Well, most of the tires used on the CB750's seem to come out to about 26" diameter, whether they're a 21" rim with a skinny tire or a 16" rim with a fat donut. So, the question becomes, how level do you want the bottom frame rails to sit? If you want them perfectly flat, then assume the rear axle centerline is 13" off the ground and stick some blocks or whatever under the rear axle to elevate the chassis to that height. Then rotate the front of the chassis around the rear axle axis until the lower frame rails are where you want them to be, and stick some more blocks under the front and/or sides of the chassis to set it's height.

Then stick a broom stick or, better still, a wood dowel like you use as a closet rod, through the steering tube until it hits the ground in front of the bike. Now measure with a metal ruler (I like a locked tape measure that will stand on it's own) to 13" perpendicular to the ground and note the intersection of the end of the ruler and the wood dowel. The distance from that point to the bottom of the steering head is the length you'll want for your front end. These numbers will change if you decide to run a 10" inch wheel or something equally unusual at either end of the bike. I assume the amount of your front suspension sag will depend on the type and condition of your parts, so you'll need to compensate slightly for that.

I'm a newbie to all this, so there may be a better/easier/faster way to do it, but this one is mine. Any direction from our more experienced builders would, I'm sure, be appreciated by all, especially me! image RR

If you're not living on the edge, you're taking up too much room!
Last Edited By: Ricky Racer 01/27/08 10:26 PM. Edited 1 times.