two tired gets good economy because he probably tries to
Not sure what you mean by this. I'm not making any concerted effort for fuel economy beside keeping it in tune. It's a combination of city and highway driving and I flog them when driving, keeping the engine in the power RPM band, except for highway cruise and stopped. 70 and 80MPH is routine on the highway. (It's true that my last few years of driving have been a bit tamer, as with warfarin in the system a let off from the bike will bring a likelihood of bleeding to death. But, my mileage reports are from the era prior to that.)
The mileage reported applies to my 74 550K, 76 Cb550F, and my 77 Cb550F. The 78 CB550K actually gets better mileage than the others, probably due to its factory lean burn tuning.
I had a 75 Cb550K that got about 35-40 MPG, but that had a 16T front sprocket, and didn't see much highway use because of it (and the noisy Mac 4 into 1). Sold that bike a few years ago.
The other bikes have the stock pipes, and air box. All but the 78 CB550K got a UNI NU-4055 air filter installed.
With the stock sprockets and tire sizes on the CB550, the MPH per 1000 RPM is 12.24 in 5th gear. 5000RPM would be 61 MPH
The CB500 is 12.65 MPH per 1000 RPM in top gear. 5000RPM would be 63 MPH.
However, look at the speedometer errors reported when these were new. And remember, tire height changes will also effect indications.
I should add that the 74 Cb550 has a Windjammer fairing on it.
The 76 CB550F has a Quicksilver fairing on it.
The 77 CB550F has a National cycle fairing on it.
The now sold 75 CB550K did not and neither does the 78 CB550K (which I will sell next).
It wouldn't surprise me that the faired bikes get better mileage at least in part because of the fairings. But, I certainly rode them the most because they had fairings. I much prefer a more upright position on the bike rather than laying on the tank. So, perhaps a riding position that creates more wind drag on an unfaired bike has a toll in the mileage department?
Cheers,
