Farmall Cub

I put my rebuilt carb on the '57 about two weeks ago. I opened the idle adjusting screw one turn and had no trouble starting the engine. I finally went out to set the idle this morning.

I have read my manual on this but still don't understand. With the engine warm and throttle set at slow speed...(all the way back), I started to turn the idle adjustment screw in, and kept turning in until it was seated. At this point the tractor idles very nice at 700 rpm, and slowly advances rpm as the throttle is opened. At full gov. rpm (1800?), it runs very well and sounds ready to go. Again, this is with the throttle adj. screw seated. Did I mess up something on the carb rebuild?

If I open the adj. screw one turn, the tractor runs fine too, but the idle speed is too high, or maybe not...Should idle speed be about 700 rmp
or faster.

This engine has 1035 hours on it since it was rebuilt.


Thanks

Mike

Mike,
Is the adjusting screw on the throtle shaft adjusted? This is how I go about it:

I get the engine to op temp. Then I adjust the idle screw so that the engine runs smooth. Then I adjust the throtle stop screw for the proper rpm.
Sometimes I have to re-adjust the governor linkage to get the throtle shaft stopping on the screw.

I should have mentioned the the idle screw end up about 1 1/4 to 1 1/2 turns out.

Thanks Donny.

OK I've got it... With the idle adj screw open 1 and 1/4 turns the tractor will idle down to about 200 rpm and still run smooth, but it sounds happier at 700. What is the recommended idle speed? Is there an overheating problem at too slow an idle speed.

When I begin to open the throttle from idle (700) , the rpms advance smoothly up to 900 rpm, then she snarrels a little and jumps up quickly to 1150 rpm. From there on up to 1800 rpm the engine speed advances slowly and evenly with each click on the throttle. Is this normal or is the governor sticking

mt

PS Do you know where I can get a copt of the TC-37F Parts Manual for the mag

I'm confused, which idle screw you are adjusting, speed or mixture? So you know what screws I'm talking about - the mixture screw is the one going into the throttle casting, the speed screw is between the carb and the engine block on the throttle shaft. If you didn't use the IH kit, some of the off-the-shelf kits have lousy parts that cause more problems than they solve.

If the engine runs with the idle mixture screw seated: you have clogged/blocked idle circuit ports (off the shelf kit bowl gasket will block the intake port), leaking gaskets, warped/cracked castings, bad idle mixture screw (grooves on the beveled part or bent), fuel level in bowl too high, blocked bowl vent (poorly cut bowl gasket will block it) or some combination of gremlins by-passing the idle circuit in the carburetor. Something somewhere is allowing fuel to be sucked out of the bowl to keep the engine running when it should stall due to lack of fuel.

If the idle speed screw won't slow the idle speed down to almost nothing: the throttle butterfly may not be seated correctly on the shaft and has a gap when it should be closed, a non-IH kit throttle shaft assy is too generic for the screw to function properly and tends to be a bad fit for the idle speed adjusting screw, air is leaking around the throttle shaft seals, warped castings, the rod from the governor rockshaft to the throttle is binding somewhere or needs adjusted and keeps the throttle open at idle. Again, it could be several things working in concert to cause the problem.

Since you recently had the carb apart and the engine runs fine, chances are it's a simple adjustment or fix.

The kit was an IH....I had been forwarned about other ones.

The throttle stop screw or speed adjustment screw allowed me to slow the idle down to 200 rpm and still run smooth and quiet with a little lope. The mixture screw was open one turn. Just wanted to see how slow it would run. What is the recommeded idle speed?

With the engine speed adjusted to 700 rpm and the mixture screw open one turn, i closed the mixture off all the way...seated the screw. The rpms dropped down to 200 again, the engine loped..not happy. but kept running. I didn't want to run too long at the slow speed, but it ran for about a minute brfore I opened it up the mixture to one full turn again. The idle went back to 700 rpm.

When I begin to open the throttle from idle (700) , the rpms advance smoothly up to 900 rpm, then she snarrels a little and jumps up quickly to 1150 rpm. From there on up to 1800 rpm the engine speed advances slowly and evenly with each click on the throttle. Is this normal or is the governor sticking

I guess I should be happy..it starts easy, DOES NOT LEAK, and runs fine.


Thanks

Mike

Mike,
I missed part of your first post. Sorry
Carl is right in what he said but, if the throtle butterfly is open and the idle adjusting screw ( the one on the throtle body) screwed in the tractor will run however very rough. With the butterfly closed and the idle screw all the way in the tractor will die for lack of fuel. I sounds like you have it pretty good now.

Mike wrote:

When I begin to open the throttle from idle (700) , the rpms advance smoothly up to 900 rpm, then she snarrels a little and jumps up quickly to 1150 rpm. From there on up to 1800 rpm the engine speed advances slowly and evenly with each click on the throttle.

It sounds like the governor or the linkage is binding

Mike:

Also, as it seems to keep getting skipped, the answer to your idle question is between 450 and 600 rpm at low idle according to the manual if I remember correctly.

Ellie likes it around the high end of 475 to 550 rpm. After that she gets a little racy.

Thanks Donny, Lurker Carl and Rudi.

I guess the idle speed is whatever the tractor likes best, 450 is too slow for this one. Its runnin great now

Ordered another kit from c and g today, and will do another carb soon...with stripped threads. I was reading Lurker Carl's fixes for stripped threads, would one of those Helicoils work on the IH carb or would you guys recommend proceeding with the JB Weld treatment.

Thanks

Mike

Mike,

Which threads are stripped

the fuel line fitting.

Mike,

That's a 1/2-20 thread. A heli-coil will work but I have found the finer the threads the more difficult it is to use an insert. It would also be hard to break off the tang with the screen in there. I think I'd go for the J-B Weld.

I was hoping you wouldn't be sayin that, and that the helicoil would be quick and easy.

The JB Weld treatment seems pretty tedious, but if it will hold up and is easier that's what I will try. Never have done a helicoil either, but they seem cool

Guess I will have to get a box of those q tips.

Thanks Donny.and ..Do you know where I can get a copy of the TC-37F Parts Manual for the mag

Mike:

The TC-37F is on the server. You can get a copy for yourself from Binder Books.

I have that one...Now I know what its called TC-37-F. I thought Donny had another manual just about the mag.

Thank you Rudi



Mike