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the exhaust butterfly valve, originally poineered by yamaha as the exup valve, depending on which model, moves with the rpm band. rests at about 15% open at idle and is like 90% open at the point where the secondary injectory spray more fuel than the primaries do. hope that helps.
 

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Discussion Starter #23
You got any results yet RJ?
I'll check it out today and report back, Cav. It's 21° F at the moment, headed up to around 40 later today. I need to take the bike out and top up the tank. Once I've got it warmed up I'll check what RPM the valve position changes at.

That's still a guess, as we still don't know if the controls for the valve have any input from gear selection, wheel speed, etc.,etc. Too many OEM ECUs are programmed to give different performance in first and second, and at max speed in top gear.
 

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Discussion Starter #24
By touch, the cables tell me the valve moves at 4K RPM, and again at 8K. I didn't rap it out far enough to see if it moves again anywhere else....

Next time I get to ride it to work, I'll have one of the kids that works with me assist, and I'll check it all the way to red line.
 

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Hi guys,

Apologies for resurrecting a very old thread but it is relevant to my question and video.

In brief, my 2005 had a Scorpion can and the servo removed but was failing noise tests at my local circuit. The only can with a specification to get below the required 101dBA at 7000rpm is the OEM can. Hence a £200 mini project to fit a used OEM can along with servo, cables, new tail tidy, number plate etc. Fun but irritating at the same time.

Anyway, I've fitted the exhaust cables as per the service guide but I'm unsure whether the valve opening and closing is working at the right point. I know I could just ditch the servo and keep the quieter can but with noise testing being my main consideration I'd like to try to keep it until I can assess the impact on top end on the track.

It seems to me that the valve is part open at idle. Approaching 5000rpm the valve then closes before opening fully by 10000rpm. You can see and hear this change on my video at

I'm hoping someone can confirm this operation is normal. If I've messed up the cable attachment at the servo pulley or fitted the cables incorrectly on the valve pulley then the bike will run like crap with random valve openings.

If no-one know, maybe this video will be useful in the future for someone else with questions about when the valve opens and closes....
 

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Discussion Starter #26
It's normal.... fully open above and below that mid point. The cable routing is straight forward, they could have run a single wire to pull the valve closed, as the spring in the assembly at the pipe constantly tries to pull it to the open position. the two wire 'push-pull' setup is a belts and suspenders solution.
 
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