They are around, more than one person made them on here, i got a cool idea for a new easier to install, lighter one..
"Easier to install" in what way? One with no welding would be super cool. There has to be a way some type of a sleeve with a snug fit and drill a hole at each end for some bolts to go through the sleeve and the frame tube to lock them together. Hell some people run them without putting any thing back on with a stock motor. I think if you could come up with a no weld solution it would sell big time. I'll volunteer to be the test dummy test subject. If anyone can do it it would be you 754
Both Carpy and CycleX sell such versions of the frame tube kit. My version is a ca. 1980 APE kit which was a tubes and sleeves affair. No welding.
Thanks MCRider for the heads up I sure did not know about those I have only seen the ones where you have to weld.
The one developed by a forum member, aka the Gordon Kit, though it's not Gordon who developed them, is the weld in style. IT is certainly well thought out and beefy. Robust as the engineers would say. Probably $300+ incl the labor.
At the other end of the scale is the APE Kit. I bought mine in 1980 or so, when people were hacking out frame tubes by the thousands and many didn't even try to replace them...with anything. IT was simply 2 replacement frame tubes, and 4 sleeves, and 8 hardened bolts, for $29.95. 2013 inflation price prob ably around $100. I installed mine, with a hacksaw and a drill, roadraced, then toured, often overloaded, 2 up for at least 50,000 miles and at least by the seat of pants, no issues. But, Big Jay at APE said he would not bring them back.
In between lie the Carpy Kit and the CycleX kit. I have no experience with them, but I wouldn't hesitate using either, based oon my experience. I see CycleX kit requires welding and doesn't have any cross tube bracing (neither did the APE kit) Carpy's Kit is then more like the APE kit, in that it supplies replacement tubes and sleeves, with the plus of a cross brace, and the negative that you have to drill your own holes. Be careful where you drill or your bolt may foul on a carb/airfilter part.
http://www.cb750cafe.com/products-page/frame-adapter-kit/