The Flapper Mod.
This is by far one of the best mods I have done to the cbr1000rr.
One because it’s free and two because it takes all of 10 minutes to do and three
you can reverse it in 10 minutes also. Although I don’t know why anybody would want to.
What is this flapper valve? and what is it for?
The flapper valve is a Ram air restrictor plate that Honda has installed on this bike to limit the
use of the ram air system.
Honda's marketing machine tell us that the intake flapper valve is there to increase low rpm intake velocity which
in turn improves throttle response. This sounds very convincing, but inside sources from Honda have leaked the
real reason; To pass noise emission requirements.
Photos By Mad Mardigen
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Here is how it works.
The ram air restrictor valve is open by default. Although as soon as you put
the bike in gear and start to ride, the valve closes forcing the bike to breathe through two smaller openings on each
side of the ram air duct. The valve stays closed until the engine exceeds 5000rpm
(The noise emissions’ tests are performed from idle to 5000 rpm) at this point the valve opens up and
stays open as long as the bike is in gear and the engine is above 5000rpm.
So what is the Flapper Mod?
Very simple, disabling the flapper system. The ram air flapper valve is open by default so we will just stop
it from closing.
What are the benefits?
You gain a couple of horses and a few ft/lbs of torque below 5000 rpm. I can’t confirm this, although others have dyno'ed their bikes with this mod
and this is what they reported. What I did notice is the bike rides a whole lot better; smoother. Up shifting and down shifting is like butter compared
to the notchy feeling before. Oh! and on top of that, the engine produces a nice induction howl.
Photos By Mad Mardigen
With your hand reach in to the left mid fairing
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Photos By Mad Mardigen
Pull the rubber hose off the vacuum diaphragm and pull the end of the hose out.
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MAINT.
DIAGRAM
