Two Brothers Racing's Double-Supercharged Honda Valkyrie

Sometimes one supercharger just ain't enough for one motorcycle. From the December 1997 issue of Motorcycle Cruiser magazine.

Picture this: A Honda Valkyrie, the powerhouse of the cruiser world, force-fed about 210 cubic feet per minute of the local atmosphere, which is combined with super unleaded, ignited, and spewed out through six barely baffled chrome pipes. How does 138 horsepower grab ya? Somewhere south of the border, most likely. When we heard that Craig Erion, owner of Two Brothers Racing, was building a dual-supercharged Valkyrie, we began an unrelenting campaign to ride it. After enduring months of pestering, Erion agreed to let us take his Valkyrie home. We could barely contain our glee.

A year before, Erion started thinking about his fantasy bike. He'd always felt that the Valkyrie, with its big, naked engine, was styled after hot rods of the 1950's and decided to take the street-rod concept to its natural extreme. Superchargers were the only way to go. However, he didn't want the Valkyrie to become some muscle-bound show bike that couldn't be run without the risk of a sudden, dramatic failure. "The Valkyrie," according to Erion, "is a real rider's bike. Even with the superchargers, this bike had to be streetable."

To achieve his goal of excessive-yet-streetable power, Erion turned to Richard Sims of Sims Engineering. Sims, a veteran horsepower junkie and supercharger guru, took two Magnacharger 60-cubic-inch roots-type superchargers and began to work his magic. The Magnachargers receive their drive power from the crankshaft via a snazzy belt system. Sims designed and STX Welding fabricated the manifolds that connect each supercharger to its very own billet-air-cleaner-topped Weber 40mm DCOE dual-throat, downdraft carburetor on one side, and the intake ports on the other. Regulating the boost pressure and, in this case, keeping the boost down to a reasonable 4 psi, Sims Engineering's pop off valves allow excess boost pressure to be bled off back into the atmosphere. Sims says he kept the boost low to maintain optimum reliabiltiy from the engine. Once the boost crossed the threshold of five or six pounds of boost, he'd be concerned about the possibility of detonation with pump gasoline. A slippery slope of lower compression pistons, black box alterations, and other engine modifications would soon follow any increased boost. The four pounds of boost still allows over 25 percent more fuel/air mixture to enter the cylinders--more than enough for street use.

One problem Erion and company had to surmount was the radiator's interference with the supercharger drive belt. The space under the tank that had formerly housed the stock intake and EPA plumbing was vacant and two Goldwing radiators from Honda Kawasaki Sportcenter moved in. The radiators were modified and mounted with STX's brackets and piping. Although the radiators are mounted sideways to the airflow, enough air rushes in between the two radiators at speed to keep things cool. At city traffic velocities, the Valkyrie's stock fan draws air in through one radiator and blows it out through the other--not the most efficient method but effective enough so far. Now the front of the engine is uncluttered, with the exception of the nasty belt.

Once Sims finished dyno tuning the Webers, Erion felt the stock ignition system wasn't throwing enough juice into the mix. A Nology ignition booster, high performance coils, and high tension leads (each with their own grounding wire attached to the engine block) were attached to a set of Denso California's non-resistor spark plugs. Now, Erion grins, the deposits on the plugs are nice and white, not black and sooty. The by-products of all the excitement exit with quite a bit of fanfare through a set of Two Brothers popular six-into-six pipes.

But a brute of a powerplant would be nothing without some cosmetic flair to hold the package together. The impossible-to-ignore, fire-engine-red paint was laid on by Paint'n Place. The wheels were polished and the cut out sections were powder coated red. Progressive Suspension supports both the front and rear ends of the bike. Custom enclosed air shocks are as striking (the enclosures are machined aluminum and match the texture of the fork) as they are effective. The fork springs are firmer than the stockers. Galfer stainless steel brake lines and pads help the binders scrub off all the excess speed the blown motor digs out of the pavement.

