Need help! carbonation problem?

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Awacs
Posts: 21
Joined: Mon Nov 21, 2011 2:18 am
My Bike: ZXR 400 L4

Need help! carbonation problem?

Post by Awacs »

Hello friends
I am a proud ZXR 400 owner from Spain …. in Great Britian this bike is common, but in Spain its very rare, it wasn't sold here (sorry my english)
I say this to explain I don't have any spanish forum where to ask about this bike…. all the replacements and spares I need I always buy it on ebay.co.uk

So… I have a problem with the throttle-cabr of my ZXR 400
It appears around las summer (I have this bike 1 year ago, bit more, and it always have ran perfectly, without carb or throttle problems)
the problem is: at high rpm (between 10.000 and 14.000, and only between then) when I hold throttle (reaching a curve or just turning and don't want to continue accelerating) I hold the throttle and keep the engine rpm high (to be on the power band) and when I continue "throttling" (I don't know how to say in english) there is like a second o half second of retardation, where the bike/engine doesn't accelerate, and then, it enters the power past that second and continues accelerating perfectly, as anything happened.
The bike runs sweet and perfectly, and has all the power, and runs in down speeds and rpm, to the highest rpm,,,, always good …. but when I gear down, on the power band (10->14k rpm) or just, for example; I am in second gear, at 12.000rpm aproaching a curve, and then, I stop twisting the throttle, and I hold in intermediate position (I don't close at all) and I hold there, to have enough power to turn, and when I am in the middle of the curve or getting away, I twist the throttle to the end to accelerate,, and there, there is when I have this problem.
Is like a big retardation of "power" entering … or something like that

I installed a DynoJet kit (stage 1) ,,, the bike runs very good, even I think it has more power,,, but this problems continues.. even it got worst :(
I take the needle up one position, and the problem gets smooth, but on the rest of the rpm, the bike it doesn't run as good as before,,, it has like a "rich feeling" on the throttle response

My mechanichs doesnt know how to fix it, ,, he says the bike has an air entry somewhere ,, but doesn't know neither where and how …
I am getting mad, becuse along the winter I didn't care, but know on summer I am running on track, and I want to solve this urgently …

Sorry for my english, if something is not clear, please notify, I will try to write it better with the translate google.

Thank you very much
Awacs
Posts: 21
Joined: Mon Nov 21, 2011 2:18 am
My Bike: ZXR 400 L4

Re: Need help! carburation problem?

Post by Awacs »

ups, in the title I make mistake, I mean CARBURATION, no carbonation … don't know how to edit the first message and title,,, sorryp :S
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RedexRobB
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Joined: Fri Aug 30, 2002 7:37 pm
My Bike: ZXR400L3
Location: Ipswich, Suffolk

Re: Need help! carbonation problem?

Post by RedexRobB »

Your bike has a hard life by the sound of it. Lol

If it runs well otherwise, then its probably just a flat spot. You can alter the fuelling, (my guess would be you need larger main jets?), but your probably best getting it on a dyno to see whats going on with the fuelling.
Awacs
Posts: 21
Joined: Mon Nov 21, 2011 2:18 am
My Bike: ZXR 400 L4

Re: Need help! carbonation problem?

Post by Awacs »

yeah,, that would be great, to use a dyno,,, but here, all the dynos, sorry, all the garages who have dynos, dont't want carburation bikes … they see them as old and,,,, :S

Main jet,,, I have the DynoJet Stage 1 Main Jets "96" … and I have anothers "92" … do I have to look for/buy anothers biggers?

thanks a lot!
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banner001
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Joined: Sat Sep 24, 2011 3:27 pm
My Bike: ZXR400 L4
Location: Nuneaton

Re: Need help! carbonation problem?

