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Issue link: https://magazine.cyclenews.com/i/126394
The bore job plus a jusicious increase
in main jet size from 125 to 140 burnped peak power up above 50 hp, a full
11 % above stock ,
The handling problem was felt to be
the result of inadequate rear damping,
so the S&W 's were replaced with a set
of Boges with their hardest damping
rod . The solution to the gearing problem was available but required split ting the . engine cases to install the
taller 1977 gearing, Since the bike was
winning anyway , we decided to forego
that chore,
The next race was Charlotte (North
Carolina) Motor Speedway on July 1
for a 500 km enduro plus sprints. And
though we won the endurance and 750
Production races, the handling had
now deteriorated to the point that
racing was losing its attraction. I kept
noticing spectators running for cover
as I came hopping through the infield.
The power and ground clea rance
problems were solve d. but th e niceties
were beginning to seem very irnportant oBack to the shop.
The bike's behavior at Cha rlot te
m ade us feel that the p roblem was a
front suspension that was over sprung
and under damped. To correct this we
switched from the XS 11 touring
springs to standard XS I I springs and
changed the fork oil from 20 wt. to SO.
Another race at Charlotte showed some
improvement. but not enough. The
bike required very smooth modulation
of throttle and brakes to avoid pogo·
ing, nor would it countenance a sudden change in line in the middle of a
tum. By now the season was near an
end and the bike still would not handIe. As a last resort we decided to try a
set of IS" Kayaba gas shocks with 115 /
185 springs which had worked on
another XS750 racing effort.
Finally at Atlanta International
Raceway, seven months after the
project began. the bike handled. With
an honest top speed of 120 m ph, good
handling, good brakes, and great
ground clearance. the bike took firsts
in 750 and O pen Production, and had
a lot of 750 Production racers muttering about protests. .The underdog
had become overdog,
T he final race of the year was to be
the WERA Grand National at Texas
World Speedway, This was a race we
very much wanted to win , so we bit the
bullet, split the cases. and changed the
overall gearing to that of the higher ,
2D model. While we were at it, we
freshened up the valves and were
rewarded with a dyno run producing
the highest torque figure we had seen
all year, Feeling like the bike was
developed as far as we could take it , we
set out for Texas. hoping to finish the
year as the top 750 in the country,
In Texas the bike ran , handled, and
stopped as well as could ever be ex pected from a production legal motorcycle, pulling an honest 126 mph with
the new gearing. Unfortunately, the
rider wasn 't as good as the bike and we
ended up about ten feet short, the difference between first and third in the
750 Production race ,
So that was it . After 22 dynarnometer runs, three major engine teardowns, three sets of shocks, three sets
of fork springs, seven valves. three
pis tons. one universal joint, eight
Michelin PZ-2 's. 28 quarts of oil, 3bOO
travel miles, and u ncount a ble hours of
labor , this is what we had: 6 firsts, 4
seconds, 2 thirds, 1 fourth, no
DNF s. no crashes, and the feeling that
everyone who saw it race would agree
that the Yamaha XS75 0E was as goo d
a ro ad racer as any motorcycle in its
class . And though a lot of folks won 't
seem to believe us, ours is still a nice
touring bike, stock as a stove.
•
Announcing a .Revolution.
The Mateo MBgnum Enduros.
This is the year it happened, Maico is bringing Magnum performance
to Enduro competition , " and they' re serious about it, Never beforein a single model year - have inventive Maico engineers brought
so much to the sport.
a-
IlIore H.P.
1J»s. The Power Is up in a new Magnum eng ine with special alloy ,
pistons. CiP lightweight crankshaft. and '79 porting. The famous Malco powerband Is
there, but OYerall weight Is down.
A RadIa1 " _ PnttIIe A s haped swIngarm lowers the center of gravity, lowers
the seat height. The countershaft sprocket moves next to the swIngarm pivot
,
eliminating twelve cha in links and tensloners .
EDdaro nep.nd-hlUty An even ten Inches of travel front and rea r with air forks
and dual rate spring mounted g85 s hocks. Bosc h COl ignition. Qu iet double-w
all
exhaust pipe with Skyway s park arrestor. Metzeler tires on rugged gold
anodized rims.
'
Endaro PesfonDallce A new unlned command unit including speedometer, hom,
front number plate and headlight. CiP side number plate. rugged rea r fender and taD
light. long·range g85 tank. center s tand. chain guard and much mo re •.• it's all
s tandard. all race-ready at your Malco dealer. If you're ready to move up in class, get
on a Magnum Enduro - 250, 400 or 4 50 ee,
MN::n
1~ Plogoes
Rd..
s..-. VA 2J434. Rt. I. Boa 21 1. _
Clubs· Promoters· Dealers
Go'" the Traile Expos?
. IL60002' 110 E.
s.u Ana Ave.• !lurt>onIl. CA 91502· Canedo -
64 H