I have GSXR TBs on ST170 manifold on my zetec. There is an induction whistle from 1/8 opening to about 3/8 open. Not present at idle and not present if I accelerate oh so gently. Not the alternator belt cos I removed it this evening and the noise was still there. No difference with or without trumpets or air box. Its driving me nuts and people turn in the street and look!
Cant find an induction leak. Had it all to bits today and refitted carefully but no change. Can't find an induction leak.
Help
Doesnt do it on overun if I close throttle at 5000rpm and slow when vacuum ought to be at max.

[Edited on 7/6/06 by Dusty]

Got any pictures of the setup? which GSXR TB's are they, 600 or 750/1000?

Not very good one.
Rescued attachment tbs2.jpg

Have you checked that the balance hoses from the vacuum ports on each TB are linked properly?

Also note that #4 TB has two vacuum ports, the "extra" one should be sealed off. I would leave the balance hoses connected but seal off the "T" that originally went to the IAP sensor if you don't need a vacuum hose to do something..

Olrowdy
[Building a GSXR1000 CMC7]

This is interesting as my GSXR750 TBs do exactly the same. I think it may be because of the steps I have in the inlet tract, connecting my TBs to a cut down original zetec manifold. TBs are 42mm, inlet then opens to 48mm for about 25mm length, then drops back down in diameter again.

I think the ST manifold gives some slight steps in the flow, I have heard of people reshaping the plastic with a dremel to smooth them out- it may be worth giving this a go.

In the long run I plan to go to a custom manifold, if this sorts the problem of the chirping I will be happy!

Neil

Mine do the same....

Sussed it today. I have had the air idle bypass screws closed and controlled idle on the ECU and a throttle stop. I cracked each idle bypass screw 3/4 of a turn and the whistle has gone. What a relief. They sound just like twin fortyfives without the whistle.

ps I did the radiusing and smoothing of steps yesterday while I was trying to get rid of the noise but it made no difference.

[Edited on 8/6/06 by Dusty]

Hmmm, mine don't have air bleeds, so looks like I'm stuck with the whistling for the time being!



Neil

The air bleeds are under the butterflys. I've made an attempt at a cross section of a TB to try and show the arrangement.
Rescued attachment bleed.jpg

Nope, not there on post 2000 GSXR750s...



Neil

Got my '01 GSXR1000 bodies installed and running on my tin top (mk2 golf 16v) today, they're whistling too, and I also don't have any bypass screws. I suppose I might be able to sort it by drilling a tiny hole or two in the butterflies, but I don't really feel like doing that quite yet, will see how I get on with it

The noise at all other times is fannytastic though, sounds like the world is ending. The most obvious solution for the kamikaze out there would be to never bother with light throttle of course

Out doing first mapping runs yesterday and I have this noise too. Don't think I have an air bleed on my TBs but I'll have a look when I get outside.

Anyone successfully quieten it on TBs without the airbleed?

Chris

I don't have it on mine. No bleed screws but no whistle.

It could just be that I don't drive on light throttle though

I have blended my inlet manifold to ensure no steps thoughtout the inlet tract so this may be it.
Without hearing it is hard to tell but does it sound like air or could it be the fuel pressure regualtor

I don't have an idle valve (yet) and I know these are a common problem for creating noise.

Mine still whistle, even after a change last month to a custom manifold. I've actually got used to it now and don't think about it any more. I assume they don't do it on the bike, but wonder if the (now removed) secondary butterflies change the flow characteristics slightly and stop the whistling...? Who knows...