Motorcycle Exhaust-System Comparison: Pipes for Kawasaki Big Twins

Seven exhaust systems for the Kawasaki Vulcan 1500 go header to header on the dyno, scales and decibel meter. From the February 1997 issue of Motorcycle Cruiser.

Almost one fourth of the people who responded to the reader survey in our first issue said they planned to buy an exhaust system for their bike in the next year. If you apply this percentage across the entire cruiser market, you begin to understand how a representative of an aftermarket company that makes top-quality accessories for cruisers could say that, even with all their billet products, the single largest portion of their business still comes from pipes.

Being curious folks, we decided to see what pipes were available for our long-term Vulcan 1500 Classic at the tail end of The Year of the Cruiser. The results of our initial query of pipe manufacturers illustrated two facts we were already aware of. First, with six manufacturers sending us pipes for a bike that has been on the market for less than a year, we can confidently say that there are more exhaust customizing options than ever available in the Japanese cruiser market. Second, since half of the pipes we tested were either pre-production or first-run production items, things weren't always so rosy in this segment of the market. These thoughts lead us to wonder how these pipes would compare to each other, how well thought-out they were, and if they would fulfill the conflicting demands of good power and good citizenship.

White Brothers of Yorba Linda, California, which sells some of these brands of pipes itself, was kind enough to provide its DynoJet dynamometer for the horsepower numbers and R&D; Mechanic Dennis Emerson for the wrenching and installation advice and expert commentary. We timed each installation and rated it on a scale of one to five, with five being a perfect score. Next, we ran the bike on the dyno to figure the vital stats. All the pipe manufacturers, with the exception of Cobra, which sells its own jet kit, recommended using a DynoJet jet kit with their pipes. We tested each pipes with the jet kit requested.

Sound levels were tested at the AMA standard of 20 inches at 45-degree angle from the pipe opening with the sound meter facing away from the pipe and the engine at a constant 3000 rpm. The drive-by sound test was taken at a distance of 12 feet with the Classic driving by at a constant 45 mph in second gear, which translates to about 3000 rpm in the real world. Decibels are calculated on a logarithmic scale which means that if a sound increases by 10 decibels, it's three times as loud. An increase of 20 decibels translates to almost 10 times louder. Since our sister publications Motorcyclist and Sport Rider established 104 decibels as their maximum acceptable sound level for street use, we decided to maintain the same limit for our test. Though it's a bit arbitrary, going above guarantees that you are making enemies for motorcycling every time you ride your bike.

How did the pipes perform? All of the pipes weighed in less than the stocker -- some by as much as 20 pounds. All made more power. All were louder than stock, but some were unacceptably so. Most of the headers blued, a problem caused at least partially by running the bike at full throttle on the dyno immediately after installing the pipes. While several of the pipes' heat shields did a good job of hiding the blue, taking new pipes through a couple short, reduced-heat cycles before getting them thoroughly warm may reduce bluing. Finally, some of the pipes limited ground clearance.

Note that just changing the jet kit improves power significantly. It also improves driveability somewhat, even on the 1500 Vulcan Classic, which is already very good in stock form. If the power increases these pipes offer aren't enough for you, Emerson suggests removing some of the intake plumbing and adding a K&N; air filter.

Stock System
Staggered duals, $NA, 33.5 lb

Installation time/ease: 1 hour / 3 points
Peak horsepower: 48.1@4500 rpm
Peak torque (ft.-lb): 71.3@2500 rpm
Sound level at 20 in.: 92 db
Sound level rolling: 81db

The factory exhaust system has the unenviable job of meeting EPA requirements while providing an appealing exhaust note, appearance and performance. Only in the power department does Kawasaki's compromise make itself noticeable. However, the huge performance gains of yesteryear are no longer achieved by simply bolting on a pipe; OEM units are too well designed. Aftermarket pipes now offer more moderate gains, the opportunity to customize, and instant weight loss. At 33 pounds, 8 ounces, the stock pipe is a porker. Much of this comes from the expansion chamber under the swingarm.

To see how much power came from the pipes and not the jet kit, we ran the stock exhaust with both the stock and DynoJet jets. The DynoJet kit yielded 1.2 horsepower (49.3 peak) over stock jets, and improved throttle response as well.

