Possibly these pictures are of assistance, from the Harry Ferguson parts book / service manual:
My TEA-20 stated running like it had a bad case of Malaria / Bubonic plaque under load:
After considerable investigation, it was noted (using a STROBE /TIMING LIGHT) the entire distributor required servicing. The mechanical advance was faulty as well as the bearings within the distributor housing.
As I progressed through the investigation it was discovered that the timing chain and sprockets were totally thrashed:
The condition you describe can be caused by many faulty condition's. ie. lack of fuel, lack of air, lack of spark at correct time etc,etc,
Remove the Distributor Cap. Place a socket on the BOLT that hold the pulley in place on the crankshaft. Rotate the crankshaft both CCW and then CW noting ( take a guess) how many degrees you must turn the crankshaft before the distributor shaft starts to move:
Bob....Owner of various colored Tractors as well as a daily user "TEA-20":