1951 TO-20

[glenncooner]

Just got the tractor back from mechanic and ran it a few hours-although it seemed to not have power it once had it ran rairly ok for awhile--
now it runs well at idle, but after throttling up and trying to move forward begins to run rough.
---our manuel is specific about the spark plugs-either AC or Champion--Champion plugs, numbers are, 86 com--in the hot range, C7, and the cold range 6M-----AC number is 86Com. ,hot range is 85 com. and cold range is 85com.
not one parts houses have clue what this means.
---We pulled the plugs in it now, one is wet, the others carboned up but dry.
WE are going to check the points, connections ect.
we thought the plugs might play a role in running rough.
any feedback on this would be appreciated.
thanks in advance mg
also the AC numbers

 

[John (UK)]

Check the compression on all cylinders by turning the engine over on the starting handle and seeing if there is a great difference between all four compressions, if there is there is a valve problem or at the worst a problem with rings on that cylinder. You should also check the valve clearances that one hasn't been left slack, especially the cylinder with the wet plug, that requires special attention. The AC plug is AC86, if the plugs are carboned up as you say it may be too much fuel and the Carb mixture needs weakening, but you should smell this in the exhaust and if you open the throttle quickly it will blow black smoke.Check the bearing in the distributor that it isn't worn, turn the distributor until the heel of the points is just coming on the cam, now press the centre shaft towards the points and see if they open, if they do then the bearing is worn and the points are not opening consistently when the engine is running, the gap is varying which would cause erratic running. You could also check that the coil is wired correctly, the power lead from the switch should be attached to the terminal marked + or SW or PWR. If the tractor still has a generator it should be wired with the battery negative to ground, if the ground lead is still attached to the back of the dash panel it should be extended and moved to one of the bolts near to the starter as the Dash Panel is no longer making a good contact with the rest of the tractor after all these years. get the engine hot and then open the throttle quickly, it should open up without any black smoke or spluttering, if it splutters, you should make the mixture slightly richer by unscrewing the main jet 1/8 turn and test again,if it still does it, increase the fuel again until it opens up cleanly. If you get black smoke when you open up the throttle then the mixture is too rich and you should screw the main jet adjuster in 1/8 turn at a time, test it after each adjustment until it will open up cleanly.....John

 

[Jerry/MT]

I would recommend you run Autolite 3116 plugs in your tractor. If you prefer champions, they should be D21's per the Champion website. They are a non-resistor plug which is what your machine should have.
The fact that your plugs have a sooty black deposit on three of them indicates a rich mixture. (If the "wet plug" is black and oily, you've lost oil control or have a bad intake valve seal or a worn valve guide on the cylinder.)
However before you mess with the carb adjustments, check the spark by pulling the center wire out of the distributor cap and holding it about 1/4" away from a good ground, turn on the ignition and attempt to start. You should have FAT, BLUISH-WHITE SPARK, the color of lightning. if it's a spindly blue, red, orangey, or yellowish, it's not good and you'll have to find out why. Poorly set, burned, corroded, or oily points can be the cause,as well as, poor connections, bad condensor, poor coil, worn distributor bushings, bad keyswitch, etc
If you have the requisite FAT, BLUISH-WHITE SPARK, then check your timing and the advance mechanism with a timing light.(You said the the engine ran poorly at higher speed so check the initial timing and the advance.)

If they are fine, go on to adjusting the power jet(the big screw on top of the fuel bowl). Screw it in completely (don't reef it down, just close it!)and count the turns in and record them. Then turn it out 1-1/4 turns. See if that improves the situation. if it does, let the engine warm and then slam accelerate it to max speed. If it doesn't accelerate smoothly, without coughing, enrich in eigth turn increments until it accelerates smoothly.
Do these checks systematically and in the order I have stated them and anytime you change anything start up the engine and check it out before you make another change. This way you will isolate the problem.

 

[glenncooner]

thank you for the help, i will start looking for the rigbht plugs to start with, then proceed onto the the other possible problems if need be.
---three years ago this engine was run out of oil due to a jerry rigged oil pan and plug-it sat in the barn since then. the engine was hand cranked turned over and marvel oil added to the cylnders after this happened.
---now the problem is definite--the tractor wil start and idle steady, but when gear engage it begins to run rough,and now almost comes to a stop. but when idled down will run good again.
probably will haul the tractor to a mechanic --we blew out the fuel line, checked all connections,still dont have correct spark plugs but that will be corrected this week.
thanks again.
mg