Early Commando Crankcase Upgrade Confusion

Hi all,

I have some damage to my crankcase as well as a lot of connecting rod play so i decided to split the cases, get the crank ground and repair the damage.

Since I have the cases apart, I decided to plug the holes that lead to the timing side, block the stock oil return hole and cut back the oil scraper flange. I just split the cases and noticed there is no return hole to plug and no oil scraper flange to cut back! So how the heck does the oil from the cases return to the pump? If anyone could explain how the oil feeds through my Commando, that would be greatly appreciated. It's a 1971 and I was planning on get Jim's crankcase breather from NYC Norton.

I should also ask, I'm getting superblend bearings. I do plan on checking end float of course, but are the superblends a direct swap out from the older style bearings?

Cheers
Dan

danfr said:

I just split the cases and noticed there is no return hole to plug and no oil scraper flange to cut back! So how the heck does the oil from the cases return to the pump? If anyone could explain how the oil feeds through my Commando, that would be greatly appreciated.

Click to expand...

The oilway drilling is there in your first picture.

So how the heck does the oil from the cases return to the pump?

Well, you see the big sump plug on the drive side case? Right, oil that accumulates in the sump is drawn in there...then you see a hole in the mating face that isn't a bolt hole, and you can see it goes to the sumpl plug...Still with me?

Then you should see the hole in the timing side mating face that lines up with this hole...this hole is the start of the oil passage that goes to the scavenge side of the oil pump!

The small 'bump' right inside that case is where the passageway drilling from the pump end is. Of course it changed angle to go up to the pump.

L.A.B. said:

The oilway drilling is there in your first picture.

Click to expand...

If you’re talking about the hole on the timing side of the case at 4 o clock, I added that one about three or so years ago.

Ah! it looks like the oil is picked up through the drain plug screen.

danfr said:

Ah! it looks like the oil is picked up through the drain plug screen.

Click to expand...

Yes, then goes to the timing side case through the drilling on that side and that connects to a vertical drilling
to the oil pump.

The scavenge modification is intended for 200000+ series 750 crankcases that do not have the sump strainer plug.

Thanks for the replies. Nice to know I don’t need to do the mod to be honest. I don’t have access to a mill.

I tapped the holes with 3/8 UNF in the old oil return hole and 7/16 UNF in the two other holes. I have some stainless set screws but hopefully can track some brass ones.

cheers