The oil pump looks pretty good inside. It's almost looks new.. I'm thinking to cut off the primary oiler and drill / tap the hole for a small screw then add it to the cover. I can cut a flat for the screw.
Also there seems to be a narrow groove for the oil return. It seems like it could be widened a little..

 

Rather than destroying a very limited production part, why not just upgrade to an aluminum pump and sell the original?

 

Do you want to buy this pump?

 

BTW. Here is an older one with the return passage machined right..

 

Completely cleaned the oil pump and guess what? The slot is the same.. It was a piece of gasket covering the slot.

 

I cleaned up the cam case gasket surface. Only took off about 5-6 thou.. You can kind of see where the high and low spots were, right next to each other. the rest of the case was in the middle. You can still see some of dings in the surface.

 

I got new timmer and idler gear shafts as the older ones were worn over 0.0015, Bushings were loose also.. Had about 0.0045 clearance. Instead if buying aftermarket HD style bushings I bought standard sleeve bearings and cut to fit. The Od of the sleeve bearing were claimed to be 11/16 -0.000 + 0.001. They ended up being + 0.0025. I measured the bores on the gears, and the idler was spot on but the timing gear was a little large in the distributor gear side and small on the gear side. I tried to set the inner boar on the bushing a little bit large so when pressed in the were close.. Idler gear cam out spot on but gear side of the timer gear was a little tight. I ended up with a using my makeshift alignment reamer to get it to size. BTW the shafts looked good but were about 0.0005 smaller than the originals. I'll probably use a little bearing lock in the case when installing them.

 

Timing plug was stripped. The guy used a 5/8 oversized drain plug to plug the hole in the process, cracked the case slightly. I bored out the plug to 0.625 and taped to 11/16-16.
Had ro remove about 0.025 for the crack to go away.

 

The plug was made out of 303 SS.

 

We never fix a plug that way and your skill lets you do things like that - we weld it solid and drill it dead center so the crack does not come back, yours could - that sucks in the first or second time you remove it once its all together its even thinner and — and it cracked

the oil pump is worth around 300 bucks - drilling and tapping 10/24 because its crumbling type cast iron is what we have done before - but the last 20 years I solder the pipe center closed then we re install it with the hose as well as the vent hose to the frame center to mimic the original look as it matters on that type of machine

cutting the cases when a Yama 4 will seal them — you need to look at the location of the drip hole on the race exit and make sure its going into the roller cage and not being blocked by the cage its self - or you will lean out the feed for the pinion as its only hap Hasard drip oil - your jug spicket diameter shoud be ok but I have seen them tight oem and the gasket drain holes should be ok as well the jug small hole is not used 65 engines, but use a cosmetic cam cover gasket as its thicker then the paper and the oil jet Screw does not like being blocked as you removed material from both the cam cover and the block

using the worn flywheel washers might help with it in the side clearance

its a 35 thousand dollar machine in todays market but no knowing what you did to it would give you anything for it as its a maybe it will work