Broken oil pump drive 75/5

[dunne7684]

Hi
last summer i bought a 1972 75/5 SWB.21k miles. Only two previous owners as far as i know. Being a Lic. mechanic and from listening to the engine noises i decided to have a look at the pistons and bores. Pistons were worn pretty good. Got rebore done and put it on the road and rode it for the fall. It ran pretty well. This winter decided to see what else was worn. Timing was sloppy in the timing hole so i decided to look at timing chain and sprockets. Cut that endless chain off and pulled camshaft to inspect lobes etc. When the camshaft came out the woodruff key was sitting in its slot but the drive side of the slot was broken out. The broken piece was still there as was woodruff key but same was worn on the side. It looked like this had been like it was for some time. Camshaft lobes are perfect. Can anyone see any problem in getting a new woodruff key and having a new slot cut in the shaft 180 deg from old slot. Also where can i get a duplex chain with master link as i hate not being able to take things apart easily.

[schrader7032]

I can't help much with the woodruff key. You might have a idea but don't know if cutting the new slot would weaken the camshaft any.

As for the timing chain, check Ted Porter at http://www.beemershop.com or Hucky at http://www.bmwhucky.com/. They both show the chain with masterlink on their websites. I'm sure there are more such as Bob's BMW, Max BMW, Capital Cycle, Motobins (Europe), etc.

[dunne7684]

Hi
As the woodruff key is only driving the pump rotor and i cannot see it putting enough stress on the shaft to cause a problem , or for that matter causing an imbalance for such a small amount of material ( the piece that broke out). I will be replacing the oil pump as the tips of the rotor are worn and i can get a 0.012 feeler gauge in at the tip..
As for the cause of this in the first place, i seem to remember some auto engines in the mid 80s that sheared the drive to the oil pump if cranked over in really cold conditions. I wonder if this trouble of mine happened under similar conditions or if a small piece of something hard being ingested into the pump caused a momentary high torque situation. For a engine with only 21 K on it any wear i have seen all comes back to not changing the oil at regular intervals in the past history.
Thank you for the web sites i will have a look. With with a couple of more parts and a bit of time i should have this baby on the road for springtime.