Farmall Cub Surging- Solved!

R

RunningRed

Well-known member
Hey fellas I got everything back together today and good news, I don't have any leaks as of yet. Just have to figure out something with the overflow tube. Anyway back onto the question at hand. As you guys know or may not know, I went through and rebuilt all of the ignition system so everything is new and also copper core for plugs and wires. I also went and timed the cub to 16 degrees and set the low RPM and the high idle was right on at 1850RPM as stated in the manual. However, I always could never get the cub to run right if I adjusted the governor linkage as per the manual. Well it's something I want to finally figure out. When adjusted as the manual states it is hard to start and it kind of a pain to get to idle but when I do get it to idle it sounds good. When I give it a higher throttle it starts to hunt and surge. Now if I grab the governor linkage and hold it and then let go real easy the surging will stop. I checked the governor spring for stretch but it looks good, the hole the spring goes through is worn some but not a lot. Last year I also took all of the slop out of the shaft keyway and machined a new support bushing for the piece that connect to the throttle linkage. I only ran the cub for 15-20 minutes leaving it warm up but when I pulled the plugs they were fouled up with dry black carbon. I cleaned them before I ever ran it today also. Last year when I checked them they were black then also. I tried turning the screw on top of the carb but a half turn either way shuts the tractor off Hopefully I have enough information to maybe get one of you guys pointing me in the right direction.
 
Also I checked for air leaks and didn't find anything. I did a compression test before and all cylinders were right at 98psi. The factory specs for my year 1953 is 107psi.
 
You might read up on the Governor Bumper Spring...here is just one I came across, but there are probably others...maybe a HOW TO...
E

Thread 'Governor bumper spring'

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...

I tried Googling "function of Farmall cub governor bumper spring", and it gives a fairly good explaination.
 
Dale Finch said:
Here's another post I found regarding surging, etc.

Farmall cub Governors - Yesterday's Tractors

I have a 48 cub and the keyway on the gov. rod had slop but i have fixed that. Can any one tell me how to adjust the gov. to make sure its right. Also
www.yesterdaystractors.com
Click to expand...
Thanks Dale, I'll be sure to read those. I read about a bumper spring before but was trying to avoid that until I ruled everything else out but I guess I could mark it somehow so I can turn it back. I could really find much in the manuals about it unless it missed it.
 
Don't know if this will help, but I here is a composite I just made of what my I&T Manual says regarding the governor adjustments.
CubGovernorITsm.jpg
 
Warning! Do not try to adjust that bumper spring while it is running...the clearance (or lack thereof) can really bite you!!!

I'm sure I read a really good write up about adjusting the bumper spring somewhere in the manual...probably somewhere here...I'll let YOU try to find it!
Suggest you start on 2-12:
file:///C:/Users/Dale/Documents/TRACTORS/Manuals/SERVICE%20MANUAL%20GSS-1411%20W-Rev%201%20Cub%20and%20Lo-Boy%202-76%20OCR%20(1).pdf

As for me, I am late for my wine!!!
 
1000002334.jpgThis was going to be my next question, when I check the RPM I used a photo sensor that used reflective tape. I put the tape on the backside of the pulley on the part that slides over the crankshaft. I see in this image posted by havoc it says Belt Pulley - 1487rpm? Where is the best place to put reflective tape to get a true reading of RPM?
 
RunningRed said:
Where is the best place to put reflective tape to get a true reading of RPM?
Click to expand...
They are talking about a different Belt Pulley in that manual than the pulley on the front of the engine.
The Belt Pulley Attachment is an option, and goes on over the PTO shaft. It has gears in it, and is used to run a long belt, to power farm machinery, used when the Cub was new.
The pulley on the front of the engine, with the timing marks on it, runs at engine speed.
Below is a page from the 1950 Cub owner's manual telling about the Belt Pulley.
https://farmallcub.club/rudi/farmal...k Farmall Cub Owner's Manual 1950/Page 55.jpg

Below is a picture of it from TM Tractor Parts, without the wide, flat pulley on it.
 

Attachments

  • Cub Belt Pulley.jpg
    Cub Belt Pulley.jpg
    43.9 KB · Views: 1
Last edited:
I would think you'd be just fine putting the reflective tape on the engine crankshaft pulley. I think the Belt Pulley RPM number is what the belt pulley should be at when the engine is at high idle.

EDIT: I see Glen beat me to the punch, good thing, because for some reason I didn't even make the connection that one might think "Belt pulley" would mean the belts and pulleys on the front of the engine lol. Yes Its talking about the belt pulley on the rear that would be use to drive stationary equipment like saws or corn grinders or whatever. Here is a old photo of the belt pulley on my Super A, the Cub is similar albeit scaled down:


SuperAbelt.jpg
 
Last edited:
Another quick question that relates to this, well kinda. When you are timing the ignition on Cub which side of the pointer would be labeled as BTDC? Above the pointer towards to head of the engine or down towards the floor? I am asking this because the manual states to NEVER time it before BTDC. Now Its my thinking that anything above the pointer would be considered BTDC correct? I have a timing light that I can turn a dial to 16 degrees but when I do and use it I should see the timing notch right on the pointer or a little past towards the floor correct? I've been doing a lot of reading on this sleepless night now I confused myself. 1000002335.png
 
It's easy to time the engine.
Use the words below the picture to identify the marks.
Use only the words there, they are talking about other things on the page.
Set the timing at mark number 1 in the picture in the service manual, when the engine is running at slow idle speed, about 500 RPM.
Then as you slowly speed up the engine, the timing should advance to mark number 2 at full speed, 1800 RPM for a 1953 Cub, I think your Cub is a 1953. Mark number 2 is BTDC, like it says below the picture.
A 1953 Cub may not have mark number 2, it may only have the TDC mark.
If it only has 1 mark, watch as you speed it up, the timing should change to be about 1/2" advanced on the pulley from the TDC mark.
IH started using the 2 marks in about the mid 1950's.
 
