1980 z1 classic fouling plugs

Hello,

The mystery saga continues… sympton— plugs fouling wet, burning lots of fuel smoke and bogging when on the throttle. Yes this is still that original 1980 fuel injection system. It was fine until early July then one day it stated to cough fuel smoke and bog. Items I have done since this started to happen , not in any specific order…

1) checked fuel pressure 33 at idle 35-38 on the gas.
2) swapped ceramic circuit board inside the maf potentiometer
3) swapped air temp sensor inside the maf
4) installed nos engine temp sensor
5) installed nos fuel return check valve on tank
6) installed 1 coil for cylinders 1 and 4 
7) swapped out plugs
checked compression 125 to 130 in all 4 cylinders
9) swapped out the throttle position sensor with new
10) removed black box computer and looked for anything abnormal on the 2 circuit boards. Nothing abnormal seen
11) checked battery voltage is over 12v


I did each item separately and the results never changed. Mind boggling. Thinking it may be the black box computer letting too much fuel in. Thought it may be too much fuel pressure soaking the cylinder when the injectors open but the pressure seems in line of expectation. 

Any suggestions out there other than put carbs in? Anyone got a working bike they would be willing to test my black box in? That’s one thing I can’t verify.

Have you had the injectors tested, if they have a build up of crystallised fuel the needles can't fully return to their seats and seal. This will cause the injectors to "dribble" fuel constantly as long as there is fuel pressure (same as leaking choke plungers on carbs) also the fuel won't "atomise" as it should when the injector opens so will cause the injectors to "spit" rather than spray".
ECU faults are generally uncommon (my experience is with cars not bikes) but "bad injectors" get overlooked all the time. You can rig a test set up to see what's happening, if I get chance I will post a "how to" later
EDIT:
 

I would look towards the injectors. 

I did bench test all 4 injectors back in April,  they squirted a nice mist, I put some carb cleaner into each one and cycled them to verify no old build up. The injectors were off the bike in a box from 2004 to 2022.  I put the FI system back on the bike and thought to have it running well back in May but then this happened.  I will check them again for any new drips etc.. got nothing to lose!  Thanks for the info.

I removed the injector bank and turned over the bike.  All 4 jets are squirting nicely and there is no residual dripping on the injectors. I need to figure out how to post a video and pics here from my IPad as all the files on my iPad are larger than the limits.

Are those splices in the spart plug wires? I'd check for green stuff at the connections as well as the caps. 
Steve

Yes those are splices , the original wires are molded into the coil so I needed to cut them short and install the splices to replace the wires and cap ends.  Caps are 5k ohm and plugs are resistor.  

No kawasaki I know runs well with resistor caps and plugs. One or the other or none but definately not both!

Both is a sure way to foul plugs. 

Warren3200gt wrote:

No kawasaki I know runs well with resistor caps and plugs. One or the other or none but definately not both!

Both is a sure way to foul plugs. 



I agree but it was running ok back in May/June with the same set up.  Bike sat for about 3.5 weeks and when I started it, it was fouling and way rich. Put in brand new plugs and same result.  I will see if I can dig up some old non resistor ones for trying.   I started thinking coils, then ignition box etc.. but when I swapped the 1 coil with a known good one and no change, I crossed that one off the list.
 

Your injector test has proved you have fuel delivery (but you already knew that as the plugs are fouling) however testing in this way isn't going to give you the information you need. By cranking the engine the injectors are all firing 3 or 4 times per second and into a paper towel. The reason for the test method I suggested is so that you can hear a "clean break" when the injectors fire and also by using a glass jar you can see if there are droplets on the wall of the glass as well as being able to clearly see the spray pattern as you operate the injector for a few seconds instead of a fraction of a second. Old fuel injected motors can run well if they are