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Motorcycle
Transmissions and Exhausts
Transmissions
Manual transmission. Most bike transmissions are manual
sequential gearboxes, with neutral positioned between first
and second. After second gear each gear can only be used in
order. Reverse is only fitted to the largest touring bikes
like the Honda GoldWing.
Automatic transmissions can be found in many scooters
and some touring bikes.
Chain drive is the most common form of transmission
to get power from the gearbox to the rear wheel. Chains require
regular maintenance and lubrication. They also require periodical
adjustment and change because of the stretching incurred over
time.
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Shaft
drive is found on many touring bikes and BMW uses them
on many of their models. Shaft drive units are completely
enclosed and almost maintenance free, quiet and clean. Shaft
drives drain power from the engine because of the complicated
gearing required, they are also heavier than chains or belts.
Belt drive is found on many Buell bikes among others.
Belts are quiet, clean and efficient although they do stretch
over time like a chain. Belts are limited in the amount of
power they can handle.
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Exhausts
The position of a motorcycle's exhaust can effect the bikes
characteristics, especially on high speed sportsbikes.
Underseat exhausts, a Ducati favorite since the famous
916,
were developed to reduce windresistance by putting them up
out of the airflow - good. As a by product it raises the bikes
center of gravity - not good.
The traditional position of exhausts, either side of
the rear wheel has its advantages and disadvantages too. First
of all they are not the best looking pieces of kit and can
clutter up the appearance, they can also disrupt airflow and
ground clearance can be in issue. But if they are positioned
low they can help lower the center of gravity, they free up
underseat space for storage and the engineering is thoroughly
researched.
Aftermarket performance exhausts can expel exhaust
fumes faster permitting a longer power stroke. However, many
modern production bikes already have a tuned system and an
expensive performance exhaust may only operate effectively
at a narrower rpm range. Louder, and often illegal, some belive
that performance exhausts are safer as they can warn people
who may have failed to see the bike.
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