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Another carb adjustment question

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BigTone

Member
I put a carb kit in my M, adjusted the float and she runs real good...I adjusted the idle screw like the manual said but when I put the tractor to full throttle and tried to adjust the jet the tractor didnt really do anything? I went the three turns out then followed the manuel but it didnt die down enough for me adjust, should I just keep unscrewing it until does something? Im also getting grey smoke at full throttle, its not a ton but it is throwing some smoke, how should I adjust this?

Thanks for the help, this is the first time i have ever worked/adjusted a carburetor...
 
The grey smoke is the rich condition indicated in my former post. Turn it in till the grey goes away and you are good. between 3 and 4 turns is good. The book is designed around much different fuel. Don"t wory. Jim
 
Which jet do you mean? The main jet screw is turned in at full throttle until it stutters, then out until smooth. If it does nothing it is still plugged. Same thing for the idle jet at 600 rpm or so. I have never had the desire to turn out the main jet until it smokes, you want a lean condition, not rich, that is why you turn it IN first and then out until it is smooth, no more than 1/4-1/2 turn after that. This is all in the Operators Manual, which you obviously need. One other thing. The M carb has the choke lever and rod on the outside of the carb, the SM on the inside. If you have an SM carb, forget the main jet adjustment and turn it out 4-5 turns. The SM idle jet is adjusted the same as the M jet.
 
one thing I'd add to the other advice is once you do as they say - drive it up a steep incline before you put your screw driver away.

You want to test it under some load. If it starts sputtering, back it out a little more, but at that point - go in small increments till it's right.
 
Were you trying to adjust the idle jet at full throttle? The idle jet only meters fuel for idling conditions, ergo "idle jet" . Fiddling with that at full throttle is counterproductive. Go back and set the "idle jet" at idle, and then the load (main) jet at higher and load conditions.
Which manual are you using?
 
Just realize, all gasoline the engine burns goes through the main jet on that carburetor. No other way for fuel to get to the idle circuit at low speeds or main nozzle at higher speeds. So, if you turn the main adjusting screw all the way in and it does not kill the engine that means the needle is not going into the main jet and closing it off. There are different length needles that came with power inprovement packages and the fire crater package had a different taper on the jet and needle so now days there are all sorts of combinations out there. Just turn main needle in with engine warmed up, full throttle until it starts to lean out and back it out about half turn for starting point. Also, many M's have a calibrated main jet just like later models so turning it out twenty turns will not increase fuel flow above what about 4 turns will.
 
(quoted from post at 17:29:02 07/21/12) I put a carb kit in my M, adjusted the float and she runs real good...I adjusted the idle screw like the manual said but when I put the tractor to full throttle and tried to adjust the jet the tractor didnt really do anything? I went the three turns out then followed the manuel but it didnt die down enough for me adjust, should I just keep unscrewing it until does something? Im also getting grey smoke at full throttle, its not a ton but it is throwing some smoke, how should I adjust this?

Thanks for the help, this is the first time i have ever worked/adjusted a carburetor...
Click to expand...

Set it at 3 turns out and then leave it alone. Only reason to turn it out any further is if the engine begins stumbling and missing under a FULL load, and I mean A FULL LOAD, like pulling a plow that is too big for the tractor.
 
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