Last edited:
RunningRed said:
Hey fellas I got everything back together today and good news, I don't have any leaks as of yet. Just have to figure out something with the overflow tube. Anyway back onto the question at hand. As you guys know or may not know, I went through and rebuilt all of the ignition system so everything is new and also copper core for plugs and wires. I also went and timed the cub to 16 degrees and set the low RPM and the high idle was right on at 1850RPM as stated in the manual. However, I always could never get the cub to run right if I adjusted the governor linkage as per the manual. Well it's something I want to finally figure out. When adjusted as the manual states it is hard to start and it kind of a pain to get to idle but when I do get it to idle it sounds good. When I give it a higher throttle it starts to hunt and surge. Now if I grab the governor linkage and hold it and then let go real easy the surging will stop. I checked the governor spring for stretch but it looks good, the hole the spring goes through is worn some but not a lot. Last year I also took all of the slop out of the shaft keyway and machined a new support bushing for the piece that connect to the throttle linkage. I only ran the cub for 15-20 minutes leaving it warm up but when I pulled the plugs they were fouled up with dry black carbon. I cleaned them before I ever ran it today also. Last year when I checked them they were black then also. I tried turning the screw on top of the carb but a half turn either way shuts the tractor off Hopefully I have enough information to maybe get one of you guys pointing me in the right direction.
Click to expand...
Sounds like you’ve had everything apart but you may want to double check to make sure that a piece of the linkage to the carburetor is not rubbing against the engine block. I’ve seen this problem on several cubs and every time I’ve found that the linkage from the governor to the carburetor is dragging against the engine block, or grease/dirt had built up in that area and was allowing it to touch. Even if it’s touching just a little, it causes the delay in response from the governor and makes it hunt and surge.
 
gitractorman said:
Sounds like you’ve had everything apart but you may want to double check to make sure that a piece of the linkage to the carburetor is not rubbing against the engine block. I’ve seen this problem on several cubs and every time I’ve found that the linkage from the governor to the carburetor is dragging against the engine block, or grease/dirt had built up in that area and was allowing it to touch. Even if it’s touching just a little, it causes the delay in response from the governor and makes it hunt and surge.
Click to expand...
Thanks I'll check it again
 
Glen said:
It's easy to time the engine.
Use the words below the picture to identify the marks.
Use only the words there, they are talking about other things on the page.
Set the timing at mark number 1 in the picture in the service manual, when the engine is running at slow idle speed, about 500 RPM.
Then as you slowly speed up the engine, the timing should advance to mark number 2 at full speed, 1800 RPM for a 1953 Cub, I think your Cub is a 1953. Mark number 2 is BTDC, like it says below the picture.
A 1953 Cub may not have mark number 2, it may only have the TDC mark.
If it only has 1 mark, watch as you speed it up, the timing should change to be about 1/2" advanced on the pulley from the TDC mark.
IH started using the 2 marks in about the mid 1950's.
Click to expand...
Thanks Glen, I see what your saying. I believe I read the section in the manual wrong. I think they meant not to time the first of the 2 notchs BTDC. Your are correct, my cub only has 1 notch.
 
I think you need to go back to the governor to carb linkage adjustment. If I recall, the procedure says to go to 1/2 throttle but I have found ( age of tractor and or condition of the throttle teeth) I have to go past that. I think many members suggest to set it at full throttle. There has to be tension on the spring. If you have adjusted the timing and checked for air leaks around the carb, this is where I would go next.

In my experience, I very rarely have had to adjust anything on the governor itself to get it to run smoothly.
 
Your comments in post 12 are correct. As timing is advanced, the pulley notch will move up, towards the head. With a single notch in line with the pointer, you are timed exactly at TDC. That is where your mark should be at low idle. At fast idle, the notch should move up by more than 1/2 inch, close to 3/4. Turning the adjustment on your timing light to 16 degrees should move the notch back down to the pointer.
 
I agree with the other comments that surging is most likely caused by fuel mixture (vacuum leaks or blockage in the carburetor) or by problems with the linkage from the governor to the carburetor.
 
Jim Becker said:
I agree with the other comments that surging is most likely caused by fuel mixture (vacuum leaks or blockage in the carburetor) or by problems with the linkage from the governor to the carburetor.
Click to expand...
I do as well. I am going to try setting the throttle wide open and adjust it again. I have seen in the manuals they recommended both ways, having the throttle set to half or having the throttle set wide open. I tried half last time, this time I'm going to try wide open.
 
You must log in or register to reply here.
Back
Top