Power Valve

[John Armstrong]

Does your bike have one? The easy way to check is look at the end of the OEM exhaust can. If it's black it has one, if it's silver it doesn't.

The "valve" is at the lower end of the chrome cover ie next to the pillion foot peg. It almost completely hides under the cover and is about an inch in length. I've no photo's and found out about it from Mitch at Williams when I was getting the first service done. There isn't any obvious reason on why there is / isn't one. For example I've a Nov 05 delivered bike with one and saw a 05 yellow one in Hawes today which hadn't.

And I've no idea what effect it has, but mine has a nice thoatiness to the tone, but only when under load, ie not sitting still.

BTW Yellow 12GS are so common.

 

[Mr K]

Power valve?
That's 2-stroke gubbins.........Sheesh!

:drackula

 

[John Armstrong]

Power valve?
That's 2-stroke gubbins.........Sheesh!

Ah so you'll have a common yellow one without the valve?

 

[JJ Crafford]

Ja, my 04 bike has what you refer to as the 'valve'. does have a deeper sound than some other gs's i've ridden with, but I wasn't aware of this difference. what does this valve do?

 

[John Armstrong]

JJ.

Haven't a clue at the actual benefits, but as you say it does seem to make a throatier sound. I guess it's playing with the resonances that naturally occur in exhausts. Not a clue if you can retrofit one to a valve-less can either. But then I don't have to worry about that.

Didn't Micron have something like this a while back?

 

[(RIP) Kaister]

2005 build models only.

Again - only 15 yrs behind Yamaha.

F1 teams been using them for 6 yrs now

http://www.motorcycle-usa.com/Article_Page.aspx?ArticleID=770&Page=2

 

[John Armstrong]

Looking at it from the front. The lettering is:

SAM 294 04

212793 H 23086

 

[John Armstrong]

And from the side:

 

[John Armstrong]

And the black end piece:

 

[KAYCEE]

2005 build models only.

My 2004 (sept) model has this "valve"

 

[Mr K]

Yeah, well mine has that, but it's not a "power valve" in the sense we've come t know them i.e : YPVS, EXUP et al.............

It's just a lump of tech gubbins...go on, call me a fibber!

 

[Mr K]

...........and mines a Nov 04.........so where does the theory go and what is the question anyway?...I t looks like an evap-filter rather than anything to do with "power" anyway....

 

[Panzer Patrol]

That thingy is perhaps best described as a pressure release valve. At low rpm, exhaust back pressure plays an important part in helping to maintain the oodles of torque these engines have. However, when one wants to hop on a bit, back pressure can be restrictive. So the valve opens under increased exhaust pressure and allows the silencer to be less restrictive. Hence the whisper quite mode when tootling along, and the rather nice chortle when one is flogging the wick out of the thing. I dont know, but it is possible that the exhaust only uses one of the outlet pipes in potter mode, (nice and quiet) and both outlet pipes when the valve opens (nice noise mode). I cant find anyone to stick their hand over the end to find out I can certainly hear a kind of turbo type whittering noise when I am changing gear in rev limiter thrash mode. So something is happening down there And since a rather spirited ride on Sunday I have also found that its bloody hard to keep the front wheel on the ground in third, sometimes in fourth and impossible in second. Damn, I love this bike

 

[TheJoker]

Panzer, I think you're on the right lines, but I suspect (i.e speculations), it's got more to do with noise than outright power.
Thumpers are extremely difficult to silence, and big twins come a close second - where an inline four is quite simple to silence.

I do guess that the gubbin is designed to, thanks to exhaust pressure, either open up a more direct pipe out to the open, and thus releasing more power, more noise, and bigger grin...

OR, the gubbin is flexible, which means that it'll dampen the sudden blows coming from the cylinders, kind of like a flexible expansion chamber - however due to heat I suspect that option 1 above is more likely.

Anyone want to put a hacksaw to their OEM pipe and have a look for us, purely research...

 

[swebb]

I've read with interest the many speculations regarding this so-called "valve"

If indeed it's to do with silencing.... why don't ALL models have it? And what do those without use in it's place?

Hmmmmm chat with dealer looming me thinks....... unless somebody beats me to it?

 

[toucan]

what about supertrapp?

not the band, the exhaust.
spring loaded discs on the back of the exhaust limit back presssure. sounds like bmw are using a similar theory.

 

[John Armstrong]

Maybe it's a way around the noise regulations as aren't they at a constant throttle setting?

BTW I've re-read my first post and I don't have a bike that will be produced in 8 months! Does anyones 05 registered bikes have one, as mine is an 05 bike as I've the small toolkit?

 

[Tobers]

Mine's got what looks like a valve at the lower rear of the engine which is connected to a braided steel tube.

This tube goes up around the rear of the engine and under the tank. It then leads up the handlebars to a read switch. This in turn is connected to another braided steel tube which goes back down under the tank to a cannister under the rear seat.

I looked at this more closely and found that it was labelled N2O, which I thought was a bit of a laugh.

Anyway, its a 2004 build and it must explain why the yellow ones are fastest

 

[TheJoker]

Mine's got what looks like a valve at the lower rear of the engine which is connected to a braided steel tube.

This tube goes up around the rear of the engine and under the tank. It then leads up the handlebars to a read switch. This in turn is connected to another braided steel tube which goes back down under the tank to a cannister under the rear seat.

I looked at this more closely and found that it was labelled N2O, which I thought was a bit of a laugh.

Anyway, its a 2004 build and it must explain why the yellow ones are fastest

Sounds to me like one of those tubes are leaking, Tobers go out n get some fresh air...

... AND IT'S NOT FUNNY!!!!

 

[Rich]

I'm astounded at the lack of technical knowledge here

Chaps, its the horn.