One of the first things a rider does to his or her new scoot is bolt on a new exhaust system. The stock exhaust systems on most of the new four-strokes are quite good since the manufacturers try endless variations before releasing a bike to the public. For aftermarket companies, it's simple to raise the bar as far as quality and weight go with trick materials and painstaking craftsmanship. But to completely blow away the stock system's performance and make the aftermarket model worth its princely price tag, they had better do their homework.
We opted to test two bikes: the most-popular motocross bike ever, the Honda CRF450R, and its new challenger, the long-awaited Suzuki RM-Z450. Both are incredible in stock trim, but we wanted to see how much we could improve the bikes. It mostly comes down to personal preference. In some cases, an aftermarket exhaust system may not generate much more sheer horsepower and torque but will boost it on different points of the power curve. Some exhausts offer more bottom and mid, while others more mid to top-end. Whatever power characteristics you are looking for in an engine, the exhaust system is a great way to coax out a curve to suit your riding style.
All the systems in this test worked surprisingly well, and the craftsmanship on all was incredible. We covered all bases by testing at three different tracks, making dyno runs, weighing the pipes and, more important, sound testing the exhausts. This last test scared away a few manufacturers, but sound requirements are very important and something Dirt Rider takes seriously. A few companies are missing from this comparison because either they didn't want to meet the AMA Pro Racing's 102-decibel limit we specified or they didn't have a product available at the time of testing. After weeks of punishing the parts, we compiled our results and were amazed with how close some of the systems are to each other. So read up and see which one is-or isn't-for you.
Test Notes
This test comprised high-end exhaust systems; chances are a given manufacturer makes a less-expensive version.
The sound test procedure was performed by Chemhelp's professionals (www.chemhelp.com) under controlled conditions. Chemhelp uses the same meters employed by the Forest Service, BLM and California State Park rangers, but these sound readings may vary in the field. We opted to go with AMA Pro Racing's 102-decibel standard.
Sound fact: Decibels are logarithmic and do not add directly; that is, two 80-decibel bikes do not produce 160 decibels but rather 83. Thus, as a very rough rule of thumb, reducing the sound of a bike by 3 decibels has about the same effect on the "acoustic environment" as cutting the number of off-road motorcycles present by half.
Testing Conditions
Where: Piru Motocross Park, I-5MX and Staben Ranch
Elevation: 500-3000 feet
Temperature: 68-75 degrees
Fuel: Pump
Jetting: Stock for both bikes
Overall score: Each rider rated each exhaust system on a scale of 1 to 100, then we combined all scores to reach an average. The stock system was used as our baseline to which every system was compared. Ratings were decided by track performance only.