Motorcycle Music by Eric Frank

If summer time in your town is anything like mine, it's full of BBQ, baseball and fireworks. Around my neck of the woods, it's hard to imagine any of those activities without hearing the dull (or sometimes obtrusive) roar of motorcycles. As a motorcycle rider, I have to admit, there's a fine line between the rich, mellow, powerful sound of a bike, and the sound of one that's blasting out of the pipes, trying to turn heads. Many people don't realize the performance drawbacks to such a blaring sound.

What's the first thing you do when you buy a shiny new cruiser right off the showroom floor? You make it loud enough to make your buddies laugh and babies cry! The easiest way to do this is with straight pipes. By modifying the stock exhaust, or replacing it with a set of one of the many aftermarket pipes available, you can get a nice custom sound.

But what if that's just not enough? What about those of us who tinker with bikes as an experiment in obnoxiousness?

To really make a statement, take all mufflers or baffles out of the exhaust for unrestricted flow from the cylinder port all the way to the end of the pipe. Sounds pretty easy right? Maybe a little too easy. A lot of people equate loud to fast, but this usually isn't the case.

Having true straight pipes and having no-restriction-baffles are two different things.

The common 2 cylinder (V-Twin) engine (found in many small and mid-size cruisers) needs that restriction to function properly. The presence of restriction sends a negative pulse back to the engine cylinder to scavenge any residual exhaust gases that may be lingering. Without this pulse, the engine just doesn't run right, and will most likely lead to loss of low-end power and/or premature failure. On the other hand, newer aftermarket exhausts, not only have baffles or mufflers to create this restriction, but also use a non-uniform pipe cross section that acts as an expansion chamber. This serves the purpose of introducing a negative pulse (previously noted). But you're not out of the woods yet! The air/fuel mixture also needs to be balanced (by re-jetting the carburetor) to find the optimal running conditions.

For those who waive fists at deafening two-wheelers as they roll through and disrupt picnics and catnaps, keep in mind that unless the riders have done their homework, justice will be served. Someday you may pass one of them on the side of the road with a seized engine. However, on behalf of those of us riders who pay attention to things like that, sorry we'll try to keep it down!