Kawasaki Ninja ZX Forum banner
1 - 14 of 14 Posts

·
Registered
Joined
·
96 Posts
Discussion Starter · #1 · (Edited)
Hello Everyone,

Not to long ago I did the needle lift mod on my carbs. Everything is ok, but I think I'm burning to much fuel. I'm only getting about 28 miles to the gallon as of last week. When I did the lift I set my idle air screws out 2.5 turns. I was getting about 27 at that point. I then turned them down to 2 turns and gained a mile per gallon. My thing is, can I turn them down any further but get the benefits of the mod. On top of that, I don't want to lean it out so much that I burn a valve. I smell to much gas also...

To add, what where the idle screws set at from the factory? I remember it was about 1.5 turns out? Will the center be different being that the jets are different?
 

·
Registered
Joined
·
33 Posts
I am having a similar prob. No wheels yet, so I can't say how the actual fuel mileage is, but with my pilot screws at 2 turns on my 90' I am also smelling way too much gas at exhaust and the carbs drain my temporary fuel tank in minutes. I have adjustable needles with c-clip in third slot, and no shims under. (Sorry Claude, I won't be buying yours, the carb I got from ebay already had the Ti needles!) Clymer manual won't specify how many turns is factory. (Says "preset at factory")

My old/bad carb was set at 3.5 turns, and the new one from ebay from a 92' model was set at 1.5 (Not that this means anything! :))

I also have light backfiring throughout the entire range, not sure if it's related to the carb issue or not though.

Anyone running less than two turns on their pilot?
 

·
Registered
Joined
·
34 Posts
Pilot screws

Haynes manual says; UK models 2 turns out, US models Preset.
When spec says preset,this should be regarded as fixed,and not altered by other than experienced mechanics w proper diagnostic equipment.
If ever changing the settins,one should first screw them in until they seat lightly,counting the turns as we do so.

Probably not helping you a lot,but maybe other that reads it.

Good luck.:smile
 

·
Registered
Joined
·
2,173 Posts
... Not to long ago I did the needle lift mod on my carbs. Everything is ok, but I think I'm burning to much fuel. I'm only getting about 28 miles to the gallon as of last week. When I did the lift I set my idle air screws out 2.5 turns. I was getting about 27 at that point. I then turned them down to 2 turns and gained a mile per gallon. My thing is, can I turn them down any further but get the benefits of the mod. On top of that, I don't want to lean it out so much that I burn a valve. I smell to much gas also...

To add, what where the idle screws set at from the factory? I remember it was about 1.5 turns out? Will the center be different being that the jets are different?
It's always hard to give advice about carb tuning as each bike can vary. I will just add some comments, hoping it can help. First, I think that getting 28 MPG on a ZX-11 involve one (or two) things out of two possibilities: 1- You're riding very and extremely hard, 2- There's something wrong with your bike. I am an old fart riding sedately and I always get about 40 MPG Imp. My air screws are at 2½ and I have adjustable needles at notch #3. Mine is a 1990 C model though.
I don't say it is your case but a common mistake is using a jet kit and installing the largest MJ that comes with it, assuming it will run better under the "bigger is better" way of thinking school.

Almost every ZX11 rider I know adjusted their air screws between 2½ and 3 turns and shimmed their (OEM) needles to improve the surge problem around 3500~4500 RPM. Maybe one MPG got lost but the benefit were largely offsetting. And all of them regularly got a strict minimum of 35 MPG and some, 43~45 !

In short, I think you're carbs could be too rich but possibly in the MJ. Do you have stock jetting?
 

·
Registered
Joined
·
2,173 Posts
Oh and personally, I would not go under 2 turns at the air screws. Anyway, the aforementionned 3500~4500 RPM surge will possibly show its ugly head before getting a 2 turns. If your screws are at 2 turns and you do not have this surge, my humble opinion is that you possibly are way too rich in one of the next steps (needles, MJ).

Another question: do you know how "high" your floats are adjusted at?
 

·
Registered
Joined
·
2,173 Posts
...I have adjustable needles with c-clip in third slot, and no shims under. Clymer manual won't specify how many turns is factory. (Says "preset at factory")
If you want a position about equal to OEM needles, you should ajust them in second slot (counting from top). No need to shim them; they are adjustables. Shimming is only for OEM needles or if you really want to get "half positions" on adjustable ones...

...My old/bad carb was set at 3.5 turns, and the new one from ebay from a 92' model was set at 1.5 (Not that this means anything!
My humble opinion: I think 3½ turns is way too much and 1½ way not enough. Best is 2½~3 turns. If you need more than 3, you're possibly to lean on the needles.

