littleman
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| posted on 15/9/10 at 07:23 AM |
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ZX9r stuttering at 6k rpm
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.
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mistergrumpy
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| posted on 15/9/10 at 08:46 AM |
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He's the professonal I suppose. I take it you have got a dynojet kit fitted and the needle heights adjusted?
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Wadders
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| posted on 15/9/10 at 09:22 AM |
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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
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littleman
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| posted on 15/9/10 at 09:29 AM |
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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.
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mistergrumpy
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| posted on 15/9/10 at 09:43 AM |
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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.
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Wadders
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| posted on 15/9/10 at 09:56 AM |
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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.
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littleman
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| posted on 15/9/10 at 10:10 AM |
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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.
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Wadders
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| posted on 15/9/10 at 10:42 AM |
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Raising the needles richens the mixture, lowering them weakens the mixture.
Al
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littleman
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| posted on 15/9/10 at 10:47 AM |
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So if its stuttering do i need to move up or down? suppose it could be either really!
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Wadders
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| posted on 15/9/10 at 11:03 AM |
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Assuming they are not already on the top groove, try leaning it out a bit by dropping the needles a notch.
Al
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mistergrumpy
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| posted on 15/9/10 at 12:40 PM |
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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. If it was good enough for Mr Kawasaki then
it's alright by me.
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matt_gsxr
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| posted on 15/9/10 at 12:50 PM |
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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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whitestu
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| posted on 15/9/10 at 02:02 PM |
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quote:
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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littleman
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| posted on 15/9/10 at 02:56 PM |
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quote:
Originally posted by matt_gsxr
Have you considered going back to the stock airbox?
Matt
The standard air box isnt really much of an option as the bonnet has a cut-out for the foam filter to stick through.
This issue is a pity as it is really stopping me enjoying the car as much as i would like to.
quote:
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.
He tried a harder spring and a softer spring and we took the one with the best result, which i think was the softer one. Definitely imporved it!
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tomgregory2000
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| posted on 15/9/10 at 04:05 PM |
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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?
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Wadders
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| posted on 15/9/10 at 05:24 PM |
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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
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PaulYDP
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| posted on 16/9/10 at 02:12 PM |
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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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JoelP
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| posted on 16/9/10 at 08:11 PM |
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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.
Beware! Bourettes is binfectious.
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littleman
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| posted on 17/9/10 at 08:21 AM |
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quote:
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]
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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mackei23b
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| posted on 20/9/10 at 04:07 PM |
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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
quote:
Originally posted by littleman
quote:
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]
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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littleman
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| posted on 25/9/10 at 02:02 PM |
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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?
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