BMWMCCWA

Just acquired a 1975 R90S but have some conflicting advice on recommended fuel (standard unleaded vs higher octane premium) and lead replacement additives. Best advice?

some of the riders with early bikes use a lead additive because of valve wear. I would get professional advice from one of the BMW mechanics that work on bmws that are around town.Very easy to burn out valves with the wrong fuel.

Yes, I agree with Goldie. I have a R90S, which is a higher compression ratio motor than the others and hence it does not like running on the low octane petrol. I always use 98 octane and even with that, it still pinks at 2000 rpm, or less, if I open the throttle too heavily. My old, 5:1 CR R50 would probably run on candle wax, it is so versatile but I still use the 98 octane (the motor runs cooler as a result) Just to be safe, I always add 1ml of lead replacement to every litre of fuel on the old beemers.
John