I recently had my Tiger B6 ZX9R tuned on a rolling road but the tuner was unable to get rid of this stutter at 6k rpm. It pulls like a train after then but its hard to get through the 6k rpm area.

The tuner said he was having trouble balancing intake and exhaust pressures at that point and suggested i change from the 4-1 mani to a 4-2-1 mani and this should sort it out. Just wanting some opinions on this before i go spending hundreds on a new mani.

He's the professonal I suppose. I take it you have got a dynojet kit fitted and the needle heights adjusted?

4-2-1 is supposed to give better midrange power, so if its got the right needles in i would have to guess he's right.
Only other thing i can think would be airbox design, what are you using?

Al

I think he said the carbs had a pro-jet kit fitted from the factory when they were new. To my knowledge he did not adjust the needle height though, only the spring rates and main jet diameter.

Induction-wise its got a pipercross foam sausage filter which peeks out of the bonnet.

Its the needle height that governs mid range and on the Dynojet had around 4 grooves on the non pointy end so that this slightly alters how much fuel enters the main carb.
Not sure what you're referring to with spring rates.

agree with mr grumpy, not heard of the pro-jet kit, but the main benefit of the dyno-jet kit is the grooved needles, which allow you to adjust the fuelling in the mid rev range.

Al.

I have a dynojet kit which is fitted to some spare carbs i have so i could just take the needles out of there i guess? I know exactly what you mean about the 4 grooves, so do i need to move the washer up or down? Or do i just need to experiment?

By spring rates i mean the tension of the springs, i think he put lower tension springs in so that the needles would react quicker when throttle is applied.

Raising the needles richens the mixture, lowering them weakens the mixture.

Al

So if its stuttering do i need to move up or down? suppose it could be either really!

Assuming they are not already on the top groove, try leaning it out a bit by dropping the needles a notch.

Al

I have to say and it could just be me but I've never heard of anyone altering the spring rates. If it was good enough for Mr Kawasaki then it's alright by me.

I don't know about zx9, but gsxr1100 are well known to be very difficult (read impossible) to set-up without the standard airbox. I guess you have a similar problem.

The problem occurs at that same point (between the first torque peak and the second).

Have you considered going back to the stock airbox?

Matt

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I have to say and it could just be me but I've never heard of anyone altering the spring rates.

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Originally posted by matt_gsxr
Have you considered going back to the stock airbox?

Matt

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I have to say and it could just be me but I've never heard of anyone altering the spring rates.

+1
I don't see how you could accurately do this anyway. Sounds like he's talking rubbish to me.

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Why dont you run it with the air box on and see if it makes any difference to the engine just as a temp measure, then that will tell you if that is the problem or not?

Maybe i was just lucky, especially as i made my own exhaust manifold (4-2-1) and put the pipes into the collectors in the wrong order. Doh!
Still runs sweet as a nut right through the rev range.
However it was set up by Jack at Holeshot on his rolling road, so the credit goes to him.

Al









]Originally posted by matt_gsxr
I don't know about zx9, but gsxr1100 are well known to be very difficult (read impossible) to set-up without the standard airbox. I guess you have a similar problem.

The problem occurs at that same point (between the first torque peak and the second).

Have you considered going back to the stock airbox?

Matt

I race a zx9r in a Tiger B6 with no airbox fitted on a 4-1 manifold and it runs perfectly. I have the dynojet kit fitted and it was also set up by holeshot racing on their rolling road!

[Edited on 16/9/10 by PaulYDP]

i had a zx9 with a sausage filter, i used standard jets drilled to 1.65mm, had no problems midrange, just a hesitation at low revs from over fueling i suppose. Surely the tuner should have had no trouble with such a common engine? Theres thousands in kitcars.

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Originally posted by PaulYDP
I race a zx9r in a Tiger B6 with no airbox fitted on a 4-1 manifold and it runs perfectly. I have the dynojet kit fitted and it was also set up by holeshot racing on their rolling road!

[Edited on 16/9/10 by PaulYDP]

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I used the stock set up from Dynojet on my ZX9 with a sausage filter. You'll get the set up from www.dynojet.com

Cheers

Ian

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Originally posted by littleman

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Originally posted by PaulYDP
I race a zx9r in a Tiger B6 with no airbox fitted on a 4-1 manifold and it runs perfectly. I have the dynojet kit fitted and it was also set up by holeshot racing on their rolling road!

[Edited on 16/9/10 by PaulYDP]

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I have a dyno jet kit on another set of carbs so I will swap the needles over from them at the weekend, I don't suppose you know what groove your needles are set at do you?

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Changed the needles for the others from the dyno jet kit, they were set one notch richer. It struggled to idle and kept cutting out, the 6k stutter was still there too so changed them back. Any suggestions?