Could your hydraulic system be loading the engine causing the drag?
Is the starter new?
Try connecting jumper cables from you 12 volt battery straight to the starter as a bypass test.
The governor has springs in it that will push against the throttle, nothing that could bend linkage though.
How is the engine oil pressure?
If you have a lever that sticks and has to be centered by hand to prevent unwanted movement, it could add load to the engine when cranking.
The torque convertor, if it has damage, could load the engine too. I don't think you said anything about transmission trouble so, I doubt this is your problem.
I always try to go to the basics first. I would have a real heavy load test done to the battery. If you can get an clamp-on type amp-meter. Test the cranking load through the cables. Then I would have the starter tested. Find a shop people trust, too many just sale parts.
The wear you saw on the cylinder walls, did it look like a piston could be seizing? I have replaced several 3204 engines due to wrist pin failure and seizure of the #4 piston.
I am concerned about the water leak. Did you notice any of the pistons that looked clean? They should be black from soot build-up.
Does the engine spin easy by hand?
The engine problems I repaired were mostly from overheating. Radiator, fan belts and water pumps were the root cause. This high heat would cause the piston to start seizing in the bore. This drag would add wear to the wrist pin bearing and it would cause it to wear out early. It happens to #4 because it is the furthest from the water pump. You would get a light knock that is most pronounced when the engine is decelerating. It will change its sound when the fuel line is loosened to "cutout" the cylinder.
The head gasket failure is common on this engine too. Heat again was the cause.
The transmission transferring oil with the bevel gear case likely happen when the machine worked up hill one day and down hill on the other. It has a seal in the rear of the transmission but, a rebuild is needed to access it.
The steering lines would not work if something was crossed. The most common failure on these tractors is the valve control bearings wear out and don't release the steering clutch correctly. You will have to force a turn to get it to do anything.
Just turn the drive shaft by hand, it should turn with some effort but, not need a bar to do this. Normally it can be done by hand but, not always. After it first moves it should turn a little easier. If you must force it, then you may have a problem.
There are far too many issues to get into now about testing convertors. BotXXXXX XXXXXne is it still should start fine if the shaft turns easy and most problems are overheating the oil.
Be sure to double check the starting system, I have skipped over this simple stuff before and it always came back to bite me.
You should be able to remove the injectors and have the starter spin the engine easily.
I hope this is being helpful, let me know if I may be going in the wrong direction.
Will I have to disconnect the drive shaft from the bevel gear? The injectors are PC type. How do I go about releasing the pressure in the combustion chambers to make sure the engine is spinning freely?Would a worn wrist pin cause the engine to turn over hard?
Sorry, I was thinking your tractor was of the later design were the transmission was attached to the bevel gear. Removing the driveshaft will not help much on your model.
The PC type injectors only need the fuel line and then the body nut removed to pull the injector. To install the injector, tighten nut to 100 ft-lbs.
The wrist pin would not cause the dragging. The scarred walls from the piston flopping in the bore will cause the dragging.
Please send me your serial number so I won't be guessing about the model tractor you have.
I doubt small scarring will cause trouble other than burning oil. If it has heavy wear this will cause more wear on the piston and as soon as the engine warms-up, it will bind. Cold probably won't bind the engine.
Pulling the injectors is the easiest way to check how the engine will spin free.
The torque is only 55ft-lbs and tool required is a 5P0144, I don't remember it being a special socket but, I have only done one PC engine like this one.
Did the starter test ok?
Here is a picture of the lines group. It may help.
Here is an operations drawing for the steering system.
VIEW OF STEERING AND BRAKE SYSTEM IN STRAIGHT FORWARD 1. Stem. 2. Spring. 3. Spool. 4. Oil Line. 5. Steering valve. 6. Steering pedal (for left turn). 7. Brake pedal. 8. Steering pedal (for right turn). 9. Oil line. 10. Oil line. 11. Transmission. 12. Adjustment bolt. 13. Hydraulic piston. 14. Yoke. 15. Steering clutch.
This view shows the machine in the STRAIGHT FORWARD position. The pressure oil in the line (10) from the transmission is stopped at the steering valve (5). Oil from the hydraulic piston (13) goes through line (4) to the steering valve (5), to the reservoir of the transmission through line (9).
I hope this is what you are asking . Let me know if you need more.