Hello, 
I put my faith in a machinist that came highly recommended from a trusted shop, but it has been 5 months of radio silence. I sent out my pony motor's crank shaft to be welded up and ground back to spec. I'm still considering driving a few states over to see what the deal is, but I figured I should start by doing the sensible thing and seeing what it would take to get a new one. Does anyone have an in-spec (standard or available undersize) crank shaft for a D4 starting motor, PN 4B903. 

Additionally since I'm already looking at getting custom pistons to fit this worn out block, does anyone have a good running full-up pony motor they'd be willing to sell? I was rather thrilled with keeping the motor I have as it's original to the this early dozer (D4-7U SN 931), but the reality is that I need it back up and running for some work this summer. 

Thanks!

I have 2 pistons 8h2763 .040 for-D4

I have a crankshaft 5F8405, unsure if that is the same or not if you want to try to research it. Was told it was D4 when I got it but other parts from the same lot were D6. Located in eastern Washington. Good luck, Mike

The 5f8405 crankshaft is for D6

I have a couple of pony motor crankshaft, one is definitely going to need some work. The other one looks ok to the eye and might just need to be polished but I can measure it if you're interested

Aftermarket pistons are made by JP Pistons in Australia, a bit dear around AUD $150-200 per piston, but the USD/AUD exchange rate helps.

TractorDon has a pair of nice running pony motors for sale, he is located north of Salinas, CA. Give him a call, easier than trying to rebuild one IMO. JM