Setting high idle RPMs

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J3 Driver
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Setting high idle RPMs

Postby J3 Driver » Sat Jun 23, 2018 9:22 pm

Tonight I was verifying the low idle RPMs in th cub and decided to check the high to. According to the manual I should be seeing 2000 RPMs at full throttle with no load. Is my thinking correct on this?

The first time I got 1600.
CFFA5DEE-F2E4-43B3-A07B-4C9BFBEA6016.jpeg


The second time I got 1800.
91BD42B2-3D4A-4E5C-B288-979209691256.jpeg


So it looks like I need to adjust the high speed screw on the governor. Would you guys mess with it or let it as is. Askonif I do speed it up some is there a rule of thumb about how big a turn equals how many RPMS.

Also as I move the throttle to high RPMs there is a lot of spring resistance. As it it’s hard to get it the hole way up and it really doesn’t like staying there. Will adjusting the governor make this better.

Thanks in advance.

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John *.?-!.* cub owner
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Re: Setting high idle RPMs

Postby John *.?-!.* cub owner » Sat Jun 23, 2018 10:15 pm

I believe a 57 cub would have still been 1800 rpm, I thought they went to 200 rpm in the mid 60s or so, but some of the more knowledgeable people on here will have the correct info.
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Re: Setting high idle RPMs

Postby Eugene » Sun Jun 24, 2018 7:42 am

The engine's high idle appears on the tractors serial number plate.

Depending on which carb carburetor is installed on the tractor, there is a screw on the carburetor limiting the high idle. If you want more rpms, back the screw out.
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Re: Setting high idle RPMs

Postby Waif » Sun Jun 24, 2018 9:56 am

Not sure why your throttle don't like staying "up there". Are the teeth 's integrity on the throttle good? There is a spring for tension too.

In the manual(s) , setting the carb to governor linkage is covered at carb install time.
I check that setting before messing with idle screw at carb..
This last tractor ...A previous owner had cranked up to a scream.
Throttle range was about an inch and a half between a very high idle (at lowest throttle setting) and a "Yikes!"full throttle only a few teeth ahead....

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John *.?-!.* cub owner
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Re: Setting high idle RPMs

Postby John *.?-!.* cub owner » Sun Jun 24, 2018 1:08 pm

Waif wrote:..........
Throttle range was about an inch and a half between a very high idle (at lowest throttle setting) and a "Yikes!"full throttle only a few teeth ahead....
It may have a governor from a number series. They had lighter weights for higher rpms, and also since they were primarily mowing tractors and had only a limited throttle range between the two. I rebuilt one of my cubs and since I was going to one of the cub tugs soon afterward I put a governor from a numbered cub on it, and only had about 4 or 5 teethe between idle and full speed. When I got back from the tug, I took that governor off and sold it then reinstalled the original governor so I had better control of the in between range.
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Re: Setting high idle RPMs

Postby Waif » Sun Jun 24, 2018 1:23 pm

John *.?-!.* cub owner wrote:
Waif wrote:..........
Throttle range was about an inch and a half between a very high idle (at lowest throttle setting) and a "Yikes!"full throttle only a few teeth ahead....
It may have a governor from a number series. They had lighter weights for higher rpms, and also since they were primarily mowing tractors and had only a limited throttle range between the two. I rebuilt one of my cubs and since I was going to one of the cub tugs soon afterward I put a governor from a numbered cub on it, and only had about 4 or 5 teethe between idle and full speed. When I got back from the tug, I took that governor off and sold it then reinstalled the original governor so I had better control of the in between range.


It tamed right down with adjustment ,but I'll look closer at it.
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Glen
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Re: Setting high idle RPMs

Postby Glen » Sun Jun 24, 2018 4:27 pm

Hi,
You can increase the high speed RPM's if you want, but if 1800 is fast enough for you, it's not really necessary to speed it up.
The maximum RPM was on the serial number plate from 1947 - 1955.
1956 and later Cubs have no maximum RPM on the plate.

Raymond Durban's database says at Cub serial number 192113, which was late 1955, the engine RPM was increased. It doesn't say to what RPM. It was 1800 RPM before that.
There were other changes at that serial number also.

Below is a specification page from the 12/20/55 Cub owner's manual showing the engine speeds. It shows the high speed as being 2016 RPM.

http://farmallcub.com/rudi_cub/www.clea ... e%2077.jpg

You could oil the throttle linkage, and see if it frees up some. Oil where the cotter key is in the pic below, the arm commonly gets tight on the shaft there. You can look in from the left side, by the fan, with a light to see it.
You can also oil the other end of the arm pivot, it is right near the high speed limit bolt. :)
Attachments
Cub gov 4.jpg


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