Honda set the world's standard of motorcycle reliability with the CB750 and the other SOHC4 engines. The brakes were too big in the beginning, and chains were not strong enough
Over the years the brake pad makers (disc) have lessened the gripping power of the pads, selling them cheaper, which pretty well drove Honda out of that spares market (they now buy them from 3rd party vendors).
Diamond and Reynolds stepped up in the chain market to fix this weakness, and the whole world benefitted from their moves to improve chains as the result.
The first motorcycle to ever go 100,000 miles without a rebuild was the gawd-awful looking BMW 600 opposed twin, but its 0-60 MPH time was measured with an hourglass. The next one was the CB750K0, with 1/4 mile times in the 12s.
Since these SOHC4 bikes, the only other bikes to make the no-repair distinction for the 100,000 mile mark were bikes that followed the Honda design, either SOHC4 style (Kaw, Suzy) or Gold Wing style.
It wasn't until the late 1990s that Harleys ever made that trip, and I have only heard it by innuendo, not an odomoeter check.
The weakest link on SOHC4 bikes is their battery (it must be removed when not in use for 4 months or more, especially in winter), because it is small. The next spot is the points, which can be resolved in many ways, like with my Transistorized Ignition. After those 2 items, the rest of their reliability is up to the owner, who must lube the chain when needed and change the oil and tires. That's all it takes to reach 100,000 miles.
So, is that unreliable? And, compared to what?