Almost too embarassed to post again TSX 706

One more time!

Greetings to all! Hope you've been having happy holidays! You may recall that a while back I posted about my MS TSX 706 on my 57 850 and questions about the seats etc. I have been working on this carb off and on since. I have been able to adjust the carb so that it runs fairly smoothly, smokes black smoke only upon acceleration then only light smoke, not much, but you know its there. The tractor runs fairly well, but when I pull the plugs they are sooted up pretty bad. Not oily, but black soot. As a reminder the engine has been rebuilt to include a valve job. Carb rebuilt too. I installed a Petronix ignition kit and Flame Thrower coil. Obtained immediate start up, which in reality was only marginally better that when stock. My rational was that a hotter spark would burn the fuel more completely. It may have, but the plugs were still black with soot. Yes, they were cleaned before the electronic ignition was installed. In searching for answers I found what is called Colortune which enables you to see the combustion as it happens. It is a spark plug device with a glass insert through the plug. Following the directions, when a carb is adjusted correctly you should see blue flame. I see blue flame while at idle. However upon acceleration the flame turns yellow which indicates too much fuel. Yellow flame is expected initially but is supposed to change to blue if the carb is adjusted properly. I was not able to achieve a blue flame at higher rpms. I checked all the recommended areas suggested by the manufacturer, no vacuum leaks. I contacted the Colortune company and they could only suggest the main jet was too large. I am going to take the carb apart again and examine each part. One thing have noticed is that the float spring from the rebuilt kit is different than the original. The original used a small coil spring, the rebuilt kit uses the type that clips on to the needle. I am considering putting all the old parts back in to see how that works. I am running out of ideas and am now thinking the carb is just no good and need to buy a new one. One thing I have considered is the precision by which the MS carb operates. I do not think it is that precise and perhaps I am expecting too much from it and that it will never produce a yellow flame at high rpm. I am looking for any suggestions. I have looked at the Zenith carbs and understand many are very happy with them, but rebuilt kits are also non-existent. Any feedback on the Zenith carb would be appreciated. I want to thank again all those who tried to help previously and perhaps have thought of something new. I apologize for the long post. Hope you have a wonderful week. Thank you in advance.

Help us a little. If an engine is running fast, but not loaded, the carb will br just maybe 1.4 to 1/3 of the way open. This is not using the main jet fully because it is High Idle, not under load. Loaded, it may be OK. it is difficult on crude carbs to get that setting adjusted because it usually doesn't run there. They were made to work hard. Jim

Glen, I think this quote hits it dead center ''I do not think it is that precise and perhaps I am expecting too much from it''. And Jim explains it well. You are expecting a precision engine, running optimally at all rpm's, when in fact you have a tractor engine designed to run rich so it has a lot of power when lugged down. Running them hard gets you the heat and strain it takes to cleanly burn that extra fuel that is turning to soot under no load. Watch just one pulling video, and the light bulb will come on. Where are you in Idaho? I'm up in the northern part of the Panhandle. steve

Here is the deal. Are you finding that when you adjust the main jet to the point it eliminates the smoke once the engine is up to speed or traveling down a level road you now have a stumble when you open the throttle quickly? If so it is just the curse of a tractor carburetor with NO accelerator pump, a fairly long up draft intake manifold runner and the intake manifold that has less inherent heat then say a V8 where the manifold sets right on top of the engine. It has been my finding that IN SOME CASES if you want your plugs to burn clean you have to lean the main jet down and live with a bit of stumble. It can help to set your ignition timing advanced to the point that you are starting to hear some ..pinging.. or pre-detonation when the tractor is up to full operating temps and is under a fair load like going up a steep hill in road gear, then back it off 2 or 3 degrees. Which does bring us to some other points. Does it have a thermostat in it and is the engine coming up to the proper temp? What are you doing with the tractor during the test or run period? If you are only putting around a bit or taking it down the road a half mile you are not really giving it any kind of a test. As Stevie and Jim are pointing out these tractors were designed to be worked and not necessarily make the most economical use of the fuel. One last thing, do you or have you been taught that a machine with a manual choke should be ..warmed up.. a minute or two with some amount of choke applied say a 1/4 to a third? I am used to Farmalls and unless extremely cold they need no choke to run after 15 to 20 seconds. Only if you start them and almost immediately put them in gear and try to move then yes, a quick out and back in of the choke rod will keep it going. If your tractor can stay running at a 1/4 throttle with no choke during a minute or two warm up than DO NOT USE IT.

If you can leave it be and go work the bag off it for a day or 2 not just putter around but work it like go plow with it or other heavy work then come back and look at it. If it cleans up you will have found your answer to rich for putter work and right for hard work.

I replied to your post on the Ford board.

Good morning! Thank you for all your replies! It appears I have been expecting too much out of this carb. I'm going to go through the carb to make sure the jet is the right size, readjust and let it be. Thanks again for you time and replies.

You seem to be under a very basic misunderstanding. Unless you have your carburetor control rods changed around somehow you are not operating the throttle, the governor operates the throttle. You are only setting the idle. You have to put a load on it to get the governor to open the throttle to run where your color tune will show blue. You should go back to your operator's manual and go through the governor linkage adjustment that you will find there.

Thank you! I will do that.

If the main jet is adjustable, try turning it in a quarter turn at a time, then look at the flame and test the throttle response after each adjustment. If it is adjustable there is no need to change the jet.

As said, the only real test is to actually put the engine under load long enough to get a good feel for adjusting the main jet. You'll hear it when it's right. And just because you get it right once doesn't mean it will be right next time, that's why they had adjustable main jets!

As for the black plugs, they will turn black if idled around and never put under load. If this is a hard working tractor, they will clean up if the mixture is right. If it gets minimal load, short runs, lots of idling, try going up on the plug heat range.

MS carbs are good, simple carbs. Simple is better on something like a tractor that sees a lot of dirt, or does a lot of sitting unused. That's why they are designed as they are, simple and few moving parts. Ford tried using Holley carbs for a while, complex with lots of internal moving parts, but would get the mixture closer to right across the power range. Good theory, but they were near impossible to tune and keep working properly. Don't even consider going there!

PS: Forgot to mention, double check your float level, and check the float for gas in one of the pontoons.

High float level will cause rich mixture.

Just the facts .... It's a tractor!! Never designed to be a sports car or to win at Indy or Talladega. It's probably working just fine.. if you want precision buy a sporty car.

If you operate with 10 or 15% ethanol fuel it will lean the mixture. Jim

Check your air filter.

Done! It's okay. Thanks

I always use leaded fuel, never ethenol.

(quoted from post at 23:04:24 12/17/23) I always use leaded fuel, never ethenol.

Click to expand...

t $20/gallon!? Bet you meant to type 'non-ethanol'.........blame the fingers.