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Discussion Starter #1
So I woke up early today and couldnt fall back asleep so I decided to change the plugs on the bike and sync my throttle bodies. I replaced the plugs but didnt have time to build my homemade throttle body sync tool...so thatll get done tomorrow...hopefully. Anyway, while I had the airbox off I cycled the key and noticed my secondary butterflies cycle themselves and stop at fully open. I dont think this is correct...is it?? Heres a video:

https://www.youtube.com/watch?v=OHklMTdthX4&feature=youtu.be
 

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ill doublecheck mine when I get home - pretty sure they're fully open too, but it doesnt look like yours are cycling closed, and then back to open, which I would have expected
 

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mine do exactly the same thing

you can turn them by hand, so they're fully closed (I do this when airbox is off, to keep shit from falling in), and they turn back as per your video, so the vane is vertical on turning the ignition

so think you're ok..!
 

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Discussion Starter #6
Cool. Thanks man! Its kinda strange tho cause every other video ive seen they are in a closed position when the ignition is on.

I was reading up on their purpose and function...it said they prevent engine bogging when the rider cracks the throttle open too quick and lets a bunch of air into the engine. Altho I cant understand how it will do that if its in a full open position. Maybe they go to the closed position when the engine is started??
 

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I think if you whack open the throttle, the subthrottles will close to limit the rush of air - sort of like a buffer to the power delivery. Possibly on other bikes, the subthrottles just lag behind the normal throttle (so whack open the throttle, and the subthrottles open too, just slower) - I'm unsure though


its a fairly common mod to remove them actually, but you might need a power commander tune to take some of the harshness out of the throttle response
 

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Discussion Starter #8
Hmm u might be right. They also act like a choke and open up when the bike is cold just to get the engine up to operating temp. My bike was cold when I tested it out so thats what might be happening actually. Im not gonna have a chance to test it for the next 2 days tho. Ill report back when I test it out!
 

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Hmm u might be right. They also act like a choke and open up when the bike is cold just to get the engine up to operating temp. My bike was cold when I tested it out so thats what might be happening actually. Im not gonna have a chance to test it for the next 2 days tho. Ill report back when I test it out!
Um doesn't choke mean they close to limit the air, hence the word choke
 

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yea no choke Im afraid

ecu just runs the injectors longer to run the engine rich during warm up (causes the 'fast idle' the bike usually starts with, before it settles down to normal idle speed)
 

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Discussion Starter #12
yea no choke Im afraid

ecu just runs the injectors longer to run the engine rich during warm up (causes the 'fast idle' the bike usually starts with, before it settles down to normal idle speed)
Ahhh so thats how it works eh? I assumed it opens up and thats what causes the higher RPMs at startup.

Well if thats the case it seems like both of our bikes are busted lol.
 

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Discussion Starter #13
In the meantime if anyone else can visually check how their secondary butterflies work and report back that would be great!
 

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Troooolling!.....:nana:

Just FYI: Chokes are used with carburetors. They are used to increase the pressure drop across the main fuel jets between the venturi and the fuel float chamber. This causes more fuel to be drawn into the intake thus increasing the fuel to air ratio. The increase is needed for one major reason. The cold engine, the cold carburetor and (in the case of cars) the long cold intake manifold won't support the evaporation of poorly atomized fuel coming from the idle ports of the carburetor. The fuel literally condenses onto these cold surfaces robbing the engine of fuel. The choke cuts off air thus increasing the F/A ratio and creates a relative vacuum at the venturi to draw more fuel into the intake manifold. This increases the amount of fuel that actually evaporates and makes it into the cylinders. Once the pistons, the intake valves, the head, the manifold (if present) and the carburetor body starts warming up, fuel evaporation gets better and the F/A begins to increase and now more air is needed so the choke needs to open up.

Electronic fuel injection makes a choke unnecessary. The F/A is controlled by the ECU which is aware of the temperature. The injectors are mounted close to the intake valve which warms up very rapidly. The injectors are much better at atomizing the fuel which makes for faster evaporation. The ECU can even fire the injector while the intake valve is closed (on the power stroke) to create a pre-charge of F/A that will be drawn in as the valve opens. The engine runs much better because control the the F/A mixture is much more precise.

Okay. Done trolling....:sleeping:
 

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mine do exactly the same thing

you can turn them by hand, so they're fully closed (I do this when airbox is off, to keep shit from falling in), and they turn back as per your video, so the vane is vertical on turning the ignition

so think you're ok..!
Um....i'm pretty sure you do not want to do this.....I believe that could mess with the calibration of your TPS (Throttlebody Position Sensors)...someone correct me if im wrong? :O
 

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Part of the procedure for testing the sub-throttle sensor (as per the 2009-2012 manual) involves opening them by hand. I would ASSume that would mean you're probably OK to close them.

I'd do it slowly though, to take it easy on the actuator.
 

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Discussion Starter #17 (Edited)
Ok so I decided to tackle my subthrottle situation today. Turns out they are operating fine :bigthumb: Heres what happens when the bike is warmed up. The valves start in the open position then slowly shut themselves. After that it works like its supposed to. I havent seen any other videos of other bikes doing this same thing....but it works! So fuck it...Im not messing with it.

http://m.youtube.com/watch?v=gE7wcV5AnQ8
 

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Nice. It could be the other videos I watched were of warmer bikes? Lol I don't know... The closest I've ever been to this part of my engine was plugging in the power commander's injector wires.
 
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