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Is there a reason Wunderlich says “it won’t fit 2017+ R Nine T”


Everywhere I’ve looked regardless of brand say they fit from 2014-2020. Am I missing something here?
 

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I would guess they’re putting out wrong information there.
Ken.
PS. Do any other BMW bikes other than R9T models have flappers?
 

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Beats me as well because I didn't think anything had changed in this area on the '17 model specifically.
Looks like they’re just summarizing cause apparently it doesn’t fit SOME models...but according to BMW, it’s the same part for LOTS of vehicles (click the tab that shows what vehicles it fits):
 

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Stupid question, what exactly does that flapper valve do? How does it opening or closing benefit the bike, or take away from performance? Is it a pollution control device?

Thanks,
-Tim
 

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Stupid question, what exactly does that flapper valve do? How does it opening or closing benefit the bike, or take away from performance? Is it a pollution control device?

Thanks,
-Tim
Have a read through the thread I've moved your post to. And if you get to the end you have my respect! LOL

My take is that the flapper valve has a negligible effect on performance and is primarily a noise control device. If anything it slightly reduces engine braking and makes the bike a little louder. I removed it as it is ugly and just something else to go wrong. Never looked back...
 
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I think my Pure is too loud with the flapper in and when I removed it on a previous Pure it became unbearably loud for me, so I reverted back.
Ken.
PS. I love the sounds other people’s bikes make, but like my own as quiet as can be....maybe I should go electric o_O
 

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141267

Well, there is a benefit of removing it, there’s a bit more low end without it that you can see in the dyno from 50-70mph...ignore the first two a/f ratios, we couldn’t get a good sniffer reading (the blue and red) with it in place, once we removed the flapper a good a/f reading was received (the green). Set-up is Ti Akrapovic Headers, flapper delete, and GP-1 exhaust.
 

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2018 R Nine T Pure
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I think my Pure is too loud with the flapper in and when I removed it on a previous Pure it became unbearably loud for me, so I reverted back.
Ken.
PS. I love the sounds other people’s bikes make, but like my own as quiet as can be....maybe I should go electric o_O
I have my flapper removed on my Pure, and find that it is rather loud. I might try putting it back on for a bit and see.
 

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I have my flapper removed on my Pure, and find that it is rather loud. I might try putting it back on for a bit and see.
I miss the flap, (When not fitted) the BRAPP on low revs and low speed is excessive for me. Attracts too many head turns when around home streets.
I do live in a built up area.
Ken.
 

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Set-up is Ti Akrapovic Headers, flapper delete, and GP-1 exhaust.
So did you dyno the bike before and then after the flapper delete or did you remove the flapper when you installed the new exhaust system and then dyno the bike?
 

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So did you dyno the bike before and then after the flapper delete or did you remove the flapper when you installed the new exhaust system and then dyno the bike?
I was concerned with the A/F ratio on having a complete exhaust on a stock map more than anything else. I wanted to make sure I wasn’t running lean so I didn’t really pay attention to numbers. But I picked up the flapper valve on the way to the dyno session and we installed it there. Got two runs in with a full exhaust with the flapper, and then a single run deleted flapper.

The flapper itself didn’t give a bump in peak power, it just changed to having better low end power. The graph below in green shows the difference the deleted flapper made to the power curve. You can see the bump in power from 50-70mph, which in the power band is where you would be coming out of a corner. The blue and red lines are the two runs before the flapper delete, which is also why the A/F reading is jacked up on the bottom graph. The flapper made it hard for the sniffer to get a good read. But once the flapper was removed, you can see it runs pretty well on the stock map like Akrapovic said it would....so that’s pretty comforting.

141276


I asked him if the ratio is even remotely bad and he said given the current weather, when it gets nicer out, it’ll be pretty spot on and that a RapidBike EVO, BoosterPlug, or custom map would really be splitting hairs and the juice not really worth the squeeze. I trust him...heis REALLY well respected in the vintage and British motorcycle community. Arguably legendary.
 

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on my '21 scrambler the flapper is welded to the cat, new headers looks like the only way to delete
 

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I plan on undoing the servo cables and safety wiring the valve open. It’ll look stock but make 2% more racket.
 

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on my '21 scrambler the flapper is welded to the cat, new headers looks like the only way to delete
I had heard rumours of this, seems they were true! :( :mad:(n)

Nanny state strikes again....
 
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