Motorcycle specifications get interesting when comparing the construction of the highest performing sport motorcycles. Subtle differences in rake, trail, and wheelbase combined with an array of race results, illustrate the holy grail of power and handling has yet to be found. Motorcyclist magazine recently ran two monthly issues back-to-back comparing 8 of the top liter bikes in the world. On paper, the differences are very slim.
Consider these numbers:
|Wheelbase: 55.25 inches
|Wheelbase: 55.7 inches
|Rake: 24.5 degrees
|Rake: 24 degrees
|Torque: 100 – 125+ lbs.-ft
|Torque: 75.1 lbs.-ft
Specs and bench racing only go so far and aren’t nearly as fun as seat time, however, the significant difference in torque listed above is worth discussing. The torque in bold letters is from Harley-Davidson’s Twin Cam motor, not one of the 8 liter bikes in Motorcyclist’s test, but why are we including them in a discussion of sport motorcycles that have a 55-56 inch wheelbase and how does HD fit into either of those topics?
The specs on the left are from a bike built by Curt Winter of BTR Moto. Curt accomplished this sport bike geometry by creating his own transmission for the Twin Cam motor. You read that correctly, this is not a Sportster or Buell motor, someone used their imagination and skill to build a drive train and chassis that will put the big block Harley torque to good use on a tight road or track.
A stock, big block HD motor, backed up by a warranty, now produces over 100+ ft lbs. of torque. Common hot-rodding techniques and larger twin cam engines from S&S or Jim’s can take the HD engines well into the triple-digit torque range, hence the numbers listed above. The torque, hot-rod options, tuned sound and serviceability of these motors are no longer confined to feet forward, heavy cruisers. Notice the tiny differences in the geometry specs? Those on the right are from a 2012 Yamaha R1. Curt shoe-horned the big block motor into his very own sport bike chassis with measurements you would expect for an inline four.
He built the frame, swing arm, gas tank, and machined (by hand) various structural pieces. The tank features a cool-looking yet even better functioning vertical velocity stack for the Weber carburetor. He modified and painted an after market fairing and tail section for this track day version. This engine and transmission package will make cool Sport Touring and Cafe Racers as well.
The torque debate may continue forever but it can be argued that lots of low-end torque in a strong and sporty chassis like this results in great seat time and performance you would never expect from a big twin Harley.
Great Job Curt.
Link: BTR Moto
Thanks, Doug, for this news of Curt’s new bike! It will be interesting to see how it performs with a sporty chassis that can make the most of all of that torque. Be sure to check out Doug’s really cool Made in the USA products at Race Track Style.