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(Above) The new Honda works bikes retired with frame cracks. (Below)
This FZ750 uses a TZ250 front end with Brembo brakes.
Endurance
technolog~
,
LeMans
from
By Peter Clifford
There was li ttle doub t a bout w h ich were the
m ost impressi ve-looking machines at th e
L eMans 24 hou r race; the n ew works Hondas
freshly p ainted in their Rothmans colors. T he
team had all the trappings of
big time endura nce raci ng complete with the $150,000 coach
also used by the Roth rna ns G P
team.
The beautifu l Hondas looked as
though th ey might hav e been th e
same ro ll ing cha ssis as Freddie Spencer 's So u th Afri can Grand Prix winning 250 wi th a V-Io ur 750 engine.
They use the same twin spar frame
arrangement that Honda has now
made common to the 250. 500 and
750cc works ra cers. As well as in
endurance races. similar 750cc V-fours
will also be used for the World Championship TT Formula One races.
It would seem likel y that th is will
herald a range of street bike fram es
with a similar config ura tio n but presumabl y first they will dream up
some cute phrase in the same vein as
Pro-Link, TRAC orATAC. T he rea so ns for ado p ting thi s method o f
fram e producti on are severa l and th e
V en g ine co n fig u ra tio n p robabl y
pointed fram e design in this direction.
Once they had decided to run twin
spars on either side of th e en gine the
obvious thing was tolink the steering
head and the swi ngarm pivot as di rectl y as pos sibl e.
The endurance racer, in common
with the otherHondas , has twin rectangular section tu bes running down
to a mach ined section which curves
around the back of the gea rbox . Beca use the 750cc four-stroke is wid er
than th e 250cc o r 500cc two- strokes,
th e twin spars must a lso be wider.
This ha s necessitat ed skim ming the
corner or th e top of th e side rails to
allow the rider to tu ck h is legs in
against th e tank.
Un fortuna tely Honda 's endurance
Yoshimura-tuned GSXR750 Suzukis finished first and second; note extra
oil tank over countershaft sprocket. (Below) 1050cc Kawasaki Ninja.
effort a lmost met with disaster when
both bikes had to be retired at LeMans
beca use of termin al fram e cracks that
threat ened to separate the fro nt forks
fro m the rest of the machi ne.
When Pierre Bolle called in for a
routine pit stop a t 2:00 a.m. after
nearly 12 hours of raci ng , he pointed
out to his mecha nics that the han dling had gone off slightly. Those
watching th e pit stop could see the
frantic activity that started when o ne
mechanic very quickly noticed the
cause of the problem. The 6-inch
deep main spars had large cracks
running up each of them behind the
steering head. It looked as though
o n ly som e 1.2-inch es of uncracked
material remained. The other works
Honda was ca lled into th e pit, and as
similar cra cks had started on it, both
bikes were retired.
An unfortunate end to the bike's
first endurance race, but Wayne Gardner had already won a sprint race on
one of the F·I machines at Japan's
Suzuka circuit before the start of the
G P season, and it is just as well that
the problem occurred at LeMans a nd
was spotted ra ther than at a road circu it like the Ulster or the TT where
the bumpy circuit is so much harder
on th e machine and the result co u ld
have been tragic.
It is not easy to point to the cause of
the fa ilu re as the section of ma ter ial is
so co nsidera ble at that point, bu t the
met hod of engine mounting ma y be
suspected. The four stro kes are sus pended from the forward cylinder
heads by very stiff-looking mounts
an d would transmit a good deal of
head vibration straight to the frame
close to the point where they broke.
Strange though , that such a failure
did not show up in Honda's own testing as they would probably have p ut
pro totypes through more th an one
24-hour-race worth of mi leage. Cu ring the problem mig h t not be as easy
as beefing the frame up in that area as
vib ration of an even stiffer section
might p rove just as destructive. Rubber mounting might be the answer
but could upset the resi of the desi gn.
T he detail work on the Ho ndas, as
a lways, is superb, with some new
four-piston front brake calipers from
Nissin. As usual the pisto ns are different sizes to stop the leading edges
from wearing more than the trailing.
Pad removal is neat; a single pin
holds both pads but this is weIl
secured. A spring-loaded arm ho lds it
in place and must be depressed by one
finger as the pin is pulled out.
Interestingly, one of the main problem s that the Hondas had during
practice involved the choice of whee l
diameters as they cha nged from 17 to
IS-inch wheels and back for both
front a nd rear. ,It looked as though
the bike was designed to run a 16inch fro nt as bo th the 17 and IS-inc h
tires touched the fairi ngs, wh ich had
to be cut away. H o nda continues to
ru n Micheli n tires a nd that in cluded
a new IS·inch rea r wit h a varie ty o f
constructions being used a ll aro und,
in cl uding radial s.
As on Spe ncer's 500 an d 250, the a ir
intake fo r the carbs is u nder the steering head a nd the flow is ducted over
the forward pair of cyli nders, T he
magnesium-bodied CV carbs are no t
contained in a full ai rbox, tho ugh.
Ra n ged against these impressive(Con tinued to page 20.)
