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The Crazy Hungarian
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Discussion Starter #1
Hi!
I have a problem with the ISC valve. I know i have a 750, but the 1000 has this thing two years now and i thought i try here. My bike throw the C40 code after 1-2 minutes i start riding it or i rev it over 7-8000 rpm. The bike has no idle after that until i start cruising again at relatively slow pace 30-40 mph low Rpms. If i turn the bike off and turn back on it has idle and no code, then the code comes again....
Anyone had a similar problem? Every idea is appreciated. I just want some general ideas before i start taking apart and check it.:cheers

Thanks
 

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The Crazy Hungarian
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Discussion Starter #2
BUMP

Nobody had problem with the ISC yet? Other than the recall?:scratch
 

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Dreaming of buttsecks for years...
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What is the ISC? Don't see the code C40 in the older manuals.....
 

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Hey, I own a 2007 gsxr-1000 no longer under warranty and I'm having the same problem. I rode it for a while trying to isolate the problem and figure out exactly when the light pops on and it mostly happens when I downshift hard. Then if I let the rpms drop to low(pull in the clutch) it will stall unless I blip the throttle a couple times then it will drive poorly but still idle. If anyone has any info on how to get rid of this c-40 isc valve problem Please help! I took my bike back to the dealer last year to have the recalled isc valve "fixed" and it worked for a while but it seems the new valve isn't so great:wtf. My bike has a bmc air filter with a full yosh exhaust and a pcIII. If I manage if figure it out I'll let everyone know.

DEALERS SUCK, THIS BETTER NOT COST ME ALOT OF MONEY!:banghead
 

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The Crazy Hungarian
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Discussion Starter #9
Hey, I own a 2007 gsxr-1000 no longer under warranty and I'm having the same problem. I rode it for a while trying to isolate the problem and figure out exactly when the light pops on and it mostly happens when I downshift hard. Then if I let the rpms drop to low(pull in the clutch) it will stall unless I blip the throttle a couple times then it will drive poorly but still idle. If anyone has any info on how to get rid of this c-40 isc valve problem Please help! I took my bike back to the dealer last year to have the recalled isc valve "fixed" and it worked for a while but it seems the new valve isn't so great:wtf. My bike has a bmc air filter with a full yosh exhaust and a pcIII. If I manage if figure it out I'll let everyone know.

DEALERS SUCK, THIS BETTER NOT COST ME ALOT OF MONEY!:banghead
Finally someone! :shifty Yes, i have the same issue when i downshift and the light pop on @ hard engine braking. Do you have any aftermarket accessory, part on the bike what might interfere with the electrical system? Likie Power commander, quickshifter, anything?
 

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I have the full trc race exhaust system( no cat). I do have the powercommander(pcIII) but I wouldn't have guessed it would cause the FI light to pop on because I have had it installed 3 weeks after I bought the bike last april and I didn't start having a problem with the light coming on until like 4 weeks ago. It used to come on only once in a while so I would shut it down and fire the bike back up and everything would be ok but now I can't ride it for 5 min. without it popping on.

I also went to the dealer today..... absolutely no help!! They said they haven't seen this problem before and they would have to call up suzuki to find out what to do. Screw them. I think I'll call suzuki myself.
 

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I called dynojet. They said if it was the powercommander, the bike would have thrown a c32 code for the fuel injectors. The isc valve has nothing to do with the powercommander. I knew the pc3 wasn't the problem b/c I have had it installed on my bike way longer than I have had this problem. back to square one.....
 

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The thing that pisses me off is that I can rev the crap out of it in my driveway and the light wont come on but as soon as I'm on the road and tap through the gears, then it comes on. I just want to ride, give me a break god. I even pulled out the ISC valve to see if it was operation correctly when I keyed the ignition and it does.(it's supposed to close when ignition is turned on and open full then return closed when key is turned off) The ECM better not be screwed up b/c they cost like $650.00.....ouch.
 

