Cub throttle issue

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jsfarmall
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Cub throttle issue

Postby jsfarmall » Mon Jul 03, 2017 8:54 pm

On my new rebuild, engine runs good, purrs like a kitten but I don't have much rpm when thottle is wide open. Idles down great though. When full thottle I can push the governor rod and get more rpm. When I let go of it rpm backs down to where is was. I'm.only getting maybe have rpm.

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Re: Cub throttle issue

Postby Jim Becker » Mon Jul 03, 2017 9:54 pm

Did you readjust the governor to carb linkage when you put things back on?

jsfarmall
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Re: Cub throttle issue

Postby jsfarmall » Tue Jul 04, 2017 7:01 am

I did. It feels like I'm running out of travel like the carb is.maxing out.

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Re: Cub throttle issue

Postby inairam » Tue Jul 04, 2017 8:59 am

Did you do any work to the governor like replace or not replace the spring throttle lever arm? Did you replace a long lever with a short one or anything like that? are you sure the lever is moving freely?

Did you check the adjustment screw on the carb is restricting the range? or if the cotter pin for the choke is too long and hanging up somehow?
When you only have 9 horsepower you need to know the names of all of the ponies!

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Re: Cub throttle issue

Postby Scrivet » Tue Jul 04, 2017 9:10 am

How are you determining "maybe half rpm"? By ear? Ouija board? You need a tachometer either electrical or hand held mechanical. A handheld one can be placed on the PTO shaft with it engaged since it is running at engine speed. It is very easy to guess wrong on what the actual RPM's are. Once you know what the RPM's are, then take a slow read through the carb linkage adjustment procedure like you have never done it before. Most throttle issues are caused by linkage problems. Most of those are carb to cross shaft, cross shaft binding, or cross shaft end worn/sloppy going into governor spring. Always suspect the most common causes and eliminate them first.

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Re: Cub throttle issue

Postby Jim in SC » Wed Jul 05, 2017 6:10 am

When I got my Cub (a 1951), the governor was frozen. The engine ran similar to what you describe - not much in the way of acceleration. When I did my rebuild, I began soaking the governor with penetrating oil just about daily for a couple of weeks. I also began (gently) rotating the arm on the governor that attaches to the rod that leads to the carb. Eventually, I removed a bolt on the governor and sprayed penetrating oil directly into the governor. This freed up the governor and the Cub now runs fine. I suppose that removing the governor and disassembling and cleaning it would be preferable, but that was a last resort for me. I'm glad I didn't have to do it. There are some great threads on this forum that will show you how to disassemble your governor if you decide to go that route. Here's one: http://www.farmallcub.com/phpBB2/viewto ... 11&t=44139
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Re: Cub throttle issue

Postby Crimson Tim » Wed Jul 05, 2017 8:46 am

Also, I'm sure you know this already, but just in case: the Cub engine RPM (1600 or 1800 for the later ones) is only about half of what most modern equipment runs (3600).

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Re: Cub throttle issue

Postby jsfarmall » Wed Jul 05, 2017 10:04 am

I was estimating by ear. I got another cub and could tell the one I'm working on was nowhere near what my other one runs. I believe my governor spring may be a little week and there is a good bit of wear in the holes the spring hooks to. I made some adjustments to the governor and throttle rod and got things better. Close enough can't tell much by ear.

Where can I pick up a tach for testing purposes?

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Don McCombs
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Re: Cub throttle issue

Postby Don McCombs » Wed Jul 05, 2017 1:59 pm

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Bob McCarty
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Re: Cub throttle issue

Postby Bob McCarty » Wed Jul 05, 2017 2:39 pm

Some auto parts stores will loan tools but I don't know what you have locally. If you get a SW like Don shows above, NAPA carries replacement rubber tips (or used to).
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we need to think differently."
-Albert Einstein


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