Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/125853
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Pelroehem CABLE
LIFE MINUS 70 '
is formulated
specifically for
snowmobiles and
m oto rcycles. St ay s
fl uid t o 70 de grees
below zero. Aid s
i n preventlnc
throttle CJIble from
freezi nc In the
open position.
Dis p laces m o isture,
lu b ricates and
rustpro ofs all
moving part s.
Dr. Schnurle made the two-stroke competitive in 1935 with loopscavenged spli t -singles. This 1939 model features water cooling.
bit in th e way of reliab ility and hand ling
to stay with t he Moto Guzz i singles.
Th ese Deck s had the first ind ications of
an expansion cha mber ex ha ust sys te m,
b ut they wer e developed m o re through
tria l and error than any scien tific
calc ulatio n .
Walter Kaaden was t he man who
really got th e tuned exh au st theory fo r
tw o-strokes o n th e road to success when
he design ed th e first true expansion
chambers th at helped th e 125 and
25 0c c MZs to man y GP wins. Kaaden
found th at he co uld ta ke ad vantage o f
th e sound and pressure waves inherent
in th e exha us t sys te m to increase th c
power outpu t o ver a narrow RPM range .
The idea w as to use th e pressure
d epres sion, o r va cu u m , in th e e xhaus t
sys tem to help pull t he incom ing fuel
charge from th e transfer ports into th e
cy linde r. He di scovered th at he co uld
also u se a n ega ti ve pressure wave t o
push the esca p ing fu el charge back into
th e cy lin de r late in the intake cy cle.
T his worked o nly over a n arrow rev
ran ge in his ro ad racers, but th e power
o ut pu t took a great j ump. Subsequent
resear ch revealed th at a properl y
de sign ed exhaust sys te m co uld be tuned
for ju st ab o ut an y rev rang e or type of
perform an c e desired ; for trials,
motocross, o r roadster use.
This significant invention put the
two-st roke in the winner's circle once
again, and e xpansion chamber exhausts
soon be gan' to app ear on motocr oss bikes
and even tnals models. Roadste r
application ca me last , but today all
two -stro kes have a very carefully
design ed e xhau st sy stem th at provides
per form an ce to match the intended use
\
o f th e bike.
Walter Kaaden then perfected the
idea of a thi rd transfer port in the skir t
o f th e pis ton, wh ich was or iginal ly
th ought of as a m ean s to ge t e xtra
lubricati on to th e wr ist pin bearing:
Another po we r increas e resulted, but
the tiny MZ co nc ern lacked th e fin an ces
to fully develop their ideas in
co mpetit io n o n race co urses to ga in the"
World Championship they de served,
b ased on th eir e ngineering a d vances.
T he se
t w o in ventions , l oop
scavengi ng and th e e xpa n sion chambe r,
are sti ll the most signific an t innovations
in 't he en tire hi story of th e two-stroke .
With them we ha ve a winner, and
without the m w e would still have no isy,
low power, unreliab le en gines fo r utility
vehicl es.
. •
Walk
before you
run Mickey QuadeTibblin
Then let Rolf
and
.-
)
l-o
0..