It looks like your brake mount has had some work done to it. The welds are sloppy. It may have been added in or relocated at some point, and the additional mount located behind the axel on your bikes frame does not belong on the bike. I’ve attached a few pics from my bikes that show original locations for the disc brake mount on both sides of the frame (red 400x & black 400TS). The Kelsey Hayes 200m is a difficult set up to find. Someone here might have one they’ll part with or others here have modified aftermarket disc brakes to work. I’ve noticed The original disc brakes never work that well. They’ll slow a bike down, but I just don’t think they have good stopping power. I don’t run the disc brakes on my bikes. Instead, I’ve converted all my bikes to a clutch band brake setup.
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