Most of the simple "no loss" upgrade is in brakes, and a little in weight of parts. You'll find damping "upgrades" to be very tricky with modern forks as they're often not even closely valved or sprung to what you want and start to cost a lot to change. As for the whole front ends, the problem is that you end up with all kinds of geometry problems unless you're more interested in the current "Coffee Racer" trend instead of actual performance.
Tips:
- Most things from the mid to low 80's are running higher offset triples and similar fork lengths (due to similar rake angles on the double cradle frames)
- Most modern front ends run ~0.5"-1.5" offset triples with very steep frame rake. Also makes the forks shorter (which drops the bike), will generally not be compatible without a lot of work.
- If you can get a set of opposed piston calipers, I find that the feel and the maintenance make them worthwhile.
- 37mm tubes are plenty stiff for SOHC4 weight, and a set of gold valve emulators or something similar plus a well set up front end (progressive springs, good oil, good seals) will get you to something reasonably well handling.
- Pick a front end, pick brakes, then size up master cylinder, and if you want compatibility, run the same model clutch control and adapt the cables. Ends are easy to change.
- If you can find something that takes an alloy stem and alloy lower clamp, you'll save a nice bit of weight, and be in good shape.
The ideal, simple, bolt on solution is to just go with a set of 900F (or other conventional forks with similar rotor spacing, offset, and length to stock) forks and use the 2 pot brakes up front or adapt something like fishhead brakes does. Then pick a decent modern master and clutch setup to go with it.
