Here a pic of my one year younger ProRacer. It is basicly the same frame as your RoadRacer, but there are a couple things different: pearl orange, brazed on cable guides and painted tail.
With the full Champion #2 tubing the frame is comparable with a 531 butted frame, but finishing and in particular paint are nicer than with the average competitor's frame that was available at the time. The lug cut outs are enamelled, the BB shell is open, the vertical drop outs are chromed etc etc ...and of course Japanese typical flawless in execution. All things your frame has too.
Large pic under this link
This ProRacer is equipped with Dura-Ace EX. Nice post by Sugino and stem comes from SR (Super Light with flutes). Under the shown black tape sits brown cotton. The pic is of the previous owner. The bike didn't see much use with him, what is good for me.
When the FullPro and FullPro-L were introduced in 1980, the ProRacer disappeared. I think it sat too close to the FullPro of that year. A year later the FullPro went a tiny little bit upward and room was created for a ProRacer with slightly heavier tubing for fork and tail and the cut outs were no longer enamelled. Bottom line is the late 70s ProRacers had really fine chassis and it is unique your RoadRacer shares its frame with it.
that is one STUNNING Koga!! That colour is sooo nice... Thanks for the info on Koga/my ride!
In june I'm going up the Mont Ventoux, and of course I'd love to go on my Koga. One thing that has to be changed though, and that's the gearing...
I did the Alp and the Galibier with 39 - 25 without any problems, but I'm 4 kg heavier now and don't know how trained I'll be by then. (Starting my own practice takes a lot of time...)
I'm thinking about buying an eighties MTB crankset (110 BCD) and make it into a temporary retro compact. Any ideas? Shimano will be better too, cause of the 130 BCD.
What sizes of freewheels can I get? I did come across some Dura Ace with a 14-25 tooth range.