One note about removal: If the system is hot (and who would remove a hot pipe but people who have six more to put on and test), you run the risk of shearing off the studs connecting the headers to the expansion chamber. The complexity also makes it a bear to put back on.

Cobra
Classic Slash-Cut, $380, 12.8 lb.

Installation time/ease: 50 min. / 3 points
Peak horsepower: 51.8@4500 rpm
Peak torque (ft.-lb): 72.8@3000 rpm
Sound level at 20 in.: 103 db
Sound level rolling: 90 db

Initially, we wondered why Cobra would sell the Classic slash-cut exhaust system with only three little heat shields, but Cobra has since expanded the pipe kit to include full-coverage heat shields, which were formerly sold as an option. The full shields protect the rider from heat and hide the top part of the header where chrome pipes are prone to bluing.

Installing the Cobra pipes took time because of tight clearance between the rear cylinder's canister and the rear axle. After trying several methods, we bent the pipe's bracket outward to gain more clearance. Cobra provides a bracket to move the voltage regulator (which hangs under the swingarm to hide the ugly expansion chamber on the stock pipe) to a less-visible location, cleaning up the left side.

The Cobra system ranked in the middle of all the categories we tested, providing a decent power increase without crossing over our maximum streetable loudness. Combined with a Cobra-assembled DynoJet kit, the Cobra pipes produced a maximum of 51.8 horsepower and 103 decibels. The only difference between the kits is Cobra's DJ132 main jet versus DynoJet's DJ136 main jet.

DG
Slash-cut staggered dual, $300, 19 lb.

Installation time/ease: 10 minutes / 5 points
Peak horsepower: 49.0@4700 rpm
Peak torque (ft.-lb): 72.300@2000 rpm
Sound level at 20 in.: 99 db
Sound level rolling: 89 db

The DG Hard-Krome staggered duals were the easiest pipes to install, bolting on in a mere 10 minutes. The double-wall pipes have a built-in heat shield, which protects both rider and passenger from burns. Observers liked how the thick pipes added to the Classic's fat look, tying with the Vance & Hines pipes in our garage beauty pageant. One miscue in the pipes' fit and finish was that the welds between one pipe's header and canister were not ground down prior to chroming, leaving an ugly seam. While tipping the scales at 20 pounds 8 ounces, it was the heaviest of the aftermarket pipes, but it still shaves over 13 pounds off the Classic.

The DG pipes were the least powerful of the aftermarket units tested, making only 49.0 horsepower, a scant 0.9 more than the stock pipe. Being more restrictive than the other pipes we ran with the DynoJet kit, the DG pipes would benefit from additional jetting work to bring out more power. Incorporating an internal tapered head pipe that gradually funnels into 2.5-inch-diameter tubing, the DG pipes' 99-decibel reading earns it the good-citizen award of the test.

Samson
Fishtails, $280, 10.6 lb.

Installation time/ease: 35 minutes / 3 points
Peak horsepower: 51.7@4500 rpm
Peak torque (ft.-lb): 74.8@1500 rpm
Sound level at 20 in.: 107 db
Sound level rolling: 95 db

Although we asked all six of the exhaust-system manufacturers to send us fishtail-style mufflers, Samson was the only manufacturer to actually send one. Unfortunately, Samson may have been penalized in the loudness comparison as a result. Pushing the sound meter to 107 decibels, the Samson exhaust pipes tie for worst in the sound department. These pipes are too loud for the street and were only ridden for photos and then removed. Delivering 51.7 horsepower--middle of the road in this comparison--we expected more output from all the racket.

Installation was straightforward and quick, even with the Spartan instructions. Be sure you have American tools (1/2- and a 9/16-inch wrenches) because no metric bolts are supplied.

When viewing the pipe from the side, people either loved or hated the pipe's long skinny look, which was accentuated by the lack of a heat shield. However, most agreed that the fishtails looked cool from behind the bike. Optional head shields are available from Samson.

SuperTrapp
StreetCruiser system, $550, 10.7 lb.

