Exhaust flappy widget failure

[Roymondo]

The strange butterfly valve widget in my bike's exhaust system seized just before Christmas. Quick phone call to dealer and booked in for warranty replacement today.

Currently sitting in Wollaston's cafe (thank goodness for free coffee to be told that the new valve has been fitted. Only now there appears to be a problem with the actuator/motor as well. Ho, hum...

What does the thing do anyway? Can't say I noticed much difference when it wasn't working (other than a teeny bit more pop & crackle on the over-run).

 

[snerkler]

I thought it was only there to close off at a specific rpm to please the euro regs guys, so most of the time is redundant I'm sure someone will be along soon to elaborate.

 

[Roymondo]

Well, with a new motor and valve fitted it certainly does sound different. Not as "crackly" at low revs. Can't say I've noticed any difference in the way it goes though. I think it had been out of action for some time...

On the plus side, the dealer also replaced the blown headlamp bulb that I was going to deal with when I got home

 

[scrubs]

I would imagine it works the same as a power valve on a crosser..for instance on my crm250AR if I disable the electronically controlled
PV and leave fully open - I lose some low down torque then it snaps into life half way through the rev range rather than a smoother
more gradual power delivery.

I know there has been some debate that it was only put there for emission purposes, and the whole low end torque thing is nonsense and since
I have not removed mine yet can not confirm, but I can say having done this on other bikes it definitely effected low range torque, so would be surprised if the 1200 acted any different.

 

[Schtum]

I would imagine it works the same as a power valve on a crosser..for instance on my crm250AR if I disable the electronically controlled
PV and leave fully open - I lose some low down torque then it snaps into life half way through the rev range rather than a smoother
more gradual power delivery.

I know there has been some debate that it was only put there for emission purposes, and the whole low end torque thing is nonsense and since
I have not removed mine yet can not confirm, but I can say having done this on other bikes it definitely effected low range torque, so would be surprised if the 1200 acted any different.

Agreed - I suspect that at least part of the reason that the twin cam engine has more bottom end grunt than the previous 1200 is because the valve in the pipe helps to keep exhaust gas speed up at low revs which also aids with cylinder filling because of inlet / exhaust valve overlap.

 

[bod]

Mine was replaced last month also, can't tell the difference!

1 and a half winters is just not good enough!