« Reply #3 on: July 22, 2012, 09:12:19 pm »
I guess my Trackmaster motocross frame to suit the Yamaha YZ125 X/C might fit the bill. It takes the dodgy period monoshock out of the equation, replacing it with a good honest twin shock set up.
If anyone did make an aftermarket frame for the mid seventies YZ's it'll be sure to be an American, I vaguely recall seeing a Pro-Fab or C&J (or perhaps both) monoshock frame.
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'68 Yamaha DT1 enduro, '69 Yamaha 'DT1 from Hell' '69 DT1'Dunger from Hell, '69 Cheney Yamaha 360, 70 Maico 350 (2 off), '68 Hindall Ducati 250, Hindall RT2MX, Hindall YZ250a , Cycle Factory RT2MX flat tracker, Yamaha 1T250J, Maico 250 trials, '71, Boyd and Stellings TM400, Shell OW72,750 Yamaha