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I found a bargain deal on a k6 gsxr 750 , converted to a naked bike with lot of mods. The bike is 60 000 km , in fully drivable condition , but it shows the c28. My plan is to buy the motorbike and take it to repair shop for fixing this f1 c28 (STVA) error. How wise is that , and can anyone tell me how much would approximately cost me that? Thanks a lot
 

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Code C28 is STVA malfunction. Secondary Throttle Valve Actuator. First thing to check is the connector to make sure its together and making contact. Prop up the tank, on the right side of the throttle body (under the airbox) is the STV motor. It's a little black box connected to the throttle body, should have a 4 wire harness coming out of it. Follow the wire to the connector and check it, make sure it's together.

If it's connected and you have a STVA failure that part only comes as part of the throttle bodies, which is very pricey, it's possible to find a used STVA but start with the connection, maybe you will get lucky.
 

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Thanks a lot for the reply. I am wondering, if its Stva failure but can be driven without problem, cse he said he has driven it 6 years with that error, then would I be also OK if I just continue driving like that? Does it entail any risks?
 

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Test the STVA first. The fix the shop will want to do is replacing the throttle body. That'll cost you $1000USD at a minimum. The K6 & K7 STVAs are the first of the newest design and are pretty good, but those models also had a bad charging system. Voltage spikes of that system seem to damage the portion of the ECM that drives the STVA.

Testing the STVA and STPS is pretty simple. All you need is an Ohm meter. It's even possible the previous owner was an idiot and removed/installed the STPS incorrectly. Get a manual and a meter and test it out. A cheap meter can be had for about $20USD, and if you intend to do any work yourself, a service manual is a good purchase.
 

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Thanks a lot for the reply. I am wondering, if its Stva failure but can be driven without problem, cse he said he has driven it 6 years with that error, then would I be also OK if I just continue driving like that? Does it entail any risks?
IIRC The old '98 750 FI system had single throttlebody valves, leading to a jerky throttle response, though somewhat of a complaint, it didn't stop people from riding it
But Suzuki developed a fix for that by adding the STV's on later models
So in basics, the STV are not a necessity, it's just that the bike may feel like having an on/off switch when opening/closing the throttle

(Small addition: the STVA isn't JUST for smoother throttle, it also allowed for better powerdelivery over the entire RPM range)
 

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Yes and no. As long as the system detects an FI issue, it's not going to perform to its full potential. Also, the system has a secondary function of controlling fast idle. So if it's stuck fully open, you're stuck in fast idle. If not, then you're air restricted a bit.
 

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I found a bargain deal on a k6 gsxr 750 , converted to a naked bike with lot of mods. The bike is 60 000 km , in fully drivable condition , but it shows the c28. My plan is to buy the motorbike and take it to repair shop for fixing this f1 c28 (STVA) error. How wise is that , and can anyone tell me how much would approximately cost me that? Thanks a lot
I had the same problem,I removed mine and fitted a servo buddy ,no more c28 code and bike runs fine
 

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Depends if the issue is with the unit or the wiring or with the ECM. If it's the unit, it'll make the code go away. If it's something else, swapping a good part in for a good part doesn't solve anything.
 

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Depends if the issue is with the unit or the wiring or with the ECM. If it's the unit, it'll make the code go away. If it's something else, swapping a good part in for a good part doesn't solve anything.
Mine was the stva itself ,couldn’t get a replacement in the uk ,ridiculous money for a new 1
 

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Discussion Starter #12
OK that's cool. If it's the Stva then I get a servo buddy. What if it's the Ecm or the wiring? What solution is there for these 2? Thanks a lot again
 
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