do you think a tapered rubber bung 9mm diam and 11,5mm diam x 20mm ht would be about right?
For cleaning up the calipers, do I use break fluid and an old toothbrush?
If the bung fits tightly whilst still leaving enough material on top for you to grab when you need to remove it, it will be golden.
I've attached a photo of the "bung" in the final driveon the wife's R65/80, ignore the oil weep marks, I am going to rebuild it this week, for some reason I've had to do 3 final drive rebuilds this year, which is more than I've had to do in the previous 40 years of Airhead onwership. The only thing I'll say is that I am now a dab hand at getting the little bastard of a bearing out that carries the "nose" of the pinion shaft, I've borrowed from the old mechanic's cookbook for removing the clutch bearign or bush from the centre of a flywheel - turn up a piece of steel that just fits inside the bush/bearing and then pack as much grease as possible into the bush/bearing. Insert turned steel drift and then smack the end of it smartly with a big hammer, the grease, having nowhere to go, forces the bush/bearing out.
As to cleaning the caliper - whatever floats your boat, just be sure that when to put it back together that you only use clean brake fluid as assembley lube.