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My 2010 K1300S made a strange squealing noise at the weekend when I switched the ignition on and the bike ran through its start up checks. It sounded like it was coming from the exhaust link pipe near the servo motor so I assumed it was the flap maybe needing a bit of lubrication.

I removed the end can and looked inside to see the flap in the position below (closed) - this was with the ignition off before I had put the key in
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I sprayed it with WD40 a number of times whilst pushing it with my finger to free it off, it felt quite stiff but eventually when I switched the ignition key on the flap opened. It did not close at this point though, as far as I recall.

So I then sprayed it with white lithium high temp grease and switched the ignition on again and thankfully the noise was gone. However the flap now sits in the position below with the ignition off. When you switch on the flap closes then opens again and remains in that open position.

My question is this - when the end can is removed and you look into the pipe where the flap is with the ignition off, what position should the flap be in? Like mine - open? And then when the ignition key is inserted and turned should the flap then do what mine does - close then open? I hasten to add this is all with the engine not started, only with the ignition switched on.

I just find it a bit strange that when I first removed the end can, the flap was in the closed position. But after lubricating it it now sits in the open position.

Any advice greatly appreciated.:)

How mine sits now with the ignition switched off:-

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I would love to hear what it does. I suspect is is a pollution control device and it constricts exhaust pipe causing higher back pressure, less exhaust cylinder gas clearing so that some exhaust gas stays in cylinder to be fully burned next stroke. But thats a guess.
Dennis
 

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BMW K1200S
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Having just had my K1200S exhaust off recently I can confirm it’s not on that version - the only additional item is the Lambda sensor (same as K1300)

if it was on a Jaguar F-Type I’d say it was the ‘Loud’ flap that opened a bypass to allow the exhaust to sound a bit more fruity. In this case I think you maybe correct.
 

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2009 K1300S, 2017 S1000R
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It is not an air pollution device. It helps with low end torque and as a side issue does modify the noise. It opens wide of course as power demand goes up.
 

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I agree with Beech. My BMW X3 has a similar flap in the exhaust controlled by a vacuum actuated motor. It's in the open position with everything turned off. When you start the car the flap closes and when accelerating the flap opens. It's mainly a noise reduction thing to pass the noise test that vehicles have to pass going by a test "microphone" at a certain speed. Yamaha started putting these on bikes a long time ago to help with low end power and other manufactures have similar devices.
 
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