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Old 04-25-2011, 11:34 PM   #1
UDKM
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Default -C28 options

Hi all, I've been doing some reading thru the forums and seems everything I've read on this code(secondary throttle actuator) the bike experiences loss of power but that's not the case with my bike. How do you know for sure it's a bad STVA and are there other common issues that are linked to that dealer code error? And will it leave NE stranded if I take it out again before a fix?

Edit: title should read 'options.'
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Old 04-25-2011, 11:45 PM   #2
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what it dose is it controls the secondary throttle butterflies ,they are computer controled to open at around 7k rpm and I have heard of people removing the actuator when removing the butterflies and causing this issue when they put it back motopsyco had this problem I think too ,I dont think it will do any thing other then open the butterflies early or late so only a lil mpg issue or small horse power issue -I removed the butterflies and never touched the actuator and never got a code but I think you are safe just the light is an inconvience
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Old 04-25-2011, 11:53 PM   #3
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what it dose is it controls the secondary throttle butterflies ,they are computer controled to open at around 7k rpm and I have heard of people removing the actuator when removing the butterflies and causing this issue when they put it back motopsyco had this problem I think too ,I dont think it will do any thing other then open the butterflies early or late so only a lil mpg issue or small horse power issue -I removed the butterflies and never touched the actuator and never got a code but I think you are safe just the light is an inconvience
I'm attempting to make a bypass unit for the c28 code... i found a schematic on how to do it. If it works (I'm a noob at electrical boards) I can make another, pm me if you're interested. It basically tricks the computer into thinking the STVA is still there and functioning properly.
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Old 04-26-2011, 12:01 AM   #4
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I'm attempting to make a bypass unit for the c28 code... i found a schematic on how to do it. If it works (I'm a noob at electrical boards) I can make another, pm me if you're interested. It basically tricks the computer into thinking the STVA is still there and functioning properly.
but why take the STVA off? I just took off the butterflies and let the actuator do its thing since it is not hooked to the blades any more it does nothing?if it never failed then why remove it ?if it threw the code its just cause the blades are sticking or it has been adjusted to the wrong position
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Old 04-26-2011, 12:14 AM   #5
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but why take the STVA off? I just took off the butterflies and let the actuator do its thing since it is not hooked to the blades any more it does nothing?if it never failed then why remove it ?if it threw the code its just cause the blades are sticking or it has been adjusted to the wrong position
mine has failed miserably... last tuesday my bike was under three feet of water when my garage flooded. When i took it apart, water poured out of it and I cleaned it, made sure all connections were good, but it still doesn't pass the manual electrical tests. It seems every 2nd or 3rd time I start the bike C28 shows up, and it doesn't function properly... I did take the butterflies off but I hate seeing that damn light lol

I've also gone over every single electrical connection on the bike and ran continuity tests on the STVA, no shorts in the wires either.

Last edited by matt750gsxr; 04-26-2011 at 12:16 AM.
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Old 04-26-2011, 12:19 AM   #6
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mine has failed miserably... last tuesday my bike was under three feet of water when my garage flooded. When i took it apart, water poured out of it and I cleaned it, made sure all connections were good, but it still doesn't pass the manual electrical tests. It seems every 2nd or 3rd time I start the bike C28 shows up... I hate seeing that damn light lol
did you take the air box off and see if the butterflies are sticking ? or try to run it with the box off to see if they are opening at all? or if they might be a lil out of wack ?
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Old 04-26-2011, 12:24 AM   #7
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if you remove the STVA and trick the computer in to thinking it is still there then you need to remove the butterflies to or you will be killing you power and flooding you cylanders do to not enough air in the system cause they will never open
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Old 04-26-2011, 12:25 AM   #8
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did you take the air box off and see if the butterflies are sticking ? or try to run it with the box off to see if they are opening at all? or if they might be a lil out of wack ?
Yeah I've had the airbox off, sometimes they run through the correct starting procedure. Most times it closes from 20% to full close, then opens to full open, but doesn't go back to 20% open. The motor isn't reversing itself once it opens all the way. I spent 6 hours screwing with it today. The STVA has all new lithium grease on its gears, the cables are perfect, and the butterflies open and close with ease if I take the cables off to do it by hand.
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Old 04-26-2011, 12:26 AM   #9
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if you remove the STVA and trick the computer in to thinking it is still there then you need to remove the butterflies to or you will be killing you power and flooding you cylanders do to not enough air in the system cause they will never open
Butterflies are already off
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Old 04-26-2011, 12:33 AM   #10
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sounds like its out of adjustment and cant find how to reset to -0- but I think you have the right idea to just say f it as I luv the way it runs with out the butterflies so much less engine breaking and herky jerky and I bet its even better on your bike cause you dont have the drastic gearing like I do

will done bro way to take matters in to you own hands

and to the OP I hope some of this helps
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Old 04-26-2011, 12:40 AM   #11
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Yeah I love the way it feels without them in there... and as soon as the light goes away I'll be a happy camper again
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Old 04-26-2011, 07:18 AM   #12
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Originally Posted by outlaw750 View Post
what it dose is it controls the secondary throttle butterflies ,they are computer controled to open at around 7k rpm and I have heard of people removing the actuator when removing the butterflies and causing this issue when they put it back motopsyco had this problem I think too ,I dont think it will do any thing other then open the butterflies early or late so only a lil mpg issue or small horse power issue -I removed the butterflies and never touched the actuator and never got a code but I think you are safe just the light is an inconvience
right around 7k makes sense... didn't seem to matter what gear or how fast or slow I was going but was in higher rpms and thought it might have something to do with the temperature. What do the butterflies controlling? Air flow or gas or both? I'm not familiar w mechanics in that detail.
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Old 04-26-2011, 11:19 AM   #13
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The stc system (valve, actuator, stps, stcu) gets it's input from the ecm depending on which of the 8 maps the ecm is using at any given time.

