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Bonneville Report 2007
I post this per Matt's request:
Two months ago we were contacted by Triumph USA to build a Thruxton to
take
to the Bonneville salt flats for the 50th anniversary of the Triumph
record
runs, after which the Triumph Bonneville motorcycle is named. The bike
built
for the Triumph UK team is unfaired and a similar bike built for the
French
team sponsered by Hein Gerike has a custom fairing. The two bikes have
similar engines (over 100 hp at the rear wheel). They run in different
clases due to the fairing on the French bike.
The Bonneville salt flats greeted us with rain, wind, and an absolutely
awesome display of lightning strikes. My initial impression was not too
good, based on my previous trips here in '88, '89, and '93. The salt
was wet
and soft and would not have time to dry out and reharden during the 3
day
meet.
Our primary purpose this year was photos for the upcoming advertising
campaign. Although I realized that the record of 154mph was probably
not
attainable even in perfect weather, I still hoped the bikes would show
well.
The French bike with the custom fairing, ridden by Alain Miran, ran as
high
as 149.8 mph during the meet. The first run of the UK Thruxton, ridden
by
Alan Cathcart, was a very respectable 140+mph. We did some minor tuning
(jets, etc) and with some further instructions to our rider, the bike
ran
over 146mph.
We installed a rain tire (better tread for the slushy conditions) and
changed the gearing, and with only 30 minutes left, Alan qualified
(within
5% of the existing record) on the 1 mile course, allowing us to
continue. We
went to impound for a fuel check, and with only 15 minutes remaining,
we
rushed to do a few last minute tweaks (raised the air pressure to 50lbs
and
added an ignition booster). I had a theory (after studying 7 different
runs), that the 12 to 1 CR pistons might be blowing out the spark, and
I
just happened to have an ignition booster in the spares vehicle. The
updated
instructions to Alan were to be sure to rev the engine all the way to
9500
rpm before shifting into 5th gear (which would allow the bike to pull
properly in 5th without bogging down). It worked perfectly - as the
bike
disappeared into the white horizon, I could hear it rev and rev. At the
tower, I was presented with a time slip showing 148.245mph (not quite a
record, but considering a 15mph headwind and slushy conditions, an
excellent
run overall, especially on the one mile course).
Looking back, I was surprised to do this well. Realistically, I had
hoped to
reach 140. Missing the record by only 6mph under less than great
conditions
and with a conservative engine was an unqualified success. The engine
ran
over 31 miles total at over 9000 rpm with no leaks, no glitches, no
problems
at all. The engines were increased to 988cc, have 12 to 1 compression
ration, streetable cams, and with some fine tuning during many dyno
runs,
achieved 101hp at the rear wheel.
Oh yeah, we did win our class (1000cc unfaired)! As a final farewell, I
ran
the Mirage bike just for the fun of it and hit 145 with the wrong tires
and
wrong gearing. All the bikes ran and handled flawlessly with no
problems at
all. We all had a great time and are already looking forward to next
year.
Matt Capri
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