I needed to replace the 100K mile forks on my K3 750. I had a set of longer (#393) forklegs that are in like new condition. I bought a set of fork tubes from VintageCB750.com on the advice from BenelliSEI, thanks John. These appear to be very good quality. Also bought some cheap emulators, then picked up some Racetech .85kg fork springs.
The only issue with the aftermarket stauntions is the ID of the rebound check valve is a full 0.040" larger than the OD of Honda's damper rods. Checking through many original Honda tubes I found three different check valve designs, but all were just slightly larger ID (0.004") than the dampers, which makes sense. (Perhaps with thick fork oil and both original rebound holes welded shut on the damper rods, rebound could be slowed but, in my mind, not adequately.)
So I machined the rolled bottom of the fork tube that holds the check valve in place on both old and new tubes to install OEM check valves in the new tubes.
The check valve I decided on uses a spring washer behind the valve. I just thought it to be the best OEM option. Middle pic. Left is OEM rebound check valve, right is the aftermarket.
Then once installed I just welded the spacer to the bottom of the tube. The tube bottom is tapered here anyway. I had some new damper rod seals, and another nice thing about the replacement fork tubes is they are smooth internally unlike the oem tubes. The damper rod seal is more effective.
I like 15W fork oil, and after a couple rides have drilled three more bleed holes (four total) in the emulator valve plate, and set the emulator preload @ 2.75 turns. The extra bleed holes help absorb sharp bumps in the road surface better. I have settled on a 60mm spacer for main spring preload.
The old is like new again, my old back loves it!