...I also have light backfiring throughout the entire range, not sure if it's related to the carb issue or not though...
Like you said, maybe not carb related. But it could be if too lean. Depends what your AS are adjusted at.

...Anyone running less than two turns on their pilot?
I think I already replied to this somewhere above...

...(Sorry Claude, I won't be buying yours, the carb I got from ebay already had the Ti needles!)...
Too bad for you; my needles are way better than yours...:lol
 

·
Registered
Joined
·
33 Posts
Thanks Claude! I appreciate the knowledge. I do have another question for your guru-ness though. The jets that were in the carb were 148's as I wrote you before, but they were longer than the stock 155's I have (Which are in the carb now). What do the dynojet jets look like? I am curious what kind of a setup I am looking at. I have a suspicion that the slides have been drilled. Will this affect the way the carb behaves if the slides are drilled, but the stock MJs are installed and needle is in slot 2 or 3? Is there always a hole in the top of the slide, and it is just enlarged with the jet kit? If there is an existing hole what is the stock hole size? (I have measuring pins available to check the hole size) Thanks again! Your knowledge is admirable! (And I'm sure your needles are better than mine! :))
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #8 ·
Hey Guys,
This bike was stock when purchased not to long ago. The bike had just over 4k miles on it. I'm the only one that's actually done anything to it as far as any mods. That being said, it's had the needle lift and a K&N air filter. No jets have been changed nor has anything else. I had to drill the little cap off at the idle air screws myself to adjust. I guess I should've wrote down the "preset" settings but wasn't worried about that at the time. It was 4 different figures anyway from what I remember but not 100% sure.The bike is running rich for sure. As far as the float setting not sure there either but it should be at the stock setting....I guess ths is going to be trial and error thing from reading the pevious post...
 

·
Registered
Joined
·
33 Posts
As Claude said it could be fuel level jlgwinn. Stock is 13mm +or- 2mm. The higher the level, the less vacuum it takes to suck the fuel out of the bowl causing a richer mixture. I just remembered I set mine at 15mm. Could be too high....


Edit: On second thought if the floats are measured with valves beginning to close at 15mm then there is less fuel in the bowl than if the height was 13mm. Sorry for the misinformation!
 

·
Registered
Joined
·
33 Posts
I only remember one hole in the slides, so hopefully it is still stock. I guess the hole provides more vacuum to lift the slides quicker, which is great as long as you can supply the greater amount of air/fuel. I am not sure what the effect would be if all else is stock.

My jets are Keihin 155s which are stock for the 90'. The ones that were in the carb I bought on ebay, say only "148", with no other markings, but extend (roughly from memory) about .1" more than my stock jets into the bowl. The seller claimed the carbs were from a 92' (stock for 92' is not 148)
Are Dynojet jets marked with a DJ? How about Factory pro? Just curious!
 

·
Registered
Joined
·
33 Posts
Stock jets are stamped on the side, the long ones are stamped on the face.
The head of the jet is equal to or more than double the length of head of the stock jet. Yeah, they are a lot longer, which is why I am so curious...
 

·
Registered
Joined
·
2,173 Posts
...Is there always a hole in the top of the slide, and it is just enlarged with the jet kit? If there is an existing hole what is the stock hole size? (I have measuring pins available to check the hole size)...
Here are the links for Dynojet's instructions. For D models, you drill an additional hole in the slides. But for C model, you enlarge the actual one (with the supplied #32 drill bit).

I already chatted a bit with Marc Salvisburg (owner of Factory Pro) and he told me the hole in the slide could create more problem than it can solve. I believe him so I never drilled any slide and I always prefered Factory Pro's jet kit as they use the same MJ as Keihin. I think Dynojet's different numbers are way too confusing (but that's just me).

90~93 C : http://www.dynojet.com/pdf/2143.pdf

93~97 D : http://www.dynojet.com/pdf/2151HA.pdf

98~01 D : http://www.dynojet.com/pdf/2190.pdf
 

·
Registered
Joined
·
2,173 Posts
...Which begs the question, what changed between the D2 and D3?...
My bet goes for reduced emission standards. But, as usual, I could be wrong...


...And how the f*** do I measure 1&5/8 turns on my D2. Pah!
Geez Pacman, how can you ask such a thing. It's right in the middle between between 1&9/16 and 1&11/16 turn...:lol
 
1 - 14 of 14 Posts
Top