Post by banner001 »

hi there, easiest way is to put bigger (i.e. 100's or 105's) main jets and see if that helps it, if not, try smaller ones (i.e. 92's in all 4 cylinders).

if you have 96's in some cylinders, and 92's in others there are 2 reasons for this:-
1. people put larger main jets in the central 2 cylinders as the extra fuel helps to cool the cylinders

or

2. people put smaller jets in the middle 2 cylinders as the gas is hotter there and less dense so you dont want to use as much petrol in order to keep the bike running properly.

i dont know what the general consensus for the zxr is though if you want to go for mixed jets.

in my bike i have a freeflowing exhaust on copy-headers, a k&n filter in the airbox with the snorkel removed and the silencer cover in place, i run 3 shims under my stock N77S needles to raise them by ~1.5mm and i run 105 main jets with the pilot air screws set to 2 and 3/4 turns from fully screwed in.
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
Awacs
Posts: 21
Joined: Mon Nov 21, 2011 2:18 am
My Bike: ZXR 400 L4

Re: Need help! carbonation problem?

Post by Awacs »

hey banner, thanks,,, but I think I didn't express well, ,, I mean I have anthers manin jet, but they are at home, in a box where I keep all the pieces of the bike …. the bike is now runing with 96 in all the cylinders
6K1RKYJ9
Posts: 17
Joined: Sun Jul 01, 2012 10:31 pm
My Bike: zxr 400 l4, 94
Location: Belfast, NI

Re: Need help! carbonation problem?

Post by 6K1RKYJ9 »

banner001 wrote:hi there, easiest way is to put bigger (i.e. 100's or 105's) main jets and see if that helps it, if not, try smaller ones (i.e. 92's in all 4 cylinders).

if you have 96's in some cylinders, and 92's in others there are 2 reasons for this:-
1. people put larger main jets in the central 2 cylinders as the extra fuel helps to cool the cylinders

or

2. people put smaller jets in the middle 2 cylinders as the gas is hotter there and less dense so you don't want to use as much petrol in order to keep the bike running properly.

Hi could you elaborate on this please as its confused me a bit :smt009 . I've 95 standards in mine at the minuet but I'm changing them up as I've just put on a k&n. I'm not too sure whether to put bigger in the middle or outer 2??
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banner001
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Joined: Sat Sep 24, 2011 3:27 pm
My Bike: ZXR400 L4
Location: Nuneaton

Re: Need help! carbonation problem?

Post by banner001 »

6K1RKYJ9 wrote:
banner001 wrote:hi there, easiest way is to put bigger (i.e. 100's or 105's) main jets and see if that helps it, if not, try smaller ones (i.e. 92's in all 4 cylinders).

if you have 96's in some cylinders, and 92's in others there are 2 reasons for this:-
1. people put larger main jets in the central 2 cylinders as the extra fuel helps to cool the cylinders

or

2. people put smaller jets in the middle 2 cylinders as the gas is hotter there and less dense so you don't want to use as much petrol in order to keep the bike running properly.

Hi could you elaborate on this please as its confused me a bit :smt009 . I've 95 standards in mine at the minuet but I'm changing them up as I've just put on a k&n. I'm not too sure whether to put bigger in the middle or outer 2??
i cant make it any simpler, i provided a pretty good explanation, generally, just go for the same jets across all 4 cylinders, however the middle cylinders always run hotter than the outer two, so IF you think this is causing you a problem there are 2 ways to deal with it and you need to see which setup works best for you IF you need it.

you can run a bigger size of main to add extra fuel which overly richens the mix and the extra fuel helps to cool the cylinders (this is the prefered option - always better to be rich than lean in a road bike), or you can drop a size in the middle two cylinders to bring the air:fuel ratio back to what it should be - hot air is less dense so you get slightly less air in the middle two cylinders, which means you need slightly less fuel to get the mix correct.

stick a single size of jets in, go for a blast, rinse and repeat, then stick it on a dyno and see how its fuelling, tweak the fuelling based on the dyno results, go for a ride then stick it back on the dyno and see what your changes have done.
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
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