The Milwaukee-Eight motor is still in its infancy, but, like any good parent, its owners want the best for their baby and will pay money to get it. Much like an actual baby, optimal breathing is pretty important when it comes to motors. The difference being you can’t shove one of those rubber nose plungers into your motor to make it breathe better.
What you can do is go out and get yourself a performance air cleaner, like the Screamin’ Eagle Heavy Breather we got our little mitts on for our 2017 Street Glide. It’s a quick-and-dirty installation that upgrades our oxygen intake, giving the Milwaukee-Eight more air to burn. We didn’t see a reason to have it look ugly, so while we were at it, we dressed up the new breather with the matching Screamin’ Eagle Billet Heavy Breather Trim.
Step 1: The Screamin’ Eagle Milwaukee-Eight Heavy Breather (part #29400264) comes complete with everything but the tools and the Loctite.
Step 2: The Screamin’ Eagle Billet Heavy Breather Trim Kit (part #61300688) is pretty simple: airbox cover, foam pad, airbox collar, and four #8-32 x 1.25-inch screws.
Step 3: By the time we got to the Harley-Davidson fleet center, shop boss Alan Barsi already had the stock breather assembly removed from the Street Glide.
Step 4: pHis first step is to join the kit’s throttle body to its backplate with the included self-tapping screws. He uses blue Loctite on all of the threaded fasteners for this project.
Step 5: After removing the backing from the induction module backplate gasket and installing it to the plate, Alan puts the rubber rings in place in the counterbore around the breather screw holes.
Step 6: Here, Alan screws the backing plate assembly onto the motor. A dab of blue Loctite goes onto each backplate mounting screw, they’re inserted through the plate to the module, and he twists each screw just enough to engage the threads of each of them.
Step 7: Now the larger O-rings are placed in the counterbore around the breather screw holes and Alan inserts the two breather screws then torques them down to 120–144 inch-pounds.
Step 8: He then pays a visit to the backplate mounting screws and tightens them down. He’s done this so many times he can practically do it by feel, but if you want to be more specific than that, tighten them to 55–60 inch-pounds.
Step 9: If we were just doing the Screamin’ Eagle breather kit, we’d install the air filter to the intake tube. Since we’re putting on the trim kit also, Alan opts to mount the intake tube to the bike without it because it’s easier that way. He lines up the holes of the gasket and the intake tube flange then secures the two parts to the backplate with the associated screws and tightens them down to 55–60 inch-pounds.
Step 10: Time to trim out the air cleaner element before it goes onto the bike. Alan puts the mounting ring over the filter’s band clamp cover first.
Step 11: There’s a foam disc that comes with the trim kit to help keep the air cleaner cover in place. After Alan removes the adhesive strip from the disc, he sticks it inside the small end of the cover then puts the air cleaner element inside.
Step 12: At this point, the mounting ring and the cover are secured using the four screws that came with the kit. Blue Loctite goes onto each one then each screw is tightened to 15 inch-pounds.
Step 13: Finally, the air cleaner element goes into its new home on our Street Glide. The clamp that came with the air cleaner/breather kit holds it to the intake tube. You’ll want to tighten the clamp around the element flange to 45–55 inch-pounds.
Step 14: Bam! All done. The Screamin’ Eagle Heavy Breather kit should give us extra grunt in the power department (we’ll know more when we dyno the bike). The blacked-out kit damn sure adds some angry aggression to the overall look of our Milwaukee-Eight motor.