Never owned one but got to ride a friend's 500 Mach III in '69 when they first came out. The power didn't scare me as much as the extreme nosedive and wiggle (near head shake) when I first jumped (and I mean JUMPED) on the front brake. I took off drag race, MX start style and got up to around 95 mph in no time and then got on the brakes hard and the front end took a hard nosedive (thought it may have even bottomed the forks?) and then the wildazz wiggle and front end flex. Forks were too soft and flexed like nothing I'd ridden before. Handling was terrible as I got onto that 500 Mach III from a great handling '69 Triumph T100R 500 Daytona that, BTW, I still own and have to this day (stock Triumph forks and Koni rear shocks). I don't think my T100R Daytona 500 could match the power of that Mach III even at triple (pun) the displacement but that Mach III even with work would never match the handling of the Triumph(s). So to get this thread back OT you could take all of the Triumph twins of that era and make a winning DIRT BIKE during the '60's but never a Mach III