Farmall M Carburator
Posted 17 April 2009 - 05:10 AM
Does anyone know the base setting on a M carb. Thanks Scott
Idle mixture screw 1 1/2 turns out. Load adjustment screw 3 turns out.
I'm working on a 400 and was wondering about the settings. Which is the load setting screw? She used to never idle low enough until I fixed the slop in the throttle linkage and pushed down the governor shaft tube. However the uppermost screw, I'm assuming the idle screw, doesn't respond unless you tighten it. Is the pin/buttlerfly worn out? I'm tempted to put an overhaul kit in it.
Posted 17 April 2009 - 07:25 AM
A good carb kit would be money well spent...
Member IHCC Chapter 37 & 42 North Carolina
1951 Farmall "M"
1949 Farmall Cub - Original "Blue Ribbon Reconditioned"
1934 Farmall F-12
1929 Farmall Regular
1956 Ford 640
1967 John Deere 112H
1973 John Deere 140 H3
1985 John Deere 420
1999 F350 6.8L V10 DRW 4X4 Supercrew XLT Lariat
Posted 18 April 2009 - 01:20 AM
Be sure to get a good quality kit that is complete. I have had bad luck with the Tractor Supply kits. You should get a throttle shaft and choke shaft in the kit, along with the bushings that the shafts ride in. Belive it or not air can get sucked by the shafts effecting the mixture and make the engine run poorly.
Posted 21 April 2009 - 05:08 AM
Posted 21 April 2009 - 05:58 AM
3 turns out and 1 1/2 turns out...from all the way in right? I'm a little leery of doing that because a mechanic said to be careful with older stuff. I've noticed every now and then the carb will leak a little gas after running the engine for a few minutes. It also seems when I was mowing last summer she was burning alot more gas than normal. Yes, a carb kit is in order. One website is selling a kit for $19. Too good to be true?
Those are good starting points. epending on the load you are going to be turning 3 turns on the load screw may be a little lean. I usually set mine at 4 turns. After running the tractor underload for a while pull a sparkplug & see what it looks like. If black & sooty turn the load screw in 1/2 - 1 turn, if whitesh gray turn it out 1/2 turn or so.
Adjust the idle screw to where you want the engine to idle. I set mine to idle fairly slow, can't tell you where, it's just an "ear" thing. After setting the idle there is another screw to the right of the idle adjustment screw. It's an air screw & needs to be set so the tractor idles smoothly.. Usually a quarter turn one way or the other after getting your engine idle set will do it.
As for running the adjustment screws in, that's the only way where your going to have a known starting point & is the way the book calls to do it. Just don't go tightening the adjustment screws down tight with force whn bottoming them out against their seats. Turn them in till you feel them just start to contact the seat then turn out from there.
$19 for a carb kit is about as low priced as I have seen. Last one I bought was arund $25. I usually buy a "Tisco" repair kit at my CIH dealer. First thing I do after buying the Tisco is to throw their needle valve away & buy a CIH one. Every aftermarket needle valve I have boughten wants to stick. Don't have near the problems with the CIH ones. I wish they wuld come back out with the ones with the steel tips like they originally had instead of the rubber tip. BTW, you can buy a carb kit from CIH but the last time I checked it was over $100 However, it does have a lot more pieces than the aftermarket kits but the aftermarkets usually will have the basics that you need.
IH tractors currently owned: '49 M, '53 stage 1 L-SM, '53 stage 2 L-SM, '54 SMTA, '66 806D w 2355 loader, co-own a '66 1206 with IHboog, store a '66 706 German for IHboog. IH / CIH equipmemt - '11 MX 275, '10 STX 435, '03 MX255, '12 7120 combine w/ 40' 2162 draper & 3208 ch, '07 3310 sprayer, '12 1250 16x30" planter, 34' 330 True Tandem , 18' 870 , 7x16" 720 on-land plow, 6x18" 720 in-furrow plow, , #60 4X16" Plow, #1300 3 pt 9' sickle bar mower
Posted 22 April 2009 - 05:44 AM
Looks like I have some adjustments in order.