1976 Yamaha XS500 -- 2-Page Vintage Motorcycle Ad

Description

1976 Yamaha XS500 -- 2-Page Vintage Motorcycle Ad
Original, vintage magazine advertisement
Page Size: Approx. 8" x 11" (21 cm x 28 cm) each page
Condition: Good
The sophisticated four- stroke Yamaha XS500:
A touring machine with roadracer handling.
An eight-valve,
dual overhead cam twin is
not the typical production
engine. It’s more like a racer’s engine.
This engine explains why the Yamaha
XS500 is like no other motorcycle.
It explains why the XS500 is indeed
a touring machine with roadracer
handling.
First, the engine’s design. It’s an
example of an engineering concept
well known in racing: maximum
horsepower developed without
increasing displacement.
In essence, the XS500’s engine
does its job more efficiently. The
valves are an example of this. A con-
ventional four-stroke twin has four
valves. The eight-valve design pro-
vides greater valve area and in-
creased breathing capability. Each
phase of the four-stroke cycle is
accomplished more efficiently: The
combustion chamber is more com-
pletely filled with fresh fuel during
the intake stroke and burned gases
are scavenged more efficiently
during the exhaust stroke. That’s
why the XS500 is more powerful
than any conventional four-stroke
twin, without being larger.
The XS500’s engine also has a
higher rpm capability than a con-
ventional four-stroke
twin. A com-
parison of the
valves reveals this
(see illustration). 30 mm
is the diameter of a typical
four-stroke valve. 24 mm is the
diameter of the XS500’s valves.
That’s an important advantage. A
larger valve weighs more, and floats
more readily at high rpm. A smaller
valve, like the XS500’s, doesn’t have
this problem. That’s why the XS500
can redline at 9,000. There’s
more useable power.
The combustion chambers (as the
engine cut-away shows) are more
hemispherical in shape than those
of a conventional four-stroke. And,
as engineers will tell you, the hemi-
spherical combustion chamber is the
ideal shape. The twin 38mm Mikuni
XS 500 valve
Conventional
500cc twin
valve
Less mass means
less power drop-off
at high rpm
the power for
this engine with good fuel economy.
And because the XS 500 s
engine is small yet powerful, it can
be fitted on a frame that’s a direct
descendant of the world-famous
Yamaha 350 roadracer. And that’s
why the XS500 handles so well.
It’s a motorcycle whose perform-
ance is perfectly suited to back roads
or freeways. It’s nimble yet powerful.
And the details of its construction
insure reliable operation. The
cylinder head and cam case are cast
as a unit to reduce oil seepage. A
new positive crankcase ventilation
system stops oil mist vapor from
leaving the engine.
The 1976 Yamaha XS500. It’s
the most sophisticated motorcycle in
production, and an example of what a
four-
stroke twin should be.
12165-7603-04