How to tune a carborator? - Looking for an expert to comment

Marty from MN · Sep 19, 2010

Did some searching on the forum and didn't find any good posts on how to correctly tune a carb.

Can one of the experts on this site enlighten me on how to determine how/when to adjust carbs?

Specifically I'm working on a Massey 44 for my FIL, but I assume that the adjustments would be the same for tractors like my Farmall M.

Thanks in advance.

old · Sep 19, 2010

Idle jet you screw all the way in then out 1.5 turns and leave it. Main jet there are a few ways it can be done. One is the screw it out 2 turns and start the engine. Then turn it out till you get black smoke then turn it in till the smoke stops.

John M · Sep 19, 2010

I dont know the tractor, but me, idle screw needs adjusting, not just turned out and left alone. I adjust it until the smoke, while running at idle, stops. Main is set depending on what Im doing, my working tractors get turned 5 turns all the way out, show tractors 2 turns. Again, I dont know the Massey, so 1 & 1/2 turns may be right, but on my Ms it may be close, but I dont just "leave it alone".

CNKS · Sep 19, 2010

If you don't have an operators manual--At wide open throttle and at operating temperature, turn the main jet screw in until the engine stumbles, then out until smooth plus maybe 1/4 turn more. If you do the black smoke thing you may leave it too rich. It needs to be as lean as possible without stumbling under load. If power seems low, you can open it 1/2 turn at a time and see if power goes up. You also need to adjust the low idle the same way as the main jet, except that turning in probably richens the mixture, at least on IH it does, and out leans it. Advance the throttle rapidly--if it stumbles, repeat the process. If you can't get rid of the stumble, the carb needs cleaning. The process I am giving you is in the operators manual for the H and M. You really need an operators manual for your tractor.

rustyfarmall · Sep 20, 2010

It really is next to impossible to describe the procedure in words. The operators manual will come closer to doing that than what anyone could explain here. The absolute best way to learn it is from an experienced, old school mechanic who will give you a "hands on" live demonstration.

Allan in NE · Sep 20, 2010

Gotta remember that these old carbs have two distinct and separate circuits.

Make sure you set the points and the timing FIRST before you start on the carb and do it in that order. Then.........

Adjust the low side speed screw to get the initial idle speed. Clean it up with the low side mixture screw and then finish up by re-adjusting the low side speed as necessary to give you the proper idle.

Adjust the high side mixture as required to "just" give full power at open throttle.

Allan

How to tune a carborator? - Looking for an expert to comment

Marty from MN

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old

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John M

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CNKS

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rustyfarmall

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Allan in NE

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