Seems to me and engine that is pinging will show very light color spark plug deposits, and possibly a white center electrode insulator. Combustion temps will be high and should, at least, keep the plugs very clean. Possibly the outer ring won't have the desired blackness, either.
It is common for many people used to autos that cruise at low RPMs in overdrive (making about 10-20HP in cruise), to be uncomfortable using smaller displacement engines in a Higher RPM mode. One symptom is that people "lug" the motors, asking for max power and torque well below an RPM that the camshaft profile works efficiently. Many auto engines rarely operate above 4500 RPM. And, their cams are profiled to supply best power and/or torque below that RPM. Those engines have no hope of operating at 9000 RPM with their current cams and valve train. Conversely the cam in the SOHC4 is optimized to achieve best power in the upper half of the RPM range. The result is relatively poor volumetric efficiency at lower RPMs. Simply twisting the throttle at low RPM is lugging the engine until you get into the upper 2/3rds of the RPM range when the cam begins to operate in an efficient manner for this engine's breathing characteristics. With these engines you aren't being kind to them by keeping their RPMs low. They were designed to be Reved up and operate better, with less strain on them in the upper RPM bands. If the noise that the SOHC4 makes upsets you, perhaps a quieter intake and exhaust setup would be more to your liking. Or, even another choice of motorcycles that are designed to cruise at low RPMs.
Lugging the engine, particularly with lean mixtures or glowing embers in the combustion chamber, can lead to pinging and even detonation. This can lead to some pretty severe premature mechanical wear.
Perhaps if you think about percentage of power it will help assuage the cringing effect the tach needle has on you? The power band starts about 1/3 up from the range of the band. The Cb550, for example, has an 8000 RPM rev range From 1000 to 9200. 1/3 of that is 3700. That's only 30% power. And, come to think of it, 3500 is about the lowest I like to see on the tach while driving about in city traffic. When I want response, 4000 and lower gears for even more Rs is what I like to see. Cruising at 5000 is only 50% power or half capacity for the motor. Heck, that's just loafing!
The cam grinds on these bikes are to make horsepower at higher RPMS. In doing so, they sacrifice torque at lower RPMS. They are designed to be reved up and are happiest when they are doing what they are supposed to do. None of my 550s have complained about this treatment. Could the 750s be more dainty or fragile? Seems unlikely.
As to the clicking noise, who knows what the printed word click means relative to an actual engine noise. When I put the big Vetter on a Cb550 years ago, I investigated the new noises I heard until I took it back off and discovered the engine then sounded just like it did before the addition. Engine noises were bouncing off the fairing right into my face in the quiet air pocket behind the windshield. Still, I knew the plug conditions hadn't changed, the valves were set right, and the ign timing was spot on. There's a lot of metal moving about at 4000 RPM. Noises are going to happen.
Cheers,
