when it left the factory, and I would like to exhaust other possibilities before I perform that adjustment. ( I have lubricated the linkages and shafts, and also replaced the rocker shaft woodruff key).

After all that, my question is this- how much would a worn/stretched/tired governor spring affect high idle rpm?

Edit: I have no evidence of a 'stretched' governor spring, so I guess my question would be how much would or could a 'potentially weak' spring affect high idle rpm's?

[Gary Dotson]

It depends how worn, stretched and tired it is. There is no definitive answer to your question. Make sure you're getting full travel on your throttle and that the governor lever is making contact with the adjustment bolt tip. I would, then, unceremoniously snip the wire and adjust it.

[TallCoolOne58]

It depends how worn, stretched and tired it is. There is no definitive answer to your question. Make sure you're getting full travel on your throttle and that the governor lever is making contact with the adjustment bolt tip. I would, then, unceremoniously snip the wire and adjust it.

Yeh, that and replacing the governor spring, and checking results with tach, seems to be the only logical answer.

[TallCoolOne58]

I guess the bottom line is, I was curious to know if someone had been in a similar situation, and had noticed more rpms @ high idle after replacing the governor spring.

[inairam]

I guess the bottom line is, I was curious to know if someone had been in a similar situation, and had noticed more rpms @ high idle after replacing the governor spring.

You would expect more rpm from the tighter spring.

What you did with the new and tighter spring is change the operation of the carb to / gov linkage. You should be able to adjust it out with the carb/ gov linkage and not have to touch the wired bolt on the governor.

[TallCoolOne58]

I guess the bottom line is, I was curious to know if someone had been in a similar situation, and had noticed more rpms @ high idle after replacing the governor spring.

You would expect more rpm from the tighter spring.

What you did with the new and tighter spring is change the operation of the carb to / gov linkage. You should be able to adjust it out with the carb/ gov linkage and not have to touch the wired bolt on the governor.

I gotcha. After replacing governor spring, check carb to governor linkage, adjust as necessary. Check high idle rpm with tach. Then, if needed, adjust the governor high idle rpm limit screw to achieve the 2000 rpm.

[inairam]

I personally am not too worried about the top RPM. The same engine C60 in a bailer or other " stationary" applications was set to run at 2500 RPM. The later cubs the numbered cubs had higher than 2000 RPM limits.

Your max torque is at 1600 so that is where you want to be to pull stuff. A faster engine means a faster PTO which is what you want to cut grass.

I would not cut the wire to adjust the nut to bring the RPM down. I have a 49 that still had the wire in the nut for the governor and I cut it off. I still regret doing it. I think the engine is fine if are at 2100 or 2200 with the throttle at max. Just do not run it max.

Save the last two or three notches on the throttle when you have to run from the law!

[ntrenn]

Normal governor droop is 150 rpm. Set your no load 150 rpm above the governed speed you want...1950 for an 1800 rpm engine.

That will assure you have full fuel at the desired loaded speed.

[TallCoolOne58]

I personally am not too worried about the top RPM. The same engine C60 in a bailer or other " stationary" applications was set to run at 2500 RPM. The later cubs the numbered cubs had higher than 2000 RPM limits.

Your max torque is at 1600 so that is where you want to be to pull stuff. A faster engine means a faster PTO which is what you want to cut grass.

I would not cut the wire to adjust the nut to bring the RPM down. I have a 49 that still had the wire in the nut for the governor and I cut it off. I still regret doing it. I think the engine is fine if are at 2100 or 2200 with the throttle at max. Just do not run it max.

Save the last two or three notches on the throttle when you have to run from the law!

Right now my max is 1643. I want to adjust it up to the specified 2000.

Edit: outrun the law...on a Cub. Now that's funny. I do live in the country, but unfortunately on a busy road. Getting from the house to the other acreage 300 yards down the road, as quickly as possible, usually hauling a trailer, is advantageous.

[TallCoolOne58]

While we're on the subject. Torque-a body at rest tends to stay at rest. Torque gets a load moving. Horsepower- a body in motion tends to stay in motion. Horsepower keeps a load moving, and allows you to overcome obstacles, like hills.

Here's the smart play. Hook up a tach to your tractor. Find the throttle lever notch that gives you 1500-1600 rpm, for max torque. Set the throttle lever to that notch when starting to pull a load, like a trailer. Once moving and stable, adjust throttle up from there.

[Gary Dotson]

The governor to carb linkage should be adjusted using the procedure in the service manual, that syncs. the governor to the throttle plate. It should NOT be used to adjust RPM! While it will change the RPM, it will also effect the sensitivity of the governor.

[inairam]

I agree with Gary. You should be able to get to 2000 rpm without cutting the safety wire. Something else is not right.

When you had the hood off did you remove the rod between the throttle and the governor? if so are you sure it reinstalled properly? The rod will go in both ways but it will bind if backward. There is a governor end and throttle end to that rod. There also could be some cotter pins on the links at the carb that is restricting it.

Check everything else before you consider cutting the wire and adjusting the governor

[TallCoolOne58]

Everything is/was installed, adjusted and working properly. I can see the lever move freely and stop against the governor rpm limiter bolt at full throttle. When engine is running and I adjust throttle lever, I can see governor to carb throttle linkage moving freely.

It's not something that I did. The high idle rpms are the same as when I bought the tractor, even after removing the carb for a thorough cleaning, setting float level and float drop, adjusting linkage etc.

One clue that I have about governor spring strength/ weakness tho, (or, perhaps hole enlargement due to wear). When I move the throttle lever to parallel with steering shaft support (12:00 position), the point where tension on the spring should be just starting, rpms only go up about 100-150 from low idle. Spring appears to have minimal tension, if at all, so little it's difficult to tell by eye. I use that as my 'cold start' position. If I adjust carb to governor linkage in this position, rpms are notably higher, but moving the throttle lever either way does not change the rpms, it stays on 'high idle'. If I move throttle lever to high idle position to make this adjustment, full tension on the spring, then all works as it should, but high idle rpm is lower than it should be. Thus the new governor spring.

I'll replace the governor spring, and, with the help of my lovely assistant, visually check spring tension as the throttle is moved forward a notch at a time. I will check governor to carb linkage, and adjust as necessary.

I'll figure it out. It's bugging me, and I like things to work properly. I really don't want to cut the wire, and I will exhaust all other possibilities.

Edit: Edited for clarity

[TallCoolOne58]

The governor to carb linkage should be adjusted using the procedure in the service manual, that syncs. the governor to the throttle plate. It should NOT be used to adjust RPM! While it will change the RPM, it will also effect the sensitivity of the governor.

That is my intention Gary, to adjust per the service manual, after replacing the governor spring.

[Glen]

Hi,
The low idle speed should be set at the adjustment screw near the top of the carburetor, on the engine side of the carb. It is the screw with the spring on it.
Below is a pic from TM Tractor of the IH carb.