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The bad news is, the 1981 YZ's are even
more awesome than the ones you couldn't
catch last yem:
The good news is, you can buy one.
And reverse the trend.
This yem; we made every one ofour big
machines more powetful than ever before.
Not just the wide-open, flat~ut variety, but
a steady stream of useable power through
out the rpm range.
No simple task, especially when you
considerthat we had to literally re-engineer
each engine according to its size and
petfonnance characteristics.
There was no one formula But a
unique combination of ingredients to make
them go fast; fast, fast
Go with the flow. Perhaps the most
dramatic example of Yamaha
ingenuity solving a specific perform·
ance fmJblem is ourrevolutimulry
new Yamaha Energy Induction SysI, tem (YElS for short) on the fZ25O.
It /1tdS a" end tf) the low and
mid-range power drop caused by the
uneven, pulsing flow ofthe
air!fuel mixture, and the
resulting 1Ieed to compromise carburetor jetting.
~
YElS btu 110 moving
~ parts. Just a small chamber
linked by a hose to the imake
manifold. A vacuum created
i" the chamber by crankcase
VlJCUum on the intake stroke maintains a smooth air/fuel f/ow until
(he next intake stroke. With engj1le
vacuum and chamber vacuum alternateJ.y puUing this steady f/ow
throllgll the carburetor, .l"U can set
~ jetting for maximum power
arul efficiency.
Andsetyour sights on win"ing.
10
GnpWe ........ 17Ie rrsrdts ofall DIU /IOft1er.btJostj. ~ e{fiJrts
ani re/ItIt:t«l. tile ~ atnJeS 011 tItis gN/JII-l!J8O .. 1!J8L LooIts
like J!J8J. is gohtg to N (l vny good yem:
~
~--
:.......:.-----JlHi-------,l~----
Good timiDg. A miUimeteror two
mport timitlg-
both size arul
pU.u:ement -can restIlt i" a real
pe.foI- i_tue.
For 1981, we've sigxi/iullftly
imtmnJed both the irUtzke arul
ezluJust port timing 011 eodl ofour
big yzs. And 011 the 125 specifiadly,
