Air box flapper doesn't close. - Wrist Twisters
 
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post #1 of 8 Old 04-03-2013, 10:29 PM Thread Starter
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Air box flapper doesn't close.

I read about the air box flapper, it said it kicks in at a specific RPM. I looked to see and mine was still hooked up, I jumped the bike, revved it up and it never closed.

I checked the hose and it doesn't seem to have any vacuum. When is the flapper supposed to be closed?

I didn't check to see if the hose was connected way up under the tank, but I'll get to that someday.

Where does the hose get it's vacuum from, intake runner or air filter box?

I know it doesn't need to be closed, and there's a popular mod to keep it open, I'm just wondering why it doesn't work. Might indicate a problem, even a vacuum leak if it fell off.

My guess is that it's based on vacuum from an intake runner and under high vacuum it'll close?

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post #2 of 8 Old 04-03-2013, 10:39 PM
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It closes on hard deceleration after high RPM's, so basically after an extended high speed run and immediate close of the throttle.

Not sure if it only does this under load, though?

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post #3 of 8 Old 04-03-2013, 11:57 PM
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Vacuum for the flapper is supplied by cylinders 2 and 3 off a 4 way t that also supplies vacuum to the for. The flappers operation is controlled by a vacuum cylinoid from the ecu. The specifics of its states are debated but its common for the flapper to be closed at lower rpms to reduce intake noise to pass emissions certifications.

Do yourself a favor and grab a small vacuum cap n cap the line off at that 4 way t, then remove the hose , cylinoid , storage canister and vacuum operated switch in the intake.... Its all useless and just ads extra weight and reduces power at lower rpms

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post #4 of 8 Old 04-04-2013, 12:10 AM Thread Starter
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ok, so it might be working fine, can't tell just by revving the bike.

I'll have to take that out soon.

I was kinda surprised with the noise. I read that the 919 intake was really loud, it's not that loud at all. I saw an 'intake mod' somewhere, but when I took off the cover and filter, it wasn't that much louder.

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post #5 of 8 Old 04-04-2013, 12:24 AM
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Just disable or remove it. It makes a difference in hard acceleration between 5-6K rpms.
You might get feedback from some guys that it doesn't make a difference, but it does. The guys that don't notice the difference either don't ride that hard, or are just a little more unaware of what their bike is doing.

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post #6 of 8 Old 04-04-2013, 08:05 AM
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Anyone dynoed the bike before and after the flapper removal?

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post #7 of 8 Old 04-04-2013, 08:23 AM
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here's an explanation of what it does and some background info on the flapper mod, from a credible source:
ROGUE RACING CBR1000RR Intake Flapper Valve page
Quote:
we have tested it (as have many others) on the RC51 & the 919 & on both bikes the mid-range horsepower was increased slightly (usually 1-2 hp) with no perceivable loss of throttle response at low speeds/low rpms.
I did the flapper mod and noticed most of the changes written about in the article, so I was pleased with it and kept it.
others have written that they didn't notice a change and put everything back together, so there's that as well.

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post #8 of 8 Old 04-04-2013, 09:26 AM
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yeah it will only work when its under load as the motor will produce enough vacuum then to operate it.

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