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The Crazy Hungarian
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Discussion Starter #16
The thing that pisses me off is that I can rev the crap out of it in my driveway and the light wont come on but as soon as I'm on the road and tap through the gears, then it comes on. I just want to ride, give me a break god. I even pulled out the ISC valve to see if it was operation correctly when I keyed the ignition and it does.(it's supposed to close when ignition is turned on and open full then return closed when key is turned off) The ECM better not be screwed up b/c they cost like $650.00.....ouch.
Yeah, same thing. It does ONLY on hard engine braking. I tried to do on the rear stand using the rear brake as a load. I did nothing but baked my rear pads. As soon as i get for a ride at the first hard engine braking I get the code. If i ride smooth no code comes up. I tried to disconnect all my gadgets and still did it. I checked with the SDS and everything seems to be OK. It's weird that the Idle speed is absolutely not adjustable. Actually it is by the small screw on the TB but it's almost impossible to get to it. My exact code is "Idle speed is higher than the desired idle speed" C40 P0507.
My idle speed was steady 1200 rpm. Now I raised it to 1400 rpm by the screw. I will do a test run around the block with the SDS strapped to the bike with my laptop on my backpack, and i want to see the log of all the sensors when it's happening. Especially I want to see the ISC steps.
 

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How did you get and SDS?! I want one and can't find one, please help me get one. Email me so we can talk about that.

anyway I figured my bike out! yes! so here it goes... I bought a brembo clutch master cylinder and it didn't have wire hook ups for the clutch wires like the original so I just spliced the wires together b/c there was no where to put them(what other option did I have). By doing that the ECU thought my clutch was disengaged all the time..this screwed up the computer. I don't know why it gave me a c40 code but it did. In conclusion I cut the wires and installed a switch so I have to flick the switch ON every time I want to start the bike and flick it off after the engine starts.( kind of a hassle but what can I do) IF YOU LOOPED YOUR CLUTCH WIRES TOGETHER, CUT THEM APART LIKE IT WAS ORIGINALLY !!! and your bike should run 100% again. Mine does.

If your problem continues then I read in another forum you may need to upgrade your firmware on your pc3. Call powercommander for your model. It should get rid of the FI code. I have the upgrade but I have a 2007 gixxer 1000 and I don't know if its compatible with your 08 750. Let me know how it turns out anyway.
 

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correct idle for my bike is 1050rpm plus or minus 100rpm. I would check your manual cuz 1200rpm seems a little high and 1400rpm, I would think is way too high. My buddy has the gsxr600 and his idle is like 1100rpm. Maybe your right but personally I would check the service manual.

If you find out your idle is to high. You don't have to mess with the screws on the throttle body, just open your pc3 fuel map on your laptop, go to the 2% throttle open row and follow it down to the 1000-1200rpm rows and lower the values until it idles right. I don't know why I'm explaining this, you have an sds tool, if you figured that out I'm sure you already have your pc3 figured out. All I know is that if your pc3 is set to high and ECU set to low then they fight each other and you'll get and FI code.
 

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The Crazy Hungarian
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Discussion Starter #19
Very interesting....
The clutch switch thing. Sounds impossible, but never know what the little Japanese Suzuki engineers did with the new computer software :) I have the CRG GP clutch and I spliced the wires together. I did lots of mods at the same time so i did not have a real chance to sort this out. Definitely before I did the CRG clutch the bike did not do the C40. I got the SDS tool by mistake fro a Suzuki dealer. The parts guy didn't know that he not supposed to order for me, and I got it :)
I don't think I can get you another one... It's like $600 or more plus the software another $150.
I do not have PCIII. I have other stuff on the bike, but I bypassed and did the same thing. I'll try the clutch switch tomorrow. I hope it will help.
BTW the Idle on the '08 750 supposed to be 1200 +/50 rpm. This is what set by Suzuki in the ECU. I like to have higher idle speed on the track anyway.
 

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The Crazy Hungarian
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Discussion Starter #20
MotoGP bikes idles around 3000 rpm :punk
 
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