Just got a 1973 RT3.  Owner's manual says premium gas.  I'm more familiar with 4 stroke bikes. Usually with High compression  bikes premium is required.  This is low compression so why would I need premium gas?  Thanks

I run 93 octane pump gas without ethanol in all my Enduros as well as my tree service equipment (chainsaws, blowers, trimmers). I store it in metal cans.  Everything runs very well.

2 stroke oil lowers the octane a little bit.

This topic is subject to a lot of discussion and opinion.

"I think", might be wrong but!!, Japanese low compression really isn't. It's just that it's quoted from the time the exhaust port closes. So randomly guessing here--7-1 might be 10-1 actual. Someone sort me out lol now i've stirred the pot.

You're not wrong RT325...  measured "normally" they are over 10:1...  possibly as high as 12:1. 

That said, two strokes don't require a lot of octane.  Owner's manual says "90+ octane" and actual warns against using "ethyl" which was premium at the time as it contained high amounts of (tetra-ethyl) lead.  Manual also says "ethyl" was 100+ octane. 

Important to note, just as Japanese had a screwy way of rating compression, gasoline in the USA uses a different rating system today.  Back then octane was the "Research Octane Number".  Today they use an average of the "Research Octane Number" (RON) and the "Motor Octane Number" (MON).

MON is a much more realistic and demanding test for vehicle engines and always results in lower numbers than the RON rating. 

Plain old modern USA "89" regular will have an RON of well over 90 and easily meets the octane requirements in the manual. 

WE’RE NOT WORTHY
WE’RE NOT WORTHY

Thanks MarkT, i knew you'd have the answer. Now i'll stump ya--or not. What octane would the mineral turpentine be that i poured into the open inlet port of my Excelsior 125 in about 1958. Started in a couple of kick & i ran away as it revved it nuts off--then stopped pretty quick & no harm done. Didn't try that again lol. I was walking past the shed or getting my pushbike to go to school & thought--i wonder--bottle on the shed wall--just tip a bit in & see what happens haha. Couple of google pics of exact model. Might be hard to see but i could knee change the gears perfectly. No positive stop but got good at knowing how far to knee it to the detent of second in the 3 speed box. Faster than Dad's Bantam. Loved that bike--espoecialy with the mufflers off lol.