1941 Cat 212 1R D3400 Grader, Hunts at idle.

The hunting is just worn governor components........ A fact of life with old machines. If you don’t want it to do that usually raising the low idle setting 50 or 100 rpm will damp it out. It’s an easy test, just open the throttle slightly and see if the hunting stops.

I expect the hard starting when cold is normal or rather to be expected with old worn engines. It’s certainly what I see with EVERY diesel I own. The fuel injection adjustments are a great idea, but can not compensate for wear in the cylinders, pistons and rings.

The pony exhaust leaking into the diesel intake should not interfere with starting the main because the main turning over is drawing in plenty of fresh air.

Blowing out oil from the air cleaner is not normal. Only time I’ve ever seen that is when pull starting with transmission in wrong gear combination and engine was actually turning backwards. I wonder if you have a restriction in the exhaust manifold or muffler (does it have one?). That way you would get some back pressure and possibly make the flow reverse through the metal wool packing. Could some of the removable screens in the air cleaner be missing? I’ve seen some badly restricted manifolds that you could hardly get a finger through the restriction formed by carbon accumulation.

The leaking pony exhaust heat exchanger tube through the diesel intake is a potential engine killer as it is a place for dust to be sucked into the diesel during operation. It doesn’t take much of a leak to “dust” an engine. On modern engines it’s typically something as simple as a loose clamp holding a piece of hose on an intake pipe. We place a lot of confidence in a $2 clamp to protect an engine worth manu thousands of $. You should be able to block off intake and exhaust stacks on the diesel and run the pony to confirm or refute the possibility of a leaking heat exchanger tube.

Hi Team,
this condition likely due to leaking--sticky, bent, inlet valve.
I have also encountered an engine that had an exhaust valve with excessive lash clearance or not opening at all, this is usually coupled with a banging noise in the inlet manifold as trapped cylinder pressure, not exhausted via the exhaust valve, blows back into the inlet manifold when the inlet valve opens.
Similar symptoms can also be from an exhaust valve with a bent push rod not opening fully.
Cheers,
Eddie B.