in 1974 yamaha imported the tz 700 4cyl road racer producing 90 - 100bhp would hit 170 mph run on 16/1 ratio. running massive main jets, loads of smoke. warm engine up on soft plugs and then when engine temp was up change them for hard types the fuel you mixed then you had to use in 24hrs or it would separate if let standing and could nt be remixed again by shaking!!. as the quality of oil improved so the ratios got thinner, less siezures. more reliable running no messing with plugs etc. so when the high grade oils appeared such as belray oil, in the early eighties i was runnning tz 250/350 yams at 50/1 with more power and reliability with no significant wear problems.thats over 25yrs ago!. i recon they know what ratios to run in saws this day and age with no fear.