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Exhaust flap 2015

5K views 18 replies 8 participants last post by  rismmgifyf 
#1 ·
Has anyone removed the rear exhaust flap near the can? I thought I remembered reading about this a while back but can't find a thread on it now. My impression is that the flap upstream near the headers is for needed back pressure, but the one near the can is for noise reduction. Also it is not clear how to remove it and also wondering if it's spring loaded closed or open.
 
#4 ·
I pulled the cables off and took a quick test ride. The transition from off throttle to on throttle is noticeably less smooth so I'm putting em back on. Anyone else notice this?
 
#5 ·
did this to my 14rr and went up in the mountains, it was horrible. lost a bit of engine braking, no good at all.

Those flaps really do a good job. those who remove them and say, wow it sounds much deeper, I always wonder how they can't notice the engine braking reduction. it does sound better though.

the front butterfly is so annoying ticking away. i wish that it wasn't there. its adjusted perfect but its still annoying ticking away.

I also noticed the on -off throttle was noticeably less smooth.
 
#11 ·
Yes, my exhaust is fully Oem. Full exhaust systems don't allow for keeping the flaps.. So thinking on this I'm wondering if the oem fueling map is accounting for the flap at on/off throttle transitions and removing the flap interrupts the system. So in other words maybe the abrupt on/off can be tuned out with more or less fuel.
 
#14 ·
Talked to Yaman at Rapid bike and he said to just ride it for a bit and the RB box should smooth it out. I'm having a hard time wrapping my head around the fact that the thing tunes itself to changes. Anyway, I'm gonna leave the cables unhooked and see how it goes. It sure does sound a bit better at low rpm.
 
#16 ·
I don't know about this bike but on modern cars the computer does learn to smooth out the ride...adjusts to the drivers habits and other external fsctors... Like fuel quality or octane is one example!e. Fuel to air on modern cars adjusts all the time depending on many factors ... On some cars to reset you simply unplug the batter for sometime period.
 
#18 ·
If you don't have a full exhaust with proper tuning it's a good idea to keep servos. I also asked this same question to a BMW master techie and he said RRs in some SBKs races put back the servos or their
equivalent.

I actually disabled 2nd servo by removing bowden cables, I noticed bike was not the same < 5-6KRPM but it sounded richer. I put cables back. Finally, the same techie said for warranty claims that involves anything exhaust without servos will be scrutinized unless the work has been done by a dealership. YMMV.
 
#19 ·
Talked with my buddy who is a long time s100rr rider...The 1st servo near the header should not be removed unless you do a tune... Changes the air flow too much... The second servo near the exhaust is for epa noise requirement. So far that's the consensus from a few I have spoken with... Still rain here so no test for me!!!!
 
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