The PowerPacc comes with everything...
The PowerPacc comes with everything you see here: a billet backing plate, a re-useable filter element, a billet snap in venturi, a pair of breathers, and all the necessary hardware.
If you could spend under $300 and less than an hour working on your bike to gain almost 10 lb-ft of torque, would you do it? Of course you would! Doherty Machine's PowerPacc air cleaner backing plate and filter combo is easy to install and the power gains are obvious right from idle to the middle of the powerband -- where you need it most. For this tech article, we used the kit for '93-or-later Evo-style Big Twins, but there are three other kits available that will fit almost any motor, including '84-'93 Evos, '91-and-later Sporties, and '99-and-later TC's.
Larry Hardy, the motor mastermind at Lifestyle Cycles in Anaheim, California, helped us out with the install.
 After tearing off the original...  After tearing off the original backing plate and air cleaner, we were left to work with an S&S E carburetor bolted to a hopped-up 97-inch S&S motor. |  We ran a couple of passes...  We ran a couple of passes on the dyno before the install for a baseline, and found that at 2,100 rpm, the motor was putting out about 74 lb-ft of torque and 30 hp. We were going to be getting more air into the motor, so we were going to need more fuel as well. Larry swapped out the main jet for the next size up. |  Larry dropped a bit of threadlocker...  Larry dropped a bit of threadlocker onto each bolt that secured the backing plate to the carb. |
 The head bolts that fasten...  The head bolts that fasten the backing plate to the heads were tightened down next. |  Firmly pressing the radiused...  Firmly pressing the radiused billet venturi is all it took to attach it to the backing plate. |  Then, the high-volume, washable...  Then, the high-volume, washable air filter went on the intake. |
 A little more threadlocker...  A little more threadlocker was placed on the air filter plate screws... |  ...and the air-filter was...  ...and the air-filter was wrenched in place. |  A single bolt is used to tighten...  A single bolt is used to tighten down the air cleaner cover. |
 Completely installed. With...  Completely installed. With Doherty's system you can go from the stock teardrop cover to a round-style cover without changing your carburetor. |  There was about an 11lb-ft...  There was about an 11lb-ft gain of torque and about a 5hp gain! Now the motor puts out 85lb-ft and 35hp at 2,100 rpm. | |