Hello everyone, my name is Simon and a recently picked up a 1988 K100rs. It has 81,000 on the odometer and what looks to be a small oil leak from the back of the engine. Might be a clutch boot or rear main seal.
The only experience I have so far is I rebuilt a 1978 Honda cb750 and but I really like the look of the k100 and when the time was right was able to pick one up for a great deal.

I am planning to replace all the rubber, clutch, rear main seal and all the oils and fluids.
With this I will also do the spline lube.

Any advice will be greatly appreciated.

WelKome from another Pacific Northwet member.

I wouldn't replace the rear main seal unless it's leaking. A common source for oil leaks at the rear of the engine is the clutch nut O-ring. Once you take the transmission off to access the clutch you will know what the cause of your oil leak is.

Thank you!
That's exactly what I was going to do. Just assess it when I get into it.