I use a small 12V motorcycle battery to power my timing light and trigger the flash with either the #1 or #6 spark plug wire, whichever one is convenient to reach. Just run a ground wire from the negative post of the battery to the vehicle frame or engine.

Running a 10 weight oil in a stovebolt engine probably isn't a good idea. No matter what the "high" viscosity number is, the oil is going to be too thin to give the parts a good cushioning film of lubricant to ride on. I use 15W-40 in everything we own, including lawn mowers, cars, trucks, motorcycles, generators, etc. No problems yet!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!