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Are Harley Davidsons That Bad?
The myth is that Harley-Davidson motorcycles are fun, patriotic, valuable, but inefficient and obsolete. They appear to produce much less horsepower than an equivalent J****ese bike, and are therefore technically backward, retrograde and inferior. This is not true. A fair evaluation cannot be made solely on the basis of displacement (1000cc, for example, regardless of motor type). Dr. F. W. Lanchester, one of the earliest true geniuses of the internal combustion engine, analyzed this problem over 90 years ago, and correctly decided that comparing motors on the basis of size only gave an unfair advantage to motors with more cylinders, and favored those with larger bores and shorter strokes. He devised a formula to allow motors with different numbers of cylinders, and different proportions to compete on a fair and equal basis, with the superior product to be determined by the execution of its individual design & construction, regardless of bore and stroke. His original formula needed only slight modification to be accurate today:
HP = B^1.65 × S^.5 × N × C
In plain English, the horsepower of a motor is equal to the Bore taken to the 1.65 power, times the Stroke taken to the .5 power, times the Number of cylinders, times a Constant representing the quality of material available, type of fuel, barometric pressure, temperature, etc. I've arbitrarily chosen to value “C” at 4 for a race motor, and 60% of that, or 2.4 for a street motor, to return a realistic number. For those of you who've forgotten their math, I've used superscript to indicate powers: “B²” is “B squared”, or multiplied by itself; “B^.5” is “square root of B”. Today's pocket calculators make easy work of this. Using this formula, an Evo 80 (81.7cu.in.) motor has its theoretical power calculated as follows:
B = 3.498”, S = 4.25”, N = 2, C = 4 HP = 130 (race), 78 (street)
For comparison, take a “technically superior” Kawasaki motor, the 4-cylinder, double overhead- camshaft, 4-carburetor, big-bore, short-stroke KZ1000 (1015cc, 62 cu. in.):
B = 70mm, S = 66mm, N = 4, C = 4 (same as H-D) HP = 137 (race), 82 (street)
Doesn't look that good now, does it? They should both produce about the same power. But doesn't that make the Kawasaki better? It does the same work, with less displacement? No, it's supposed to!! The Harley-Davidson does not have the advantage of size. The Kawasaki's power is the result of physics, not better quality, as the formula shows!! By the way, side-valve motors, such as the 45, K, and U-Series have also been given another allowance to make up for their restricted breathing and low compression. AMA Class “C” racing permitted 50% more displacement for a side-valve when competing against an OHV or OHC motor. This means that the correction factor for theoretical power for a 45 is not 4, but 2/3 of 4, or 2.67 (2.67 + 50% = 4). The math for a 45:
B = 2.745”, S = 3.8125”, N = 2, C = 2.67; HP = 55 (race), 33 (street)
The KR motor easily beats that - over 60hp in 1969, using regular gas. The K-Model produced 32 hp. So, even Harley-Davidson's oldest types are better than you thought…
Stop apologizing, and be proud of what you ride!

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"Harley-Davidson" name for reference purposes only. Not affiliated with Harley-Davidson Motor Co.
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