Sounds like a nice find!
The early K0 models had an issue with cam chains because Honda had not yet discovered a sonvenient way to oil the chain at proloned racing RPM, and the comment showed up in the post-mortem of the famous 1970 Daytona race with Bugsy riding it to the win. From that day forward, it was assumed that Honda never "fixed" this issue, which simply wasn't true. What is true: it's the same size chain as used in the CB350/305/250.
The slippers and roller on these cam chain systems normally wear out at around 50k-75k miles: they get grooves cut in them, right down to the metal, which then shows up in the oil filter as tiny silver filings. Cut apart the filter element to find it. It's so fine that I have seen it pass through a Honda filter element! When it does, it embeds itself in the main/rod bearings, which is OK: this is supposed to happen in plain-bearing engines, to protect the journals (as opposed to roller-bearing bottom ends, which then grind themselves up...).
I remember some people doing some nasty "adjustments" to these cam chains, because the magazines kept dwelling on how it was the "weak link" in the CB750 engine (maybe because there was not anything else bad to say about this bike ? ). One racing magazine purported to get "better operation" by loosening the adjuster bolt and "pressing in, hard, on the piston while retightening the bolt". This could cause excessive chain pressures on the tensioners, wearing them out. And, sure enough, I saw some bikes where this had been done, and the owner would admit doing it if you asked him. Often, though, these were the same guys who bought those clear red sparkplug wires and spliced them into the stock wires "because they make more horsepower", etc.
Generally, some riders were annoyed by the topend noises the CB750 made, especially if they rode behind a fairing, after the Gold Wing showed up. This was more because the 'Wing was so silent, not because the 750 was so noisy. Cycle magazine, in particular, was notorious for this comment: they had one particularly picky (I prefer "snobby") rider who seemed to feel that touring bikes should sound like his Cadillac. When this guy was writing for Cycle, I heard lots of "knowing" riders commenting on the "noisy camchain" in their 750s. Strangely enough, this noise is due to wear in the two middle cam support bearings, not the chain system itself, and changing the chain makes no difference in the noise in the end. This wear came from too-long oil change intervals on the owner's part, and usually they were using 10w40 oils.
Mine is noisy now, despite changing the chain and all tensioner parts last year. so when I tear into it next time, I hope to create a method of restoring the cam bearings to the stock .003" clearances. My clearances are .012" in the center 2 bearings (
).
