K7 throwing C40 code I may have finally solved it!! - Suzuki GSX-R Motorcycle Forums Gixxer.com
 
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post #1 of 6 (permalink) Old 07-23-2018, 01:40 PM Thread Starter
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K7 throwing C40 code I may have finally solved it!!

So I've been struggling trying to find out the reason my bike is intermittently throwing a C40 code and stalling when the clutch is pulled in. I have Brembo billet clutch master cylinder with a Brembo micro switch. And I know you can't just install the Brembo master cylinder without a clutch switch or it most likely throw a C40 code. I was hoping this would be an easy fix. So I replaced the Brembo micro switch thinking it may be the issue. But unfortunately that didn't fix the problem. I then replaced the ISC valve which is related to the C40 code. I thought this fixed the problem but after about 200 miles of riding the C40 came back. But this time I was able to notice it happened while downing for 3rd to 2nd gear at around 6,000 rpms. Shorty after the C40 appears when I pull in the clutch the bike stumbles and stalls. But it always restarts without any issue. So I decided to see if I could get the code to reappear by downshifting quickly from 3rd gear into 2nd at approximately 6000 rpms. And there it was the C40 appeared and as I pulled in the clutch the bike stumbled and stalled. I restarted the bike without any issues and did the same test again. This time it a few tries but the C40 did appear and again the bike stalled when the clutch was pulled in. At this point I thought maybe the new ISC Valve needed to be set with the SDS tool per the repair manual. Although my local Suzuki dealer informed me to just disconnect the battery before I install it and I should be fine. But I'm out of ideas so I figured setting the ISC Valve per the repair manual might fix it. But last night after doing more research on the internet one guy stated he had the same setup and noticed the lever was releasing the switch immediately when the clutch lever was pulled. He stated the switch was to sensitive (which I really don't now how) so he switched to a Brembo hydraulic pressure switch. Unfortunately he never confirmed if it fixed the issue. So contacted HardRacing today where I purchased the setup and questioned if they knew of any issues with the switch setup. They said they didn't know of any but the switch setup was no longer available. I then asked what they were selling for the K7 knowing the clutch switch needs to be in place. They said everyone is using a Brembo hydraulic pressure switch. So then I went through all my original parts and found the factory clutch master cylinder with my ASV lever and factory clutch switch. I noticed the switch isn't fully released until the lever is pulled almost half way in. I then compared that with my Brembo setup and ASV lever. Now when I pull in the clutch it immediately releases the switch. So I adjusted the Brembo master cylinder so it releases the switch as late as possible when the lever is pulled in. The Brembo master cylinder doesn't allow me to get the lever to release the switch halfway through the pull. But its better than it was so I then took the bike out and tried down shifting from 3rd to 2nd gear from 6000 to 6500 rpms and no matter how many times I tried I couldn't get it to throw the C40 code and stall. Not sure if this is the fix I needed but it may be.... Any thoughts would be appreciated. Thank you for your time...
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post #2 of 6 (permalink) Old 07-23-2018, 02:34 PM
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Re: K7 throwing C40 code I may have finally solved it!!

There are a number of posts here about the engine dying and immediately restarting that were related to the clutch switch. This is one but there are many others. They were associated with disabling the switch but it wouldn't surprise me if late or early actuation caused similar problems. If you have it, I'd be looking at the OEM lever & switch to see how it compares with what you now have.

This is why I said early on that I was glad that my K6 doesn't have an ISC.
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post #3 of 6 (permalink) Old 07-23-2018, 03:34 PM Thread Starter
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Yes I do have the original setup. And the switch is release half way through the pull. My brembo setup now is close to a 1/4 way through the pull before it releases the switch. That’s the best I can do with the current setup. So far no C40 code. If it does come up again I already have a brembo hydraulic pressure switch I can wire up and test. If that fails I’ll put on the factory setup again. Which will suck because the brembo setup was close to $600!! We’ll see...
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post #4 of 6 (permalink) Old 07-23-2018, 08:00 PM
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Re: K7 throwing C40 code I may have finally solved it!!

If the problem comes up again, you could always try the OEM lever as a test. I'm not a fan of pressure switches but sometimes you just have to. Also, you ought to be able to elongate the switch mounting holes to adjust the trip point. It should be possible to do it in a reasonably workmanship manner, say by using a suitably sized carbide burr and a drill press.
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post #5 of 6 (permalink) Old 07-24-2018, 02:54 PM Thread Starter
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Took it out today and put 70 miles on it. Tried downshifting from 3rd to 2nd at 6500 rpms quickly and still no code C40. I’m starting to think it may just be fixed with the simple adjustment of the brembo master cylinder. Time will tell...
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post #6 of 6 (permalink) Old 07-26-2018, 11:39 AM Thread Starter
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Just one more update on the C40 code. I’ve ridden the bike another 100 miles and the C40 code hasn’t reappeared. I’ve tried downshift into 2nd and 3rd gear at Rpms over 6000 and everything seems fine. So at this point I’m convinced the bike is finally fixed. Thanks everyone for your help. Hopefully this post helps someone
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