Tire mounting lubricant
Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
In the past I've used all manner of lubricants from soap to WD-40. I never had any trouble with any of them, though I was always careful to wash off the excess.
Several years ago I bought a gallon of the real stuff and I've been using it ever since. It is inexpensive, lasts a long time, and does a great job.