We chose the 1200 Sportster for two main reasons. One, it is a lower priced bike. We wanted this to be an affordable project for customers who want to do the same to their bike. We felt that the 1200 Sportster is set at an attainable price to everyday customers. Two, most people do not automatically think of motor performance when they think of a Sportster. The Sportster is typically not thought of a fast bike. Therefore, we wanted to take a small bike and give it a big bike feel.
After deciding what type of bike to use, our first task was to find the right Screamin' Eagle cam to deliver the best lift and duration to allow the most air and fuel we could get into the cylinder. After careful consideration of what we wanted the bike to do, we chose the Pro Sportster High Output cam. With a lift of .575 and a neck breaking 3500 - 7000 RPM range we were certain this would be the perfect cam to feed the beast.
Next, we needed the right set of heads with oversized valves to enable the air and fuel to enter the combustion chamber. The Screamin' Eagle CNC ported heads would surely do the trick. We also wanted to bump up the compression so we went with Screamin' Eagle high compression pistons that when combined with our choice of heads produce an ear piercing 11.3:1 ratio. With this compression ratio 93 octane pump gas would not be an option as pre-detonation would most likely occur under heavy acceleration, to combat this we chose to run 112 octane race gas.
Now that we had the heart and soul of our build figured out, we had to come up with the best non-restrictive air cleaner to allow all the air into the engine we were anticipating. The Screamin' Eagle heavy breather with the industry leading K and N filter element was the perfect addition to our combination. As proven on the dyno most air cleaning elements rob the engine of 3-5 horsepower, the Screamin Eagle heavy breather is the exception to this rule.
Finally, it has been proven the engine can't get it in if it can't get it out, so we had to do some exhaust research. We knew we wanted a equalized 2-1 style system, but there are many options available on the market. After careful consideration we decided to construct our own system using all the tuning knowledge we have gained throughout the years. After some long hours on the dyno and a few burnt fingers we were able to construct a equalized 2-1 system with a collector that coupled with our combination produced a blistering 91 horsepower. The problem that occurred with this exhaust is that we had no way to produce the right sized baffle for low speed riding backpressure. Harley-Davidson® engines want back pressure on the low end of the RPM range and a free flowing pipe for the high end. Due to the fact that we couldn't offer the best of both worlds, the right decision was to search the market for our exhaust. We had a chance to talk with the exhaust building legend Darryl Bassani face to face. After talking with him and getting his understanding of what we were trying to accomplish he was able to recommend his high performance 2-1 equalized exhaust. This exhaust system was a good addition to the bike as we had good response through the low end of the RPMs and was still able to make good top end power.
Our final run came to 88 horsepower, so we did loose some power but gained great rideability. In closing, we did meet our goal of 90 horse power if we were on a drag strip, but with bike having to be driven on the road we settled with a nicely tuned 88 horse power. A special thanks goes out to Darryl Bassani for his time, knowledge and experience.
Lastly, we chose a Screamin' Eagle theme for the aesthetics of the bike. We wanted to have the Screamin' Eagle head on the bike with the rest of the bike painted black with orange details. We wanted people to automatically recognize the bike as a performance bike; therefore we wanted the Screamin' Eagle head to be a prominent piece on the bike.