Motorcycle.com

Right, the all-new Harley-Davidson Street 750 didn’t win our recent Millennial Hep Cat Shootout, but its engine sure did: 53.5 horsepower at 7900 rpm is way more than the 40.6 (at 6500) produced by the Moto Guzzi V7 Stone that won the overall event.

Discuss this at our HD Street Forum.

Even the youngsters who came into the thing prepared to dislike the Harley were bowled over by its happy, free-revving V-Twin, but slightly disappointed to not set off any car alarms at all. Playing to its strength, then, and satisfying our own need to never leave well enough alone, we turned to the H-D Parts & Accessories catalog to see if we could make things even better and just slightly louder.

Yup, there it is, the Nightstick Slip-On Muffler is exactly what its name suggests. Installation appears to be the proverbial snap, though we wouldn’t know since H-D doesn’t want idiot journalists wrenching on its bikes, so they did the deed for us at its fleet center. Looks like you loosen the two lovely stainless hose clamps that hold on the rear section of black heat shield, remove it, then loosen the exhaust clamp that holds the stock muffler on and replace it with the Nightstick. The Nightstick is steel, like the stocker, and doesn’t remove much, if any, weight. It comes with eight Supertrapp-style diffuser discs bolted to its business end, and is supposed to flow more air than the stocker, of course, while still conforming to federal and California Air Resource Board (CARB) requirements, a delicate balance indeed …

Taking advantage of greater exhaust flow capability means inhaling more air, which is achieved with the SE Performance Air Cleaner Kit, which consists of a higher-flowing oiled-cotton filter that’s washable and reusable, and the hardware needed to use it with the standard air cleaner housing.

None of that’s going to do you any good without the H-D Stage 1 ECM recalibration, which my local Orange County, CA, dealers will do for around $200. There are other ways to do it than the H-D service department, but none are less expensive and most will void your warranty. The reflash, of course, programs the bike’s computer to give the engine fuel commensurate with its new airflow. It also extends the rev ceiling from just below 8000 rpm to 8500.

Dyno courtesy of MotoGPWerks

Looking at the dyno chart will be more than a little underwhelming for those who’ve just shelled out $700, almost 10-percent of the cost of the bike, to gain less than one hp and one lb-ft of torque. But what you can’t see is the snappier, more immediate throttle response at all rpm. You also get a burlier exhaust note that’s still far from obnoxious. Critically, stacking more diffuser discs on the Nightstick will result in more flow, noise and power, up to a point where the Stage 1 reflash will no longer be able to keep up – but we’re not allowed to tamper, so we didn’t. (An anti-tamper Allen bolt in one of the disc holes removed all temptation.) But it seems like my old SRX-6 used to have about twice that many discs.

Finally, our fuel mileage went from 41 to 45 mpg, which is nice, and tells us we’re achieving the same speeds with smaller throttle openings. Not that we ever use small throttle openings on the Street. It’s a great bike.

Tune in next time, when we see if SBS brake pads are any help for its really too-weak front brake. Fingers crossed …

Screamin’ Eagle Nightstick 2-into-1 Slip-On
Part Number 64900220
$349.95

Screamin’ Eagle Performance Air Cleaner Kit
Part Number 29400197
$79.95

Stage 1 ECM Recalibration at your H-D dealer
$200 approx.