Yamaha Road Star 1600 Intake Supercharger - Motorcycle Hop-Up

Gifts from the motorcycle horsepower gods for Yamaha's Road Star. Fom the April 2000 issue of Motorcycle Cruiser magazine. By Evans Brafield

Most cruiser riders just can't leave well enough alone. What's the first thing most enthusiasts do after buying a new cruiser? Ride it home, remove a perfectly good part from the shiny new machine, and replace it with a prettier piece of chrome or leather. Admit it, we've all been guilty of this little transgression, haven't we? Don't worry, we understand. Really. This compulsion is beyond human control, as if we receive some higher calling to customize our motorcycles.

And then there's the draw that horsepower exerts on all motorcycling believers. Some riders claim they purchased that aftermarket pipe for a little more "rumble." But we know what they were really searching for: Grunt, oomph, get-up-and-go, or just plain horsepower -- the Holy Grail of motorcycling, the substance that the High Priests of Tuning spend a lifetime studying yet never get to hold in their hands.

So, what route should we follow during our pilgrimage to the Temple of Torque? What kind of offerings should we bring? Rest assured fellow seekers, your questions will be answered.

The Steps to Enlightenment

Our long-term Yamaha Road Star cranked out 58.2 horsepower and 90.7 ft-lbs of torque at the rear wheel in its stock form. To this we added a Roadhouse classic exhaust system ($569) for its unique, retro styling, good breathing, and socially conscious volume. Next, we installed a Dynatek Dyna 2000 ignition system to raise the ultra-conservative OE rev limit from 4200 to 5000 rpm. While the adjustable rev limit is essential, the Dyna 2000's variable ignition also allows the advance curves to be adjusted to the engine's state of tune. Since we're planning an exhaustive aftermarket pipe comparison in a future issue, we skipped over the pipe/jet kit stage of performance and jumped straight into intake kits. All of dyno runs were conducted on the Bartels Dynojet Dynamometer.

Baron's Big Air Kit

The detail work of the $200 Big Air Kit is visible at a glance. The chrome billet air cleaner cover is flawless. The K&N; air filter provides no-nonsense breathing. The brackets attaching the composite backing plate to the engine also wear a layer of chrome. Less visible details include: allen bolts to replace the easily stripped phillips-head float-bowl screws, a titanium needle, and a variety of jets hand-picked for each customer's application (based on average altitude, humidity, and temperature). Installation takes a little over an hour.

The engine started immediately, revving quicker and more cleanly thanks to the less restrictive intake. Peak torque increased to 97.0 ft-lbs -- a 6.1 ft-lb (6.7 percent) bump. The beefed-up horsepower curve surpasses the stock numbers throughout the entire range, peaking 2.8 horsepower (4.8 percent) higher at 61.0 horsepower. Road Stars outfitted with this kit may generate even better numbers since the Big Air Kit was tested on a rainy day with 100 percent humidity -- not the recipe for strong runs. The Dynatek ignition allows riders to use this top end increase by cutting out the spark after the power has started to taper off, instead of right at peak power as with the OE ignition.

Riding around town, our Road Star has more pull off the line -- thanks, no doubt, to the broader torque curve. Ridability is seamless throughout the rpm range without a single hiccup. Roll-on power is noticeably stronger in passing maneuvers.

Thunder Manufacturing's Thunder Air Kit

The Thunder Air Kit can be configured with a variety of intakes. We selected the $278 teardrop intake kit. The fluted chrome billet cover and billet backing plate sandwich a K&N; filter, forming a sturdy assembly. Although the mounting brackets are not chromed, the kit looks quite nice when mounted on our Road Star. The thorough instructions detail the installation procedures and recommend which of the included jets should be utilized in various applications. Allow an hour to install this kit.

The ride to the dyno on our hopped-up Star had us grinning. Response to throttle inputs at any rpm was immediate and strong. Even with the raised rev limit, the shift to second off the line had to be handled quickly to avoid tapping the limiter. We knew both the torque and horsepower curves had improved a bunch, but we didn't know what the numbers would reveal. Peak torque jumped 9.9 ft-lbs and broke into the triple digits at 100.6 ft-lbs. The top-end power improved 5.7 horsepower to 63.9 horsepower. Both the torque and horsepower curves are broader than stock at their peaks with no flat spots.

A Higher Plane

While we felt the intake kits had given impressive results, we knew there was more power hidden in the depths of our Road Star engine. We'd heard of two companies with engine kits that were purported to give the type of power gains we were looking to gain. Although Patrick Racing has an engine kit, the company was unable to deliver a working example within our time constraints. We hope to sample these engine mods in the future. Baron Custom Accessories was able to bring us an example of its engine kit -- in the form of Shooting Star, the cover bike from our February 2000 issue.