Installation time/ease: 2.5 hours / 2 points
Peak horsepower: 53.7@5000 rpm
Peak torque (ft.-lb): 72,3@2200 rpm
Sound level at 20 in.: 102 db
Sound level rolling: 89 db

Except for technical problems in our first day of dyno testing, the SuperTrapp exhaust wouldn't have arrived in time to be included. Arriving late, these pipes exhibited typical preproduction problems: visible welds, no heat shields, brackets that didn't fit. One header was about 2.5 inches too long, and both headers had to be modified slightly to seal leaks between the headers and canisters. The preproduction bugaboos made installation time the longest of any pipe here.

The stainless-steel system yellowed immediately, but we don't expect the production units to suffer from this problem. The pipes feature the SuperTrapp megaphone design that people either love or hate. The droopy lower canister dragged easily.

Despite all the problems, the SuperTrapp Street Cruiser system, which runs 12 disks per canister, put out 53.7 horsepower--just 0.1 short of the best--and stayed within our noise limits at 102 decibels. Installing additional disks would presumably yield more power and more noise. Of course, the production version may be even better.

Two Brothers Racing
Slash-cut dualies, $450, 15.6 lb.

Installation time/ease: 45 minutes / 4.5 points
Peak horsepower: 53.8@4500 rpm
Peak torque (ft.-lb): 74.3@2100 rpm
Sound level at 20 in.:108 db
Sound level rolling: 94 db

Our Two Brothers slash-cut duals were the first set the firm built for the 1500 Classic and were rushed to reach us in time for this test. As a result, they suffered from many of the problems a first-production piece has. No instructions were included, but we've been assured that instructions will come with the pipes sent out to customers. All of the mounting bolts were too long. Flange nuts were not included. The middle bracket of the front pipe could not be held in place with the stock bolts, but Emerson said he didn't think the bracket was necessary.

The Two Brothers pipes produced the most horsepower, delivering 53.8 horsepower at 4500 rpm. However, the pipes also tied for the dubious honor of being the loudest even though the exhaust note never felt as extreme to our ears as the Samson pipes. Nonetheless, at a roaring 108 decibels, these pipes are much too loud for the street. Remember, if a pipe is so loud that you don't want to open the throttle for fear of a ticket, you can't use the extra power.

Vance & Hines
Classic dual, $499, 21.9 lb.

Installation time/ease: 1 hour / 4 points
Peak horsepower: 52.5@4500 rpm
Peak torque (ft.-lb): 73.4@1700 rpm
Sound level at 20 in.: 102 db
Sound level rolling: 87 db

The Vance & Hines Classic Duals came with no less than five stickers plastered on them warning that ground clearance may be reduced. Ironically, we didn't drag these pipes when riding. Installation was relatively glitch-free, but we did need to supply our own flange nuts for the headers. The pipe clamps are thinner than stock, causing the stock, capped flange nuts to bottom-out before the clamps were tight. Relocating the voltage regulator under the swingarm was a bit time consuming, but certainly cleans up the left side of the bike. Since the relocation is for purely cosmetic reasons, a note stating the optional nature of the relocation might be helpful.

In our garage sampling of opinions, the Vance & Hines pipe tied as the best looking of the bunch. The powerful VHR pipes scored a solid 52.5 horsepower--near the top of the class, and its 102-decibel reading placed the pipe in the street-reasonable category.

RESOURCES

Cobra Engineering
4915 E. Hunter
Anaheim, CA 92807
(714)779-7798
www.cobrausa.com

DynoJet Research
200 Arden Dr.
Belgrade, MT 59714
(800)992-4993 or (406)388-4993
www.dynojet.com

Samson Motorcycle Products
270 S. Loara St.
Anaheim, CA 92802
(888)572-6766 or (714)518-2480
www.samsonusa.com

SuperTrapp/Kerker
4540 W. 160th St.
Cleveland, OH 44135
(216)265-8400
www.supertrapp.com

Two Brothers Racing
1715 E. Wilshire Ave., No. 701
Santa Ana, CA 92705
(714)550-6070
www.twobros.com

Vance & Hines
14010 Marquardt
Santa Fe Springs, CA 90670
(562)921-7461
www.vanceandhines.com

For additional evaluations of, comparisons of, and shopping advice for motorcycle gear and accessories, see the Accessories and Gear section of MotorcycleCruiser.com.

Most pipe makers recommended a DynoJet kit to adjust mixture.
The big expansion chamber in the stock pipe adds weight and cost, but it helps make power with minimal noise.