SM Carb Help Please

I am having some difficulty in setting the low RPM to 350-400. I initilly set load screw at 3 turns out, air adj and idle screw per service manual. I am using dwell/tack and cannot get the idle rpm below 650 without adjusting load screw to where the engine is not running smoothly. At 3 turns out starts easily but if I turn in 1/2 to 3/4 of turn engine smooths right out and rpm"s increase about 400. The idle screww is fully backed out. Could the governor being out of adjustment cause this? Thanks for any advice.

R/

Pete

Yes. Unless the sdjustment under the little angled cap allows the near closure of the throttle plate, the idle stop screw will not work as designed. Jim

Pete - Good chance it's a governor to carb linkage issue. A couple things to try:

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Loosen (don't remove) the two screws that clamp the throttle shaft tube to the governor riser. Now have an assistant pull upward on the tube while you retighten both screws.

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If that doesn't help, adjust the carb shaft linkage:

- Remove the cover at the top of the governor riser.

- Inside the riser remove the cotter from the pivot pin and remove the pin.

- Set the throttle handle wide open.

- Now turn the carb throttle shaft as far clockwise as it will go, lift the governor connecting rod as far as it will go and try to re-insert the pivot pin.

- If the pin does not slide in easily, loosen the locknut on the connecting rod block and adjust it up or down as required until the pin slides in.

- Finally tighten the locknut, replace the cotter pin and the riser cover.

I think your carb needs cleaning, the idle mixture seems to be the first indication. And the load on a Super H/Super M carb up is set at 5 turns out for max power but can be turned in for lighter loads. I have never tried it, but I doubt if it will pull anything but its own weight at 3 turns out. It is a SM carb if the choke lever is on the inside, If on the outside it is an M carb, and except for the idle adjustment forget what I said.

BEFORE you start turning screws on the carb. you had best start from square one . And make usre that EVERY THING is dead on . First check and make sure that the gov. is working correctly and that the BUSHING on the arms where the Gov. spring are there and that the spring does not FLOP around in big holes as nine out of ten have the bushing missing and you will not FIND them in the parts book . Once the spring is tightened up then ya do the carb to Gov adjustment then ya do a base set like the book says , next step i do is a complete tune up and check the dist. for ware and proper timing advance , once that is correct then lets move on to the valve adjustment and take your time here and watch out for what i call bridgeing where due to ware on the end of the rocker arm where it makes contact to the valve stem as most do not hit dead center on the rocker arm and if your not looking you can and will get a false set as you try and use the whole feeler gauge when you just need to use your feeler gauge off to the side so as not to cause the bridgeing . And you will hear guys say must be set HOT just set the valves to spec.s if everything is warmer then 70degrees as unless your going to WORK the tractor then you will NEVER get it up to OPERATING temp and if you did you sure won't be setting valves with a glowing manifold . So once you have this all done NOW start the tractor and let it warm up for say five to ten min. Open the main jet up to 4 1/2 turns to 5 turns then start to slow the ideal down and work at smoothen it out and keep working the curb ideal screw and the ideal mixture screw down . Just a small tweak at a time . JUST KEEP IN MIND HERE that you are working on and OLD tractor that has had extensive field testing and everything in it is well used. and sometimes you can only do somuch. Now IF you totally rebuilt each and everything then you might get it to be perfect . Cam ware can give you fits dist ware drives ya nuts and a Gov that is wore out is why they make Crown Royal.

I kinda like the white owl whiskey...it has the moonshine look, smell and taste.

FARMALL H & M CARBURETOR & GOVERNOR ADJUSTMENTS

Note: #1, 2, & 3 adjustments are done with the engine not running when the carburetor has been removed & replaced.
1. Loosen the 2 screws that are holding the governor tube to the governor housing. The clamp is slotted to allow adjustment. Tighten the tube-to-carburetor screws; gently tap the tube so it "centers" itself, & then tighten the tube-to-governor screws.
2. Remove the top cover on the governor housing (has the pipe going to the cylinder head) and check governor to carburetor synchronization. Remove the cotter pin so the clevis pin can be removed. With the operator's throttle lever set wide open and rotating the horizontal rod upward to wide open throttle position, the clevis pin should just slip into the rod that is in the tube. This horizontal rod should rotate freely allowing the carburetor throttle plate to move from idle to wide open. Adjust the clevis height if needed & lock the nut. You may need small fingers & right-angle needle nose pliers to make the job easier. Return throttle lever to idle. Re-attach the top cover.
3. Carb adjustment: idle air screw is set at 1½ turn out to start with; high speed mixture screw is 2½ or 3 turns out.
4. With the engine warm & running at wide open throttle (WOT), turn high speed mixture screw (on the bottom facing down to the rear) in until the engine begins to starve for fuel. Then turn the screw out until the engine begins to blubber. Now find the "sweet spot" in between the two settings. If you are working the engine (plowing, etc.), then the high speed screw needs to be turned out ½ turn or more beyond the "sweet spot" to be sure the engine isn't starving for fuel and can develop its rated power.
5. The same procedure can be followed for idle air mixture with the addition of setting the idle stop screw (just to the rear of the governor shaft tube) to adjust the low speed RPM.
On the "H"& “M” carb, the idle air mixture screw (faces to the front just below the idle stop screw) is an air adjusting screw so turning in will richen the mixture and out will lean the mixture.
Repeat the carburetor adjustment procedure again to make sure “all is well”.

If it wasn't for Crown and home made wine these things would drive us all nuts.

This is a Super M carb, it has no "sweet spot". Max power is 5 turns out.

I've found a good single malt scotch is equally as effective.......also quite tasty(!)

I found my Blue Ribbon book on the fuel system and with a slight adjustment of the low speed idle screw inside governor the rpm dropped to 400. Checked hi speed and it is dead on at 1600. increased rpm to 420 with idle adjust screw. All is well! Now as for the Main Jet screw no way can I set that to 5 full turns out. Way to rich and barely stays running. 2 1/2 turns and purrs like a kitten? Carb has been cleaned and rebuilt with Case IH parts. I'll just leave well enough alone. Thanks for the guidance and recommendations on refreshments to get me through the task at hand.

In that case you either have an M carb or a SM carb that has M parts in it. If the choke lever is on the outside it is an M carb, inside it is a SM carb.

SM Carb for sure. The choke is on the inside of carb. The parts used for rebuild were from Case IH dealer?

I think my point is a lot of people don't realize that the M and SM carbs are different, that includes the CaseIH dealer. So I suspect that the parts used in yours were for an M. Not knowing the difference, I cleaned and put the correct kit in my SH, but I did not touch the main jet needle and jet. I adjusted it the way I always adjusted an H. Worked fine until I started up a slight incline with no load -- it wasn't getting enough fuel -- that is when I read the operators manual and found the 5 turns out thing. The SM and SH carbs are also different, but I don't think a correct SM carb will pull anything with the needle 2.5 turns out. The SM I have is undergoing restoration. It came with an M carb. I have a used SM carb for it that has been cleaned and rebuilt, I don't know what the main jet is. If I ever finish the thing I will do some experimenting and adjust it as is correct for an H and M. If it is ok, I will try to find a jet and screw for a SM. As you say 5 turns out with a M main jet is way too rich.

The main jet never comes with a kit and most likely is not available. I had my parts man go through all dealers several years ago just to come up with a couple I needed.

Forgot to add. If you can over fuel by backing the main adj needle out like you say, the main jet has most likely been drilled out which is pretty common practice especially with the use of ethanol added gasoline. Most don't have wire gauge drills so they use a drill much too large.