I am curious to see what advice you get on this. Those parts look kinda “beat up”. I would have expected smooth and shiny wear. My (same) pump has 155,000, and I don’t have any reason to suspect it’s in trouble, so they must run a long time. Mine got resealed with a new o-ring? at about 105k. 

As an option, I have bought nice used parts from Re-Psycle BMW Parts (re-psycle.com) near Columbus, OH.  Once had to replace my points cam/advance unit. That thing is silly expensive new. Re-Psycle sold me a nice clean used one at a much more reasonable price. It’s still working fine, many years later. 

Welcome Aboard !

You're correct, those parts don't look magnificent, but we don't rebuild engines based on looks alone. There should be a whole set of dimensions and clearances pertaining to the oil pump, or at the very minimum, a range of oil pressures. Those dimensions may not appear in your Haynes manual, but they do exist. Find those dimensions and clearances and then measure them. 

An Airhead with 70,000 miles is barely run in. So it's not clear to me what problems you experienced that required the engine to be dismantled. The oil pump cover's o-ring is the only part of the pump I've ever heard of needing any service. 

Hope this helps.

If you google “bmw airhead oil pump clearance”, you will begin to find some dimensions to check. 

Out of curiosity, I looked at a number of pumps (inner and outer rotors) being sold on eBay. Heck, they all pretty much look like yours (and mine, most likely). May be very normal. 

I also see that euromotoelectrics.com has new parts if replacement is really necessary (set for about $145), but I’m thinking you are probably fine with a new o-ring. Check the dimensions and clearances and see. 

Just wondering if you have made a determination on your oil pump.  Let us know what happens. 

Thanks David and Richard for the advice. With the run up to the holidays I haven't had a chance to work on the bike so haven't made any progress. I'm planning to (1) take Richards advice and check the tollorences and (2) take David's advice and stick it back in and hope for the best provided they are within tolerance.

Will report back once the job is done 🙂

Just one more quick question - I have a '79 R80/7 so was expecting to need a woodruff key, but this is the pump setup i have. Nowhere for a woodruff key to go. Any thoughts?

And the other picture

Well, that is interesting. Apparently, the round shaft with a woodruff key was used for “some /5 models”, according to one parts source. Wonder how that got in your R80/7??  Maybe someone replaced the camshaft with a keyed version at some point??

Anybody else with better knowledge?

So it would then appear that, OTHER THAN “some /5 models”, there is no woodruff key and the inner rotor is locked to the camshaft using the two “flats”. 

Your first photo shows a double flatted hole in the oil pump inner rotor. The second photo shows a double flatted shaft coming out of the engine. Those 2 mating surfaces would negate the need for a key. The center rotor derives all the power it needs more reliably from the double-flatted design. A key may have been used only on earlier models.

When you have doubts or parts questions, the place to look is an official BMW parts manual. These are free, on-line at places like Max and Bob's. With these resources it's easy to compare different year designs and come to know what's supposed to be fitted. When doing extensive repair work it's often necessary to have both types of manuals in front of you. 

Parts manual:  https://shop.maxbmw.com/fiche/PartsFiche.aspx

Hope this helps.

the discussion on this you started on ADV went quite well.