[quote name='joepotts7' date='Jun 18 2009, 10:52' post='3700147']
The Works spine frame Jim Lee Yam (seen here) was done for the start of the 1970 season. Only the one was made and it raced for two years. I believe Tony Foale did his spine frame a few years later (1973). The disk brake pictured is not the original (but I have the original, plus the original caliper mount). The original disk came from a Hillman Hunter car (Jim used these plenty). With regards to helping with dimensions, given Jim only built one bike, I think it should stay that way. I would prefer it that no one tried to replicate the frame. I am a big fan of one-off specials, and I am always uncomfortable with the idea of them being replicated (a one-off is just that and it should not be reproduced to be used in classic racing, especially if the original survives!). For example, the number of times my dad has been asked to replicate his 4 valve Velo. Only one 4 valve Velo was built (one frame - Jim Lee again, two heads cast, one special gearbox etc etc) - below is a shot of it:
I obviously can't stop you making a version (I know you are not making a replica) of the JL Yamaha, but I would feel more comfortable if it was not meant to be a Jim Lee frame. I know of a few very famous racing bikes that are said to be the ex xxxx bike built in yyyyy, but actually cannot be the bike - I better not say any more! One advantage for a Foale frame based bike, is that you could contact Tony and at least get blessing for the project. Another option is to get one of Jim's customer Yamaha frames. These were very light frames duplex built eary on (aircooled). I don't mean to be a miserable bugger with regads to the JL spine frame, but I hope you understand my reasons....
A mate from years back (Trevor Hallam) used to race a JL Yam 350 at Darley and other Mids/North circuits.It was quick and so was he,but I remember he spent quite a lot of time perfecting his welding technique!
The JL Velo 4 valve;is that the one that Hulls' Tony Myers rides,or are we talking of 2 different machines? Tony's grandson is a mate of my youngest,and I get to hear about his exploits!