The engine improvements
include the adoption of a YZR250 type cylinder
body, and new carburetor settings, etc.,
that provide better power feeling across
the full rpm range and improved acceleration
performance. The chassis adopts a YZR250
type cowling, seat and front fender for
improved aerodynamics and top-speed performance,
making for more stable handling performance
at high speeds.
While maintaining the outstanding characteristics
of the sand cast type crankcase, liquid-cooled
2-stroke, 90°V-twin engine of the existing
model, engine improvements have been made
that include the adoption of a YZR250 type
cylinder body (special type YPVS valve incorporates
exhaust branch function), new exhaust timing
and a new shape for the initial scavenging
section of the crankcase. The combined effect
of these improvements boosts performance
across the entire rpm range. (The existing
model features a slide-type YPVS valve).
In particular, the new cylinder and drum-type
YPVS valve boost performance in the low-
to mid-speed range and contribute to reduced
exhaust noise. The new exhaust timing improves
performance in the high-speed range, while
the new initial scavenging section shape
contributes to better torque characteristics.
The piston features a
new shape in the upper portion of the pin
boss for optimized strength balance plus
a WPC finish on its outer surface for greater
durability and reduced friction. Durability
has also been increased by changing the
shape of the crankcase journal section.
(WPC treatment is a type of treatment for
increasing the strength of the surface layer
of a metal that involves high-speed peening
of the metal with a shot of just a few microns.
The high-speed peening heats up the surface
to the point where it melts once. Then it
is rapidly cooled to produce stronger crystallization
of the metal.)
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