Low speed/rpm = mostly closed stv
High speed/rpm=mostly open stv
WOT=Wide open stv



the top butterflies are the ones we are talking about they control air flow below 7k rpm if you remove them they will look like the pic below



here is a link from when I did mine http://www.gsxr.com/showthread.php?t...ht=butterflies
hope this helps
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Old 04-26-2011, 08:15 PM   #14
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Oh that's awesome reference - thank you! I'll have to open it up and give it a try. Doesn't look very difficult at all. I rode it tonight and the F1 error definitely kicks in when I riding it in higher rpms.
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Old 04-26-2011, 08:30 PM   #15
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Oh that's awesome reference - thank you! I'll have to open it up and give it a try. Doesn't look very difficult at all. I rode it tonight and the F1 error definitely kicks in when I riding it in higher rpms.
yea it sounds like they are not opening up all the way -I would run it with out the airbox and rev it up and hold it at like 8k to 10 k and see if they are all the way open you should be able to see this with out removing the whole air box just open the cover like you were gonna change the air filter -good luck let me know what you find out
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Old 04-29-2011, 07:16 AM   #16
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Didn't you just buy the bike last year? If so, I would assume there is still warranty left in which case I'd drop it off at the dealer and tell them to fix it properly.
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Old 04-29-2011, 01:39 PM   #17
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Well funny I hadn't thought of that but yes, I'm pretty sure I have a 2yr on it will give them a call and see if it's covered. TY!
Was sorta looking forward to ripping it apart. Sorta. Well not really lol. Prefer to be riding it.
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Old 04-29-2011, 01:42 PM   #18
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Well funny I hadn't thought of that but yes, I'm pretty sure I have a 2yr on it will give them a call and see if it's covered. TY!
Was sorta looking forward to ripping it apart. Sorta. Well not really lol. Prefer to be riding it.
As long as my vehicles have warranty, I let the "professionals" fix it
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Old 07-26-2011, 09:00 AM   #19
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I thought I'd update everyone on this issue cause it ended up being something different to all the previous F1 threads I've read.

I took the bike to the dealer because I do have an extended warranty on it. Of course when they opened the bike up (gas tank) to check it the light would not come on. They spent 3 hours looking and plugging unplugging etc... and nothing. For me it never failed that the light would turn on as soon as it hit 6500rpms yet the bugger didn't want to do it at the dealer. I requested he give it a spin on the road to see if he'd get the light.

After giving it a run (and no light) he noticed the bike recycled for a 2nd time when he was taking the key off, which it shouldn't do. That was weirder. SO he opens up the tank area again and takes another look. Pulls a bit further out the connector(with wires) that plugs into the STVA and noticed a tiny nick in a wire. That wire just happens to be the one that would give the C28 signal. That small nick was making contact with the frame and so that was causing the interference. It was making the bike use more gas because it's what triggers that function. Hope that makes sense. Anyways, all it needed was that cable to be heat wrapped so it wasn't exposed and causing the interference. So it was never really a C28 error but it was getting the signal because the faulty wire was making contact. Ok I think I said the same thing at least twice

The harness doesn't have much wiggle room in that space between the frame and the tank so it's likely to happen to someone else as well. Hope that helps someone out.
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Old 07-26-2011, 09:22 AM   #20
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Originally Posted by UDKM View Post
I thought I'd update everyone on this issue cause it ended up being something different to all the previous F1 threads I've read.

I took the bike to the dealer because I do have an extended warranty on it. Of course when they opened the bike up (gas tank) to check it the light would not come on. They spent 3 hours looking and plugging unplugging etc... and nothing. For me it never failed that the light would turn on as soon as it hit 6500rpms yet the bugger didn't want to do it at the dealer. I requested he give it a spin on the road to see if he'd get the light.

After giving it a run (and no light) he noticed the bike recycled for a 2nd time when he was taking the key off, which it shouldn't do. That was weirder. SO he opens up the tank area again and takes another look. Pulls a bit further out the connector(with wires) that plugs into the STVA and noticed a tiny nick in a wire. That wire just happens to be the one that would give the C28 signal. That small nick was making contact with the frame and so that was causing the interference. It was making the bike use more gas because it's what triggers that function. Hope that makes sense. Anyways, all it needed was that cable to be heat wrapped so it wasn't exposed and causing the interference. So it was never really a C28 error but it was getting the signal because the faulty wire was making contact. Ok I think I said the same thing at least twice

The harness doesn't have much wiggle room in that space between the frame and the tank so it's likely to happen to someone else as well. Hope that helps someone out.

Great information man. I'm glad you got it fixed. It always ends up being something simple lol.
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