I've got a 1982 613 (531 DB main triangle, Ishiwata Magny 10 stays and fork blades). No inner tangs. Interesting data point, I was soaking tubes in Evaporust due to bad top tube rust and a few spots along the frame (all consistent with a heavy sweater). When I was done I also figured I'd soak the fork, since I knew some of the history of these forks and also that there was some rust (superficial or not) around the cracks typically.
1) The fork blades (Ishiwata Magny 10) had a tremendous amount of black material come out after Evaporust soak
2) The frame stays (Ishiwata Magny 10) had a tremendous amount of black material come out after Evaporust soak
My understanding is the black material from Evaporust soaking is dirt/debris and/or the chelated iron (I could be getting this wrong but I believe Evaporust is a chelator Edit: looked this up and it's probably the carbon from the steel and/or ferric sulfate that it converts the ferric oxide to). For once all those years of Chemistry for ChE helps. Is there some possibility the Ishiwata materials were stored/finished/uncoated improperly where they were more prone to rusting? Exterior of all these surfaces, sans the 531 main triangle from sweat I believe, was/is in great condition.
Also I believe my steerer was a Tange also. I briefly used a Tange CrMo aftermarket fork from around the 90s while I played around with configuration and waiting for a shorter stack headset. Ride wasn't quite as good as the stock fork, I feel comfortable declaring.
Last edited by AJI125; 06-14-21 at 08:12 AM.