I have tried several different centre stands on 81-83 R100 bikes. It seems that only the ones from those years fit properly, without any major modifications. That being said, the stops on the stock stand do wear to the point where it will end up being way to far forward. There are numerous threads and pages on the web that go into detail as to how to fix the stops. It involves welding and filling to build up the lost battered material and then grinding down enough to make it work properly again. Also, check the holes in your stand to ensure they have not gone egg shaped. And check the bushings, they are prone to wear and cracking.
Many people have changed to the Reynolds stand, and when they want to take off a wheel, they put one or two 2x6s under the stand to get the wheels off the ground. Bit of a pain if you are away from home and need to patch a tube, but it can be done.