I have a 120/70 on the front of my '98 748 and like it. The 70 has a little more "meat" to protect the rim from pot holes and other hazards. I don't think the bike is any slower with this size than the 60. If all you do is race it on the track I would say stick to the thin wall 60 but if you do 90% of your scoot'n on the DOT roads I would go with the 70. Ever price a new rim for your 748??
Bring lawyers, guns and money to get me out of this.
Thanks for your input. I do ride it on the street, but I place a higher priority on the time it spends on the track.
I have priced rims, and as soon as I regained consciousness the rims that I have seemed perfectly adequate.