Is there an aftermarket frame for the CX500? Has anyone made one for racing or custom builds? The stock frame is very heavy and uses mild steel. A modern tubular fame would be a great platform for the CX500 drivetrain.
I'm guessing the lack of reply would indicate that's a big NO.
One thing I had thought of though was replacement alloy side plates for the single spine type frame (i.e. most 500s). Not a huge weight saving I know, but there must be quite a few frames where the lower pressed and fabricated rear engine mount sections have rusted badly although the rest is still ok once the rear subframe has been cut off for customisation. So...
What if you cut those lower cross tubes (probably still sound) and remove those fabricated sections, then make some steel plugs with a suitable thread tapped up the centre and press into the ends of the cross tubes and welded in place. You now have 4 good fixing points for some aluminium Swing-Arm pivot side plates to be bolted onto the sides. These could be manufactured differently to suit different Swing/Arm pivot requirements and also for differing footrest mountings and similarly for subframe mounts. Nicely milled alloy would look pretty good and they'd be easily swapped at a later time if you required a slightly different configuration.
Seems doable to me and should enable many currently too rusty frames to be re-used in custom projects since as I said, most of the rust problems seem to be those bottom fabricated sections that would be cut off.
I question the sanity of anyone that does this, but I'm also curious how it would work out. CX500 frames are fairly simple especially if you're doing a cafe-style build. I'm curious what the result would be if someone handy with a TIG was to make one out of aluminum. The only thing that really matters is the proper castor on the front fork and the location of the swingarm pivot in relation to the motor mount pickups but at that point it's not really a CX500, you've built a bike from scratch that happens to have a twisted twin engine.
The frame doesn't weigh as much as you would expect, either - the bare single spine frame is about 20kg stock iirc. If you're chasing tenths on a track with a giant budget then the effort of a custom frame may pay dividends (as if that's the case for anybody) but I don't think that there's a market for that sort of thing.
I really doubt there's a market for a lightweight frame for the CX. If you're that concerned about weight, don't start with the CX engine. But I'd never criticise anyone from doing it anyway. Such projects are fun.
Regarding weight, whatever the calculations appear to show, there is absolutely no question that the older steel frames such as on the CX and e.g. the Gold Wing are monstrously heavy compared to an aluminium frame such as on a VFR or even a BlackBird. I can easily pick up and carry one of those Al frames with one hand, but a CX frame is much very harder to do that with. The Gold Wing frame is even harder, much harder to lift. I have all the above frames here and can testify that there is a huge difference.
This is just reminding me that I have a Vulcan 500 engine with a dropped valve I could probably fix up, as well as a Rebel 250 with engine issues that could use a hilariously overpowered engine. Hmmm...
Lots of interesting comments to my original post. My thought was that there are lots of custom bicycle frame builders out there that are wizards with chrome molly tubing and a tig welding skills.
If you have a frame jig that allows you to determine the critical reference points and some creative skills you could make a custom CX 500 that is really different. Spondon used to make custom frames for Triumphs and Nortons, just wondered if someone might have had too much time and money and made one for the CX500.