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C28 STVA problems 600 k3

1406 Views 10 Replies 5 Participants Last post by  dany1000
Hi. I recently purchased this gsxr 600 k3 with the FI light on and a C28 error code showing when in dealermode. When i opened up to see whats under the tank i found theres a problem with the STVA, which there should be according to the code. Theres also a beeping/squeeking sound. Ive been googling the problem, but without finding anything thats fully applicable to my problem.

I filmed the STV while starting up:

I grately appreciate any thoughts shared on the matter.
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I think this one or run by pulley
If so check it's tension, put into dealer and check the mark

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I think this one or run by pulley
If so check it's tension, put into dealer and check the mark

Sent from my Redmi Note 9 Pro using Tapatalk
Thanks for ur reply, but i dont understand what u mean. Could you try to reformulate what you're saying please? :)
The squealing you hear is the fuel pump. The service manual has testing procedures for the STVA. C28 tells you what system has the problem, not the specific component in the system. Based on the way it's moving, I think the secondary throttle position sensor is suspect. Sometimes they short internally and fool the ECM into thinking the STVA is moving erratically when in fact it's just bad data. The ECM just doesn't know the difference.

However, that STVA is a one off and was only ever used on the 2003 600. It's a bit of a goofy design compared to all of the other STVA designs.
The squealing you hear is the fuel pump. The service manual has testing procedures for the STVA. C28 tells you what system has the problem, not the specific component in the system. Based on the way it's moving, I think the secondary throttle position sensor is suspect. Sometimes they short internally and fool the ECM into thinking the STVA is moving erratically when in fact it's just bad data. The ECM just doesn't know the difference.

However, that STVA is a one off and was only ever used on the 2003 600. It's a bit of a goofy design compared to all of the other STVA designs.
Hey! thanks for the reply. I see. Any suggestions for what i should do with the problem? any point in buying a new STVA for example? what about removing the valves?
I dunno, may pull out the manual and do the diagnostic procedures?
Hey! thanks for the reply. I see. Any suggestions for what i should do with the problem? any point in buying a new STVA for example? what about removing the valves?
Yes remove the secondary butterflies. If I remember correctly they font sell parts separately. Choice is to get new or used throttle body. Removing the secondary butterflies can make a few more HP top end but may produce a small flat spot on the bottom end. If you have a tuner I suggest cleaning the fuel map up after removal.
I fixed a stva from the old ones by replacing the plastic gear from a exhaust servo unit

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^^^ Not a 2003 you didn't.
Think it was on 2002

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