Dirt ad Trail Online Nov 2020

Parralel twin.
of fuel being compressed, burned and
exhausted. However, where the normal
engine must convert the power generated
forcing the piston down the cylinder into
a circular motion through the crankshaft,
the rotary engine has a rotor spinning
inside a chamber performing the same
function.
As the rotor spins in one direction
only, and does not have to stop at the
beginning and end of each cycle (four
times per power cycle in a 4 stroke, and
twice in a two stroke), it is continuously
sucking in fuel, compressing and burning
it as well as expelling the exhaust.
The power shaft is being driven
continuously. This makes for a very
smooth and powerful engine. It produces
more than double the power of either a
two or four-stroke engine and has similar
characteristics to a jet turbine engine.
High power but woefully inefficient and
very heavy on fuel, and it also produces
an unacceptable amount of toxic
emissions. It is also very complex and
expensive to manufacture and maintain.
Having said all of this it might still make
a comeback as technology progresses
because it has the advantage of small
size, and it can run on almost any type of
combustible fuel.
Suzuki and DKW both bought licenses
from Wankel in the mid 70’s, and whilst
DKW brought out a lightweight rotary
engine dirt bike, Suzuki produced the
incredibly heavy and complex RE5. Nice
bikes to ride, but thirsty and unwieldy,
they were overshadowed by the excellent
GS 750 and soon both the DKW and the
RE5 faded away into history.
Norton, in its first re-incarnation in
the UK developed quite a successful
800cc rotary, which they again raced
very successfully and ended up with a
reasonably successful production rotary,
which included a very reliable police
version.
Diesel:
Because of their power characteristics
and bulky size and weight, Diesel
engines are not a huge line for
motorcycle manufacturers. Bikes are
mostly about excitement – and small,
normally aspirated Diesels provide more
torque than top-end, thus, manufacturers
tend to fit them into workhorses like Side
By Sides and some of the Utility ATV’s.
The basic difference between a diesel
engine and a petrol engine is that in a
diesel engine there are NO spark plugs.
The fuel is sprayed into the combustion
chambers through fuel injector nozzles
just when the air in each chamber has
been placed under such great pressure
that it’s hot enough to ignite the fuel
spontaneously. A diesel does not run
with traditional spark plugs because they
do not need fire to burn - combustion
happens under pressure.
They do, however, have glow plugs to
heat the fuel for starting purposes. Diesel
powered Bikes include the likes of Royal
Enfields bullet that sells reasonably well
the world over, but the big market for
SA are machines like the Polaris Diesel
UTV’s, Kawasaki’s Mule UTV’s, both
aimed at the mining and agricultural
markets.
The U.S. military also developed and
successfully ran a fleet of Kawasaki KLR
650’s that ran on diesel and paraffin …
and basically any crude fuel they could
find out on the battlefields of the world.
Engine configurations:
Whenever you read a bike test – you’ll
see that we often refer to what kind of
engine powers the machine – ie – parallel
twin, Vee twin, single cylinder and so-on.
Some people confess that they often
have no idea what we are talking about.
There are plenty of non-technical people
out there, so maybe, this will help. Please
bear in mind that we are not boffins -
VFR1200F V4 engine
we rely on our wives to tell us
everything... But here’s what we do
know…
Here are some of the engine
configurations on the market at the
moment, or which have been produced in
the recent past. Different configurations
make power in different ways -
IE: and inline four is generally smooth
and is fairly predictable – while a
V-Twin… well - ride one. You’ll get the
gist of it.
Single cylinder: 1 piston that moves up
and down.
The piston and barrel can basically fave
in any direction or be slightly inclined.
Four stroke or two stroke.
The vast majority of dirt bikes have these
engines fitted, in various sizes. Most
manufacturers offer a single of capacities
from 50 cc up to around 700 cc.
Water cooling, fuel-injection, electronics
and balance shafts make them
sophisticated and reliable.