Friends grandpas tractor, again.

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LRiddle
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Friends grandpas tractor, again.

Postby LRiddle » Tue Jul 25, 2017 4:24 pm

Ok, I got this tractor running smooth now, but the problem is that I cannot throttle up fast. On my tractor I can go right from low to high idle, if I try that with this one it will die. If i take my time and bring it up slowly, I can get to high idle and it runs fine. This has me thinking one of two things.
1, Everything is fine and this is just this tractors "personality." Or
2, The carb is still not completely clean and the fuel isn't in the bowl to take it up that fast and I have to wait for the fuel to "catch up" before going higher.

Some background, 1951 Cub, Ih carb, all new fuel line, fresh premium rebuild kit from McDonald carb and the mixture screw wants to be set to about 1/2 turn instead of the 1 1/2 I've read about. Also seems to like the choke a bit more than my tractor, which makes me think it's a fuel supply issue. But as I said, with only my tractor to compare it to, I'm not sure if it's just how this one likes to run. I have put my carb on it and it starts and runs just like my cub, with very little choke. I'm leaning towards more carb work, but I'd like your guys' opinons first. Thanks.

Edit: Forgot to mention that I can throttle up faster once it is warmed up.
Last edited by LRiddle on Tue Jul 25, 2017 4:36 pm, edited 1 time in total.
Luke Riddle
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birddog
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Re: Friends grandpas tractor, again.

Postby birddog » Tue Jul 25, 2017 4:32 pm

I haven't done much adjusting on my Cub carb. but on LGT engines that problem is generally caused by the low idle and high idle (full throttle) not in tune to one and another. It could also be low fuel in the bowl as you suspect or some blockage internally.
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Re: Friends grandpas tractor, again.

Postby Bob McCarty » Tue Jul 25, 2017 4:38 pm

Did you set the float height and drop when you did the rebuild?
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Re: Friends grandpas tractor, again.

Postby staninlowerAL » Tue Jul 25, 2017 4:46 pm

Two things to consider: (1) changing the carb from your tractor to the "problem " tractor changes the symptoms, conclusion there is a carb issue. Could be one or more of several things. Fuel flow volume, screen in carb inlet, float adjustment, restriction in the jets. (2) Since the jets are "fixed" (no adjustment) there is some contamination that needs cleaning. Have you cleaned the main met?

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Re: Friends grandpas tractor, again.

Postby Glen » Tue Jul 25, 2017 4:46 pm

Hi,
It sounds like it is running too lean, but it could be the particular carb.
When the carb was apart, did you blow out all the passages with air, if it was sitting for a long time, goop can form in the passages, made by old gas going bad in it. Also dirt settles in the bottom of the carb, in the little passages. Wear safety glasses when using the air.
If a passage is plugged, you might need a wire pushed in it to open it.
The owner's manual says start at 1 turn open when adjusting the idle mixture screw, I have found that they usually need to be open more than 1 turn, but it could need less than a turn.
It says to have the engine fully warmed up when making the final adjustment. :)

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Re: Friends grandpas tractor, again.

Postby Jim Becker » Tue Jul 25, 2017 4:52 pm

I suggest next step checking the actual fuel level in the carb bowl. Replace the drain plug with a pipe nipple and put a short length of clear plastic tube on the other end. Bend the tube up so it reaches above the carb. Turn the gas on and see where the level shows in the tube. It should be between 9/16 and 5/8 below the top of the bowl gasket. See what happens to the level when you start it and when it stumbles as you speed the engine. You may need to raise the level a little. After checking this, open the carb up, blow out the passages and readjust the float level if needed.

The pipe nipple is 1/8. It and the tube should be available in any hardware store.

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Re: Friends grandpas tractor, again.

Postby Rick Spivey » Tue Jul 25, 2017 5:50 pm

If everything else is correct, then the "stumble" you have when throttling up can usually be adjusted out using the mixture screw. That screw controls air, not fuel, so in means more rich, out means more lean. rather than listening to the idle (only), I use the fast throttle technique to get the mixture as best I can. All tractors of this vintage run a bit rich, so don't let that cause you to turn it out too lean. I will also say that I doubt yours is just the mixture screw, it sounds like you may have other obstructions in the fuel flow.
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Re: Friends grandpas tractor, again.

Postby ntrenn » Wed Jul 26, 2017 11:31 am

Sounds lean to me too....i would look closely at the main jet...a very thin layer of grime will be noticeable in engine power. Use a telephone wire to clean them...

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LRiddle
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1951 Farmall Cub - Chesty

Woods 59 belly mower

54A blade

1956 Gravely L

Dozer blade

Tiller

Rotary Plow
Circle of Safety: Y
Location: Tallmadge, OH

Re: Friends grandpas tractor, again.

Postby LRiddle » Thu Jul 27, 2017 10:52 pm

Lot's of good ideas, thanks for the input. I didn't set float height myself since I wasn't the one to rebuild the carb. I tried to get them to let me take it to the tug, but they wanted to try a $44 rebuild kit first. He "has a buddy that's real good with engines". Whatever, not my tractor, so it is what it is. I guess I'll try Jim's idea of running clear tube out of the bowl to check level and tinkering with the adjustment more. I really don't want to open the thing up if I don't have to. I already tried to get it fixed up nice and I'd hate to have to say "I told you so".
Luke Riddle
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