According to Screamin’ Eagle press materials, the end user can expect approximately a 10% performance increase throughout the rpm range.
(Pro tip: Riders who forego the Pro Street Tuner are really more interested in the look and the sound of the intake and exhaust than they are in getting better performance out of their bike’s engine.) Stage II further enhances the Milwaukee-Eight’s ability to breathe by adding a choice of cams to the mix.
Stage III builds on the Stage I and Stage II kits by bumping the Milwaukee-Eight’s displacement from 107 c.i. In order to facilitate that increase, the kit includes: cylinders, high-compression aluminum-coated pistons, piston rings, a cam (different from either Stage II cam), valve springs, tappets, and all necessary gaskets.
When discussing this article with E-i-C Duke, he asked me why, if the changes were so easy to make, didn’t H-D just make the original equipment deliver this kind of power. First, the MSRP would likely go up with these components being standard, and the increase might deter some potential buyers from signing on the dotted line.
Second, motorcyclists like to make changes to their bikes.
Stage I is the least expensive and incorporates the two aftermarket parts that most motorcyclists put on their bikes: intake and exhaust.
Using the 2017 Road Glide as an example, the Street Cannon Performance Slip-On Mufflers will retail for $499.95, and the Heavy Breather Performance Air Cleaner takes care of the intake for $399.95.
The Stage III upgrades, with their $1,595.95 price, are as far as the Milwaukee-Eight can be taken – for now.