Trying to find out which tape BMW uses for binding their wiring looms (1985 K100RS and 1997 K1200RS).  Wurth have a 19mm adhesive cloth tape designed for that purpose.  So too does TESA.  Anyone have experience doing restorations to original specs?  If so, I'm trying to go BMW original and not plastic electrical tape...

Definitely don't use common electrical tape for your harness. It won't last and its not heat resistant.
You can buy automotive harness tape fairly easily from ebay or go for something with a little reputation. It's pretty cheap anyway.
http://www.carbuilders.com.au/fleece-tape

This stuff:

https://www.banggood.com/Wiring-Loom-Harness-Adhesive-Cloth-Fabric-Tape-Cable-Looms-19mm25m-p-943926.html?rmmds=search&cur_warehouse=CN

Tape - beeugh!!!!!! Use PVC sleeving right the way through, unless you really want the 'original look'. PVC sleeving takes a bit more planning ahead when making the loom but has far better survivability over the long term. As the original loom is a mixture of both, my guess is that tape just made the final assembly quicker on the production line. I haven't used tape when making a new loom in over thirty years because I dislike it that much!