Z1OwnersClub GB

Hi there folks, i am having trouble with my KZ900 A4, poor running, done almost everything imaginable to cure it, last but not least, the carbs were stripped, sonically cleaned, rebuilt, set, tuned, not much better, so my conclusion now is that there may have been a four into one on it at one time, and the owner may have changed the jets etc to suit, i also suspect that the person i bought it from added a new four into four replica set of pipes and not fitted the standard jets etc, do any of you Kawasaki owner know the size of all the jets, needles and weight of the floats, i am seeing so many differences in sizes i am confused.
Does anyone have a list of the correct sizes of all the carburetor components.

I would be grateful to hear from anyone on this.

Blueboy1959

std a4 jetting as follows :

main 115
pilot 17.5
needle 5DL31-3
cutaway 1.5
fuel level 3mm
float height 22mm


Check your choke seals as well

What are your airscrews set to? Most references I've seen say 1 & 1/2 out from lightly seated but every a4 I've set up with colour tune burns the best colour at 3/4 out from lightly seated. Assuming stock jetting etc.
1 & 1/2 out means they are very lean at low revs. What plug colour do you have?

Blueboy1959 wrote:Hi there folks, i am having trouble with my KZ900 A4, poor running, done almost everything imaginable to cure it, last but not least, the carbs were stripped, sonically cleaned, rebuilt, set, tuned, not much better, so my conclusion now is that there may have been a four into one on it at one time, and the owner may have changed the jets etc to suit, i also suspect that the person i bought it from added a new four into four replica set of pipes and not fitted the standard jets etc, do any of you Kawasaki owner know the size of all the jets, needles and weight of the floats, i am seeing so many differences in sizes i am confused.
Does anyone have a list of the correct sizes of all the carburetor components.
I would be grateful to hear from anyone on this.
Blueboy1959

Don't assume bad running is carbs.
Check the jets sizes etc as per the above info.
Might also help if you described what bad running you are seeing.

You need to have checked the following and corrected issues:
Compression
Valve clearances
Cam timing
ignition timing and correct advancement
points cap and condensers (if fitted)
Coil voltage (bare minimum 11v, but ideally 11.5v)
Plugs
Coils
Reg/rec and stator output
Battery voltage
Choke plunger seats
Correct air filter
Airbox lid fitting and sealing correctly
Air box to carb and carb to head rubbers leaking and passing air

I think first you need to make sure valve settings and other basic settings are correct, then make sure what model carbs you have, then we can give you some base settings for it, are you running an original airbox?

warren3200gt wrote:What are your airscrews set to? Most references I've seen say 1 & 1/2 out from lightly seated but every a4 I've set up with colour tune burns the best colour at 3/4 out from lightly seated. Assuming stock jetting etc.
1 & 1/2 out means they are very lean at low revs. What plug colour do you have?

Hi mate, sorry for the late reply, until now they have been sooted and black, i dropped down to B7ES plugs, it helps with firing up and seems to run a bit better,

kev edwards wrote:I think first you need to make sure valve settings and other basic settings are correct, then make sure what model carbs you have, then we can give you some base settings for it, are you running an original airbox?

Sorry for the late reply, yeh standard airbox, 26mm Mikuni's, all valve clearances done, carbs sonically cleaned, rebuilt, vacuum set, new coils, new electronic ignition, just half way through fitting a new regulator/rectifier, my biggest fault may be i have a GSX1400 and always comparing them, well, no comparison really although i love them both. A lot of head scratching going on here.

chrisu wrote:std a4 jetting as follows :

main 115
pilot 17.5
needle 5DL31-3
cutaway 1.5
fuel level 3mm
float height 22mm


Check your choke seals as well

\much appreciated, thank you very much.

Ultim8pc wrote:

Blueboy1959 wrote:Hi there folks, i am having trouble with my KZ900 A4, poor running, done almost everything imaginable to cure it, last but not least, the carbs were stripped, sonically cleaned, rebuilt, set, tuned, not much better, so my conclusion now is that there may have been a four into one on it at one time, and the owner may have changed the jets etc to suit, i also suspect that the person i bought it from added a new four into four replica set of pipes and not fitted the standard jets etc, do any of you Kawasaki owner know the size of all the jets, needles and weight of the floats, i am seeing so many differences in sizes i am confused.
Does anyone have a list of the correct sizes of all the carburetor components.
I would be grateful to hear from anyone on this.
Blueboy1959

Don't assume bad running is carbs.
Check the jets sizes etc as per the above info.
Might also help if you described what bad running you are seeing.

You need to have checked the following and corrected issues:
Compression
Valve clearances
Cam timing
ignition timing and correct advancement
points cap and condensers (if fitted)
Coil voltage (bare minimum 11v, but ideally 11.5v)
Plugs
Coils
Reg/rec and stator output
Battery voltage
Choke plunger seats
Correct air filter
Airbox lid fitting and sealing correctly
Air box to carb and carb to head rubbers leaking and passing air

Wow, that is a long list of possible issues, but thank you for all the pointers, i have some of them complete already, but will now eliminate some more, thank you.

Look in the mouth of the carbs.
If you see the brass jets (highlighted in white) as in the attached pic and are running an airbox they must be removed.
This would explain the sooted plugs.

just a random thought or 2.
Could 1 of the cams be 1 tooth out ?- you'd need to remove the cam cover and the points cover to check everything lines up.
if the carbs have been fully stripped and cleaned down to the last nut and bolt- could the slides have been fitted onto their lifters back to front? ie with the cutaway facing the wrong way( I'm unsure if this is possible on a Zed but Ive done it before with 1 other bike)

as regards cam timing , the factory diagram is slightly difficult to read- with the engine set to TDC, the front marker on the exhaust cam points to a pin on the cam chain. This is pin ZERO not pin ONE so when counting to pin 27 or whatever it is on the intake cam, it is possible to get it wrong.( voice of experience again)

Been mulling this over. Good running at idle, good running when revving harder - problem is in the transition. Would weak advance/ retard springs lead to over advanced timing as engine revs begin to pick up, then as revs increase further , the timing becomes correct again?
I'm trying it on my bike today to see if it helps my z900

Good news!!
I pulled the advance unit springs out of a spare Z1R unit I had and swopped them over for the springs I had in the 900's advance retard unit - 1 was more stretched than the other.
Today went the same run as yesterday.
Lovely low throttle manners. no snatchy pickup out of corners, much smoother behaviour in roundabouts leading to more confident cornering. 95+% improvement from the behaviour of before. NOW A PLEASURE NOT A PAIN. A bit of air screw fiddling might improve the last bit .
So I agree with an earlier post- "carb/ fuelling problems" can be ignition based and vice versa.
Hope this gives some pointers

gray wrote:Good news!!
I pulled the advance unit springs out of a spare Z1R unit I had and swopped them over for the springs I had in the 900's advance retard unit - 1 was more stretched than the other.
Today went the same run as yesterday.
Lovely low throttle manners. no snatchy pickup out of corners, much smoother behaviour in roundabouts leading to more confident cornering. 95+% improvement from the behaviour of before. NOW A PLEASURE NOT A PAIN. A bit of air screw fiddling might improve the last bit .
So I agree with an earlier post- "carb/ fuelling problems" can be ignition based and vice versa.
Hope this gives some pointers

Glad you got to the bottom of this.
Enjoy!