Weekend Concepts' spotlights and turn signals are surprisingly bright for such small items. These lights are sold as a kit with the mounting brackets from Two Brothers. The fat Bridgestone R701 front and R702 radial tires round out the Valkyrie's bad-ass appearance.

Thumbing the starter button elicits a bark from the six pipes. Within a second of hearing the engine for the first time, we understood why Erion named the bike "Odin: King of all Valkyries." Once settled into a lumpy idle, the rumble of the vanes rotating inside the supercharger combined with the wet sucking sounds emanating from the carburetors gives the impression of something that is mechanical yet very much alive. Blip the throttle and the engine responds with a bellow. Clearly, Odin is not one to be trifled with.

Trundling around town in low gears reveals the well balanced character of any other Valkyrie -- until the butterflies get cracked. Odin's pilot learns quickly that smooth control of the throttle is necessary at low speeds. Abrupt throttle inputs are redirected -- exponentially--back at the rider, who had better be leaning forward with a firm grip on the handlebar. At any speed, cranking on the throttle rewarded us with vision blurred by acceleration. However, at interstate speeds the throttle couldn't be whacked open but instead needed a quick roll-on to deliver maximum acceleration without a slight stumble. Off the line, the bike leaps forward with an intensity that is unfathomable to those who've never experienced a supercharged bike. Both Sims and Erion said Odin produces enough power to lift the front wheel of this 700-pound motorcycle in both first or second gears! While we didn't wheelie Odin, we did partake in enough burnouts (strictly for photo purposes, of course) to require replacement of the rear Bridgestone before our trip to the drag strip.

Our morning at LA County Raceway was unlike any other quarter mile we've experienced. With so much power down low in the rpm range, modulating the wheel spin proved to be the most difficult part of clicking off a quick time. The shift from first to second came almost immediately after the launch. Our best time was 11.42 seconds at 116.2 MPH (compared to the stock Valkyrie's 12.12 seconds at 107.0 MPH). We're certain that if piloted by someone with years of drag racing experience, the elapsed time would drop further.

In our short time with Odin, we rode the bike around town, on the highway, and on twisty roads. We even commuted on it! No other bike we've ever ridden got more reactions than this Valkyrie. Yes, it was really loud (imagine a dragster pulling up next to you on your way to work), and that would make people turn their heads. However, the reactions we'll remember are the people hanging out of their car windows to get a better look or the guy who pulled up next to the bike at three stop lights in a row. He'd give the universal signal for twist the loud handle, and every time we obliged him, he threw his head back and laughed. What we'll remember the most fondly is the feeling of our arms staining against the rush of Odin's acceleration.


1 Bridgestone Park
Nashville, TN 37214

Denso California
1201 Garden Lane
Sebastopol, CA 95472
(707) 823-9002

6788 Dawson Ave.
Goleta, CA 93117

Honda Kawasaki Sportcenter
24417 Rockfield
Lake Forest, CA 92630
(714) 859-3186

Kisan Technologies, Inc.
150 S. Wolfe Rd.
Synnyvale, CA 94086

National Cycle
2200 Maywood Dr.
Maywood, IL 60153

Nology Engineering
7360 Trade St.
San Diego, CA 92121
(619) 578-4688

Paint'n Place
847 S. Kraemer
Placentia, CA 92670
(714) 630-6326

Progressive Suspension
11129 G Ave.
Hesperia, CA 92345
(760) 948-4012

Sims Engineering
8295 Marek Rd.
Los Molinas, CA 96055
(916) 384-1739

STX Welding
12701 Lewis St., Suite 52
Garden Grove, CA 92840
(714) 750-4032

Two Brothers Racing
1715 E Wilshire Ave.
Bldg. 701
Santa Ana, CA 92705
(714) 550-6070

Weekend Concepts
3400 E. 69th St.
Long Beach, CA 90805
(562) 634-3783

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

The Magnachargers and associated hardware aren't the only cool things on this bike. The TBR light bar and National Cycle's Flyscreen add to the purposeful look.
And you thought the stock Valkyrie had a wide engine! The twin superchargers pump up the bike's looks in a way that's impossible to ignore.