Engine Block
The liquid-cooled, 499cc V-four
motor produces around 190 hp at
13,000 rpm, but to make that kind of
engine takes big money and hundreds of man-hours of development.
The motor features crankcase reed
valve induction with a powervalve
exhaust system. The longest single
production process is making the
magnesium crankcases. Yamaha has
to get these from a specialist foundry
and the casting takes two months to
produce. To then build a complete
engine from start to finish takes three
months. That doesn't take into
account the design stage, since the
current engine concept is not new,
but a refinement of a long-term existing design. Crust revealed: "If we
were building a new engine, it would
take at least half a year. For example, our type of cylinder is one we
have been using for some time, but if
we try a new concept, the design
takes two months and then casting,
machining and coating will take
another month. We then spend two
months bench-testing, which includes
performance-testing, seize-testing
and wear-testing, to make sure all the
components are reliable."
Cylinder/
Cylinder Head
The YZR has five different cylinder
Gcrankcases
shapes available, each one designed
to give Biaggi more usable power at
Aluminum may last longer, but
Yamaha chooses magnesium for the
crankcases because the metal adds
to the stiffness of the chassis when
the cases are bolted into the frame.
The cases last 2000-3000 miles and
are then replaced, because that is
Yamaha's recommended lifespan for
the component. Crankshafts last
around 625 miles.
eye
I
e
different circuits. It's not just port
design that varies; there are also different exhaust valves to suit various
tracks. When Biaggi was racing in
South Africa earlier this year, he used
a different head volume to cope with
the lack of air pressure at high altitude. The cylinder head has a sensor
built into it so temperature and presn
e
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AUGUST 15, 2001
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