The '03 Big Dog
Mastiff with a 107ci S&S and a stock G
carb, the stock Mastiff put out 94.1 hp
and 102.6 lb-ft of torque. With the air
cleaner assembly and backing plate
removed, DaVinci drained the fuel in the
bowl, removed the float bowl screws, and
then the bowl itself.
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Next, the main
discharge tube was pulled out of the
carb body assembly, so he could install
the DaVinci kit.
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Here is the entire
DaVinci kit: a special booster anchor
socket wrench, Loctite, annular
discharge booster, booster anchor,
discharge tube, and main jet.
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To install the
kit, we simply placed the booster anchor
into the supplied socket wrench with a
little Loctite on the threads and placed
the booster inside the venturi of the
carb. Then, we put the anchor and socket
into the main discharge tube hole and
tightened it down snugly. We then,
screwed the new discharge tube into the
main discharge tube hole along with the
included jet, just as we would with a
normal S&S G carb.
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Don't forget to
put on the float bowl gasket, then screw
the float bowl back into place.
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7Using a hex key,
DaVinci bolted the backing plate into
the head and put the air cleaner and
cover back on in preparation for our
second dyno run. All DaVinci did was
bolt on the DaVinci kit and the bike
produced 99.6 hp and 107.8 lb-ft of
torque -- a 5.5hp and 5.2lb-ft of torque
gain in 15 minutes!
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The DaVinci Fire
Power Carburetor is a true performance
upgrade from the original S&S G. You can
see some of the differences between the
S&S ...
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.... and the
DaVinci Fire Power. Tthe Fire Power carb
comes chrome-plated, the annular power
booster is factory installed, it has a
replaceable high-speed air-bleed to
allow tuners to customize their fuel
curve, extended hexagon bowl bolt screws
to improve access and reduce time when
removing the bowl while it is still on
the bike, an extended idle screw knob
that allows adjustments to be made by
hand, and the main fuel jet can be
changed using a standard jet tool
without removing the bowl.
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The inner diameter
of the venturi on the Fire Power carb
has been precision machined and bored
from the original 44mm to 48mm, then
hand blended to final size, shape, and
finish.
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To further
increase airflow, the butterfly shaft is
milled from 0.280 inches to 0.170
inches. This increases the air flow to
385 cfm -- a 36cfm increase or about a
10-percent total gain over the stock S&S
G.
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Installation of
the Fire Power carb is just as easy as
installing a stock S&S G. We detached
the fuel line, unbolted the carb from
the manifold from the primary side of
the bike, and removed the throttle cable
ferrules from the throttle spool.
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We grabbed the new
Fire Power carb and inserted the
ferrules into the Fire Power throttle
spool. Then, we put the phenolic spacer
back between the carb and manifold, and
bolted the carb to the manifold.
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Then, we hooked
the fuel line back onto the fuel inlet
on the bottom of the bowl and tightened
the worm screw on the hose clamp. The
backing plate went on next, followed by
the air cleaner and the cover.
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Nigel Patrick of
Patrick Racing performed his final run
of the day with the Fire Power carb
installed. The bike still looks stock,
but the numbers don't lie.
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Our final numbers
of the morning were 106 hp and 107.1
lb-ft of torque -- the Fire Power carb
produced 6.4 more hp than the DaVinci
Kit and a total of 11.9 hp and 4.5 lb-ft
of torque more than the stock S&S G!
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| SOURCES |
Street Chopper Magazine
www.streetchopperweb.com |
Patrick Racing
(714) 554-7223
www.patrickracingbillet.com |
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