After logging some break in miles on the freshly built engine, we headed back to Bennett’s Performance for some fine-tuning on the dyno. Using 12 discs on each SuperTrapp muffler and a 160mm main jet on the Mikuni 42mm carb, the Sweet Tracker produced 72.23 hp and 73.73 lb-ft of torque–which based on a previous 1,200cc conversion we did—a stock 883cc engine produced somewhere around 43hp and 43 lb-ft of torque. So this was an increase of 29.23 hp and 30 lb-ft of torque over stock.
Eric felt that the Mikuni carburetor needed a little more fuel, so he swapped out the stock main jet from 160mm to 165mm. Eric also adjusted the ignition mode from single-fire, single-spark to single-fire, multi-spark and kicked the advance slope from two to six just to see what would happen. Lastly, he removed all the discs from the SuperTrapp exhaust pipes to see the other end of the spectrum. The second pull on the dyno produced 80.08hp and 80.39 lb-ft of torque, a nice increase with just a few modifications. But as you can see, there’s some dips in the hp and tq curves starting around 3,000 rpm.
SuperTrapp sent out a set of its open end caps for testing purposes (each end cap equates to about 10 discs). We installed six regular discs and one open end cap in each muffler (approximately 16 discs), and added even more fuel by swapping the 165mm main jet to a 170mm main jet. Lastly, Eric installed a different backplate his neighbors at Branch O’Keefe recommended we try. The backplate has a custom-made venturi that allows air to flow more optimally and not at such a drastic angle.
After all the tweaking and tuning, Eric and I were confident that the Sweet Tracker would be where it needed to be for this dyno run. We were right. The end result yielded 84.14 hp and 78.95 lb-ft of torque. If you look at the difference in all three graphs, you'll notice the power and torque curves in this graph are smooth and continue to climb all the way through the high rpm band. With an increase in horsepower of 95.7 percent and torque output of 83.6 percent, it's safe to say these components performed well aboce our expectations.
If you’ve been following the Sweet Tracker build over the course of the year in HOT BIKE, we went from the mild stock version of a 2000 XL883 Hugger Sportster to a wild Sweet Tracker with help from various companies making the project possible. Last month we wrapped up the two-part engine performance upgrade where we swapped the stock 883cc cylinders and pistons with Revolution Performance 1,250cc cylinders, larger pistons, and then sent the stock 883cc heads to RevPerf to be ported and polished. We also installed Screamin’ Eagle .536 lift cams, SuperTrapp XR style 2-into-2 pipes, Daytona Twin-Tec 1005S-EX Ignition system, and a Mikuni 42mm Easy Carb kit.
Getting these top-of-the-line components to work in perfect harmony is a feat in and of itself and Eric Bennett from Bennett’s Performance in Signal Hill, California, is quite the Harley tuner. He and his in-house dyno are up to the challenge of making the most power out of an air-cooled engine whatever the configuration.** HB**
(562) 498-1819 | bennettsperformanceinc.com