The Baron Road Star High-Compression Piston Kit ($339) consists of high compression pistons, and a ported and flowed head (an optional $675 service). From the moment the engine barks to life, it is obvious that this is not a normal Road Star. Even so, we couldn't have predicted the incredible dyno numbers. Torque peaks at a whopping 106.7 ft-lbs and stays above 100 ft-lbs from 2000 to 3000 rpm! Horsepower tops out at 73.0 horsepower. The horsepower curve has an impressively broad plateau, running above 70.0 horsepower from 4000 to 4750 rpm. What makes this accomplishment even more surprising is that Shooting Star still runs a stock carb! While it's hard to consider a 40mm carb restrictive, in this case, the throttle body may need to be enlarged to 45mm for the engine to reach its full potential -- perhaps in the range of 80.0 horsepower! This High-Compression Piston Kit should be available from Baron by the time this issue arrives in newsstands.

V-Twin Valhalla

In the search for more horsepower, nothing exceeds like excess. Baron, in conjunction with MagnaCharger, is currently developing a bolt-on supercharger kit for the Road Star. When we were arranging for a Big Air Kit for this article, we were asked if we were interested in testing a prototype of the Road Star supercharger system. Remembering the fun we had the last time we threw a leg over a supercharged cruiser (December 1997), we accepted immediately.

The Baron test mule uses a supercharger set at only five pounds of boost (to allow the use of pump gas) and a Dyna 2000 ignition. It still has the stock carburetor and pipes. But as soon as the engine bursts to life, there's no doubt that it will make serious power. The supercharger adds a menacing mechanical overtone to the engine -- like gnashing teeth. The engine wants to rip up the pavement. However, once on the road, our supercharged Star didn't feel terribly fast -- until the pilot looks at the speedometer. The almost linear horsepower curve and flat torque curve (except for a midrange dip) conspire to take away the impression of acceleration.

The dyno numbers tell a different story, however. The torque peaks at a respectable 95.7 ft-lbs, but even running at five pounds of boost and with some midrange jetting problems, the torque output stays above 90.0 ft-lbs until 4500 rpm! Horsepower keeps climbing all the way to the rev limit, peaking at 77.3 horsepower. These numbers are definitely food of the gods. When the prototyping is finished and jetting finalized, even bigger numbers should pour out of this setup. Imagine installing a free breathing carburetor and pipe then bumping up the boost. We know we're not the only ones thinking this way since Baron currently has almost 20 preorders for this $2600 (approximate) supercharger kit.

So, there we have it, brothers and sisters: enlightenment through higher horsepower. The gods have been good to us. Now, go out and spread the good word. You will know that others have traveled the same path before you when you see black stripes in the road.


Baron Custom**
Accessories, Inc.
550 Industrial Way, Suite E
Fallbrook, CA 92028
(760) 731-1200

** 164 South Valencia St.
Glendora, CA 91741
(626) 963-1669

** 60 West Easy St. #6
Simi Valley, CA 93065
(818) 707-1276

**Thunder Manufacturing
** 4210 N. 39th Ave.
Phoenix, AZ 85019
(602) 269-5033

Evans Brasfield is a former staff editor for _Motorcycle Cruiser and sister title_ Sport Rider _magazine. He is now a freelancer, and has _ his own website.

For more articles on custom bikes and articles about how to customize and modify your motorcycle, see the Custom section of MotorcycleCruiser.com.

Photography by Dean Groover
Beauty and brawn, too. Shooting Star is the prettiest test mule we've seen. The dyno sheet tells the story of beauty being more than skin deep.
Hiding behind the Baron Big Air Kit's chromed slab of billet aluminum, a K&N; air filter keeps out contaminants while assisting the engine in its attempt to rid the area of its atmosphere.
The Thunder Air Kit also turns to K&N; filtration for the free-flowing, clean air necessary to get the most out of proprietary jetting.
The Thunder Kit (yellow) is clearly the victor on the dyno, though Baron's kit (green) still offers a healthy jump from stock (blue). In general, air kits are the best first power mod, stronger and quieter than a pipe. Click for larger chart with legend.
A Dynatek ignition is a Road Star must-have. The Dyna 2000 allows rev-limit and advance-curve adjustment.
Although we're still not sure if superchargers suck or blow, we do know that they put out great power. Only three hours of wrenching enabled our Road Star to crank 77.3 horsepower out the rear wheel.
This dyno chart shows how Shooting Star (yellow) and the Supercharged engine (green) compare to stock.