M-SM carb

CJ_1080 · Apr 16, 2010

Hey all, is the main carb body of a farmall M and a Super M the same? Im sure the venturi and main jet are different, just talking about the main body. Also will the main jets interchange? Thanks, as always!

CNKS · Apr 16, 2010

Main jets and adjusting screws may interchange, I don't know, but the SM carb has a "fixed" jet that has a screw that gives max power and fuel consumption at 5 turns out. All gas carbs from the Super H through the 560 are that way. At 5 turns out the needle is completely out of the jet. You can turn it in for lighter loads and less fuel consumption. M jet is adjusted in until rough, out until smooth, etc. You don't adjust the SM carb that way.

D Slater · Apr 16, 2010

If its the throttle body I think M gas carburetors 50983DB,DC used the same one as SM gas carburetor 356948R91. Earlier M carbs and R92 SM had some small differences. You never know whats in them though, IH made one or two power improvement pakages for the M carbs. I'm thinking 2 passages in the body were pluged when used, or maybe one can't remember for sure, along with other metering parts.
Then there was another kit for fire crater piston kits, IH made a mistake and put the wrong size main seat in some of those kits. They were suposed to be changed out, but Some are still in carburetors or I measured ones somebody drilled. only remember the parts going in the bowl part of carb on them. Also some aftermarket kits were sold that advertized power improvement.
Bowls on M and SM have the choke lever on different sides. most parts can be installed from one carb to the other, how it ends up working depends.

randy hall · Apr 16, 2010

cnks, a fixed jet carburetor has no outside adjustment, about the only way to give them more gas is to raise the fuel level in the bowl. all m super m 400 and 450 carburetors have a main jet adjusting needle.

rustyfarmall · Apr 17, 2010

(quoted from post at 15:55:49 04/16/10) Hey all, is the main carb body of a farmall M and a Super M the same? Im sure the venturi and main jet are different, just talking about the main body. Also will the main jets interchange? Thanks, as always!

The big difference is that the M carburetor has the choke lever on the side AWAY from the engine, and the Super M carb has the choke lever on the inside, right next to the engine. All of the internal parts will interchange.

CNKS · Apr 17, 2010

I know that -- Note that I put "fixed" in brackets for lack of a better word. At 5 turns out you cannot add more fuel, but you can reduce it. At 5 turns, and I believe even 4, the tip of the needle is not in the jet. It apparantly reduces the fuel as it gets closer to the jet. I have a Super H and a 460 with that basic carb. When I rebuilt the one on my Super H, I adjusted it like an H or M carb, in until rough, out until smooth. Started cutting out with nothing more than a slight incline -- then I read the manual.

rustyfarmall · Apr 17, 2010

(quoted from post at 07:18:36 04/17/10) I know that -- Note that I put "fixed" in brackets for lack of a better word. At 5 turns out you cannot add more fuel, but you can reduce it. At 5 turns, and I believe even 4, the tip of the needle is not in the jet. It apparantly reduces the fuel as it gets closer to the jet. I have a Super H and a 460 with that basic carb. When I rebuilt the one on my Super H, I adjusted it like an H or M carb, in until rough, out until smooth. Started cutting out with nothing more than a slight incline -- then I read the manual.

CNKS, that particular screw has NOTHING to do with adjusting the idle. The idle adjustment screw is located ABOVE that one, right next to the idle SPEED adjustment screw.

CNKS · Apr 17, 2010

Rusty, where did I or anyone else mention the idle jet??

M-SM carb

CJ_1080

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CNKS

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D Slater

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randy hall

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rustyfarmall

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CNKS

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rustyfarmall

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CNKS

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