I originally posted this to another forum, but it might be worth repeating here.
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The last of the board-track racers--that were hitting 100-110 MPH--probably had engines that were still only putting out around 10-12 HP.This page has a story on a barn-find 1909 Curtiss:
http://thevintagent.blogspot.com/2009/05/barn-find-1909-curtiss.html
link text--- http://thevintagent.blogspot.com/2009/05/barn-find-1909-curtiss.html
Early on in the text he notes-
"... quite a nice machine in the day with a reliable and powerful inlet-over-exhaust v-twin of 1000cc..."
Beneath the second photo, a couple of figures are given-
" ... The Curtiss weighed all of 160lbs, and was good for around 60mph ..."
Further on it is said-
"... By 1904, a racing motorcycle of 5hp began to make the rounds of competitions, and winning, and he journeyed to Daytona that year to participate in the open speed trials on Ormond/Daytona beach, breaking all the 2- to 10-mile records in the process, averaging 67.41mph for the 10-mile record. ..."
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So from this we can gather a few things:
For a v-twin motorcycle of the 1905-1910 era...
...weight would be ~160 lbs
...top speed would be around 65 mph
Most surprising to me is these two figures-
...v-twin engine would be ~1000cc's
...that engine would only make about 5 hp (!)
By comparison, the 2010 Yamaha YZF-R1 has a 998cc 4-cyl engine that makes about 146 HP.
If you wanted to compare another modern v-twin engine, then the 2011 Harley-Davidson models with a relatively crude 883cc motor makes "only" about 55 HP. Ten times as much.
A modern 5.5 HP lawn tractor engine is a pretty low-performance motor, yet displaces only around 150cc's.
We see a lot of people who wish they could find an engine that would look more authentic than the China bike engines--but the biggest problem you would seem to have would be to keep a modern engine from making too much power....
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