Hi Team,
a too lean of a fuel mixture can be caused by the right angle tin lever in the carby main jet system--this causes a requirement of needing choke to run at full speed and load.
The lever gets bent when too much force is used in the initial setting of the main jet for a first run approximate jet opening.
Be aware that this lever reverses the actions of the main jet mixture screw--in for richer --out for leaner.

Because of the flimsiness of said lever it is very difficult to discern when the main jet screw tops out the main jet at its fully raised opened position--miss the subtle change in screw torque to turn it will result in bending the lever beyond the 90 degrees it should be when in service--this then does not open the main jet sufficiently to get anywhere near enough a correct rich mixture for the engine to run effectively with power and not overheat.
Pictures below should explain clearer than I.

Hope this helps.
Cheers,
Eddie B.

If the pony is getting that hot in a minute or so to burn the paint it cannot have a drop of water in the pony. The coolant circulation must be complete blocked or an air lock. The timing needs to be checked like Neil said by going through all four cycles and checking valve positions and rotor position for intake, compression, power and exhaust. When that is correct the overheating can be checked.

maybe its my eyesight failing...but do those sparkplugs look very different from each other? one of them the porcelain is light coloured (should be tan or brown) and the other one looks much darker, almost black...(oil or too much fuel)? they look to have some time on them as well...

-another picture(s) of the plugs side by side would be great...with a white background...just so everything is more visible..

-better yet...a fresh set of plugs

Put new plugs in it. My D2 pony did similar things and there was rust on the plugs. A new set of plugs fixed mine.
Chuck C

All - great feedback. The plugs don't have but a few hours on the, but were not replaced after the rebuild. Before the rebuild, #2 cylinder was gouged up pretty badly and leaking oil past the rings, so the plugs don't relate what's going on now. I was going to replace them, but the last time I stopped by Autozone they didn't have any. I'll make it a priority to replace them. Jim - when I added coolant, I forgot to open the bleeder valve on the manifold until after I added the coolant, so there was coolant in the pony, but probably air pockets too. The bleeder valve was opened this time, and I jacked the tractor up on the right side to ensure the valve was the highest part of the pony. Neil - I'm probably several hours at best away from anyone who could look at it, so probably best to try some of these suggestions first. I hope to get to work on it this weekend, but we have a dead combine to get running, so I'll have to work around that. I'll drain the coolant and pull the heads and double check the sequence and confirm that is correct and report back. I really appreciate everyone's contributions to this.

Cat Yellow 1, where are you in VA? I am in Roanoke. I am too much a noob for much help here but would like to meet another member sometime. There are a couple of other members not too far from me. Elton

You only need to pull one head to check the valve timing / rotor as if it is correct on one cylinder it automatically is correct on the other. Both valves will remained closed on the compression and power stroke or for nearly one full revolution of the engine both valves are closed with the firing occurring about halfway during the period both valves are closed. Rotor should point to the wire going to that cylinder when the points begin to open..

yes, this is a great time to replace the sparkplugs, with all the other engine work done etc and trouble-shooting going forward...process of elimination

-plugs are probably the best indicators of what's happening in a gasoline engine cylinder, and some guys that are really experienced can read them like a book...what fuel you are burning, what the temp and mixture is...looking at the ground strap they can tell ignition timing....yada yada yada.....

-obviously they should be very similar if not identical.. or something is horrific is wrong! (okay horrific is a bit exaggerated)(but maybe not)

-this is primarily a diesel form, but gasoline is a different beast