Flapper valve 919 - Wrist Twisters
 
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post #1 of 7 Old 10-31-2008, 04:05 PM Thread Starter
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Flapper valve 919

I looked at it today. I was open when I started the bike and i reved it up and it never closed. I when for a ride and checked it and it never opened. I checked the hose connections. they were fine. So when does it close? The bike is in the Canadian market.

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post #2 of 7 Old 10-31-2008, 04:15 PM
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Quote:
Originally Posted by Kingston View Post
I looked at it today. I was open when I started the bike and i reved it up and it never closed. I when for a ride and checked it and it never opened. I checked the hose connections. they were fine. So when does it close? The bike is in the Canadian market.
Umm .. Ok if this bike has the flapper mod done to it . It will never close. If it dosn't then it is supposed to stay closed until you hit around 5 grand on the tac .Other than that I cant rly say, the above post is a little confusing ...




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post #3 of 7 Old 11-01-2008, 04:58 AM
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So, it was open when you started it, then closed when you rode it? What seems to be the issue? Not sure I understand your question.

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post #4 of 7 Old 11-01-2008, 05:35 AM
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The flapper valve is operated by vacuum. An internal combustion engine will create the highest vacuum on hard deceleration with the throttle closed. I think there is some myth out there about the flapper closing at 5,000 RPM. In reality, the higher the RPM in the engine, the lower the vacuum. I did the flapper mod (disconnected and capped of the vacuum hose) to my bike a few weeks ago. What I immediately noticed was smoother deceleration. My belief is that the flapper acts like some sort of rudimentary Jake Brake by starving the engine for air and causing it to decelerate faster while engine braking. To see it actually 'flap' you will need to take off the side covers, find an empty road, and stretch your neck way to the left while rolling on and off the throttle at various speeds.

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post #5 of 7 Old 11-01-2008, 05:49 AM Thread Starter
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I meant to say," I went for a ride and checked it and it never closed ". So it should be closed up until 5000 rpm? I had this bike since new and have never touched this thing. The vacuum hose is attached at the valve but it must not be getting vacuum to close. Maybe the hose is disconnected at the other end. I would like to get it working so I can tell the difference.

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post #6 of 7 Old 11-01-2008, 06:34 AM
 
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i felt an immediate improvement, after i did the flapper mod, ya if i were you i would check to see if the flapper has been disconnected or not

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post #7 of 7 Old 11-01-2008, 11:06 AM
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Kingston, The flapper valve is normally open and will close when a vacuum is applied to the valve. Basically, the more open the throttle is, the less vacuum. Under heavy acceleration, there will be very little vacuum.

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