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Motorcycle engines use
the power generated by combustion for a number of purposes. Three
key areas of power usage are:
- Turning the rear wheel
- Drawing air into the engine
- Forcing exhaust gases out
To get the most performance out of a motorcycle engine, it is
important to focus as much of the engine’s output on turning
the wheel as possible. One popular modification to help in this
pursuit is replacing the restrictive stock exhaust with a free
flowing aftermarket exhaust. Some people think that the main objective
in picking an exhaust is to find one that sounds the best. Realistically,
if you pick an exhaust that matches up well with the performance
level of your motorcycle the killer sound will almost always take
care of itself. When selecting an exhaust, there are two main
categories to consider, full system and slip on. Both increase
the motorcycle’s power by reducing the amount of resistance
in the exhaust system, allowing the engine to devote more power
to moving your bike and less energy on expelling exhaust gas.
  
 
Stock Exhaust on a Kawasaki KLR650
Full system exhausts connect directly
to the engine’s head, replacing the OEM muffler and pipes.
This style of exhaust requires a more involved installation process
but results in increased high-end power. High-end power is important
when the motorcycle is often used at full throttle, for example,
long trips at highway speeds. This exhaust will have the greatest
effect on increasing the motorcycle’s maximum speed.
Slip-on exhaust systems are easy
to install since the headers and pipes closest to the engine remain
in place. Slip-on exhausts increase a motorcycle’s low rpm
power. This gives the bike more pick-up for quick acceleration.
For most riders, it is more practical to increase the motorcycle’s
low-end power, as it is more useful in daily driving. Many riders
never see their motorcycle top speed and are not particularly
concerned with increasing it. If you are more concerned with the
ability to take off from stoplights, a slip-on exhaust might be
right for you.
Installing either type of motorcycle
exhaust is relatively easy since the pipes simply bolt together
and most bikes offer decent access to the bolts. When installing
an aftermarket exhaust, it is always a good idea to install new
gaskets. They are cheap and easy to throw in place and making
sure the exhaust seals well will prevent problems down the line.
Since the new motorcycle exhaust is changing the airflow through
the engine, it is a good idea to install a new air filter and
adjust the carburetor. This will help maintain the best air-fuel
mixture for the best motorcycle performance.
Most quality aftermarket motorcycle
exhausts come with removable baffles. You can add or remove baffles
to tune the level of backpressure in the motorcycle’s exhaust
system. Too little backpressure can allow raw gas and fresh air
to be expelled prematurely, reducing the amount of air and fuel
in the combustion chamber. Too much backpressure can rob your
engine of horsepower since it has to work harder to expel the
exhaust (it also affects the engine’s ability to draw in
fresh air). By adding or removing motorcycle exhaust baffles;
you can tune the bike to peak performance.
Baffles from a SuperTrapp Slip-on Exhaust
Some motorcycle exhausts have mufflers are packed with sound deadening
material, usually a fiberglass. Overtime this material will wear
out and the exhaust will have to be repacked to keep it sounding
right and tuned properly.
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