When Exactly Is The Flapper Closed???

So this has come up (again) on SMJ.
I'm reading different theories and interpretations of flapperology as I search through forums.

When is the flapper closed? We know it's open most of the time. At idle, and when bike is off especially.

Do we KNOW, without question, when it's closed?

And how do "we" know this?
Is it just repeating what we've read on other forums?

What's your source for flapper information?

I can only repeat what I've heard others say.

I'd love a definitive, non-debateable source if there is such a thing.

There's this video, but i can't tell what he's doing.

https://www.youtube.com/watch?v=G3mXn2tl9N0

yep...saw that.

It shows nothing really. Bike is not even running. He's either pulling vacuum on hose, or simply manipulating by hand.

I wonder if the flapper moves on dyno runs? Especially rear wheel dynos?

So are most of us just "lemmings"?

Are we all just parroting what we've read from others?

Would Yamaha really design something to choke off air under hard acceleration?

I read where one guy thought it closed on deceleration. That makes a bit more sense to me.

Could it really only be for noise? The bike is damn quiet when stock already.

I admit completely that I just followed what the majority seem to say and think.

I hope it's not possible the majority isn't misinformed.

motokid wrote:

I hope it's not possible the majority isn't misinformed.

Do you write softare?

HF tested it. I took his word for it since I didn't really give a shit what it did, I just wanted it off my bike.

He put his bike on a stand, put it in gear and rolled on the throttle. It didn't seem tied to the throttle, but tied to the speed of the bike. When the bike got past 20-30 mph it started to close. At least that's what he said. I tore mine off my brand new bike before I even started it, so I never checked when it closed. Didn't really care.

Who is "HF"?

Member that goes by the name of HighFive.

If it ain't on the bike to silence intake noise, I would be very surprised.
That's the reason you see things like inlet snorkels piled on top of the airboxes on the off-road versions of the motocross bikes (like comparing the plugged-up off-road (legal for approved trail use in stock form) WR-250F to the not-too-pluged-up motocross YZ-250F.
Street-legal bikes are far worse.

If you're looking for some kind of official certificate with frilly ornaments on the boarders explaining what it's doing there, write Yamaha Motor Corp., USA a letter. :)

YZEtc wrote:

If you're looking for some kind of official certificate with frilly ornaments on the boarders explaining what it's doing there, write Yamaha Motor Corp., USA a letter. :)

Letter will be in the mail on Monday.

Inform us of any response. :)

I would have to be dead, or damn close to it to not post any response I might get.

I'm not holding my breath though....

Isn't it to restrict the air flow to not run so lean at high rpms? I mean its more power that way, but it also runs hotter and therefore possibly causing more wear? Just a WAG... I am leaving mine on for now ...

0007onWR wrote:

The flapper is a noise emissions item, it will close
in a certain gear at a certain speed at a certain throttle opening
It
will only close when the factory want's it to so the bike will pass
noise emissions, what it wont do is close at full throttle in top gear
etc etc
It's very specific
Lot's of bikes have stuff like that,
the last version of the R1, if you held the throttle in one spot for 10
seconds in second gear the bike would not rev up unless you changed
gears, it's just a trick to make the bike legal
The flapper wont make
the bike run lean or rich and it wont limit power, what it does is
allow the bike to have full power 99% of the time and maybe it could
decrease power slightly in very specific conditions but I cant imagine
anyone feeling a loss of power If it closed at 1/2 throttle in 3rd gear @
30mph
If anyone has access to the EPA testing regs you could
reproduce it at will

And you know this how? What is your source?

Quote :

And you know this how? What is your source?

You are correct .... my guess was a bad guess ... I found this later ...

Should have included it after ... oops ...

https://wr250rforum.forumotion.com/wrr-x-general-discussion-f3/nice-article-from-nz-t2514.htm

I will have a letter in the mail to Yamaha USA this coming Monday.

I hope to get information straight from them on this.

The article you linked says this:

Quote :

In the top of the airbox are the usual nostrils with an interesting
extra – a vacuum actuated flap. At low throttle, high vacuum, when the
motor is not using a tremendous amount of air, ie 100 kph cruise, the
flap shuts off one nostril to quiet it up. This increases rider comfort
and helps it meet Euro III drive-by noise tests.

I'll post Yamaha's response...if I get one.

0007 just pawn in great game of life
But I can tell you why manufacturers don't put this stuff in print
If a manufacturer employs a trick to get I past EPA then it would suggest that it does not comply with noise emissions requirements
I would be surprised if a definitive answer came from any manufacturer for a question like this one
It's don't ask don't tell and we should all be happy we don't have worse legislation to deal with

A guy at SMJ said he once did a dyno project around the intake crap.

He said he got 0.8 whp increase with flapper glued down.
He said another 1.5 whp came with really opening up airbox

Total - 2.3 whp increase can be realized with nothing but free modification to flapper/intake side of the equation

Based on this one guys personal experience.

That is peak hp gains? But what about mid-range and low-end? I would like to see the numbers across the board???

Here's his response:

Quote :

My opinion is not relevant but the data I collected from the dyno is. gutting all that shite is over 2whp gain. It's not in one spot either it pretty much makes 1.5-2whp everywhere.

He's since turbo'd his wr. I asked him if he still has any of the dyno data but have not heard back yet.

James Bond wrote:

Lot's of bikes have stuff like that, the last version of the R1, if you held the throttle in one spot for 10 seconds in second gear the bike would not rev up unless you changed gears, it's just a trick to make the bike legal

Seriously ? I'm not sure about that. ...at least on my 07.

I can hold it at a steady RPM for ten seconds in any gear and if I wick it on, trust me it will change RPMs.

...otherwise, her flapper shuts when mine is open.

Oh dear gawd....

I don't know what it does but I am in the tiny "I'm not touching it" camp. I put a fuel controller on my bike to smooth it out and to wake it up a little. Which it did.
I get awesome mileage like this (65-75mpg) and the bike has enough torque to cruise in 6th at anything over 50mph. And enough acceleration to beat most of the cars around in the stoplight drag sessions everyone participates in on this island. If I need more power and worse mileage I'll jump on my Buell.

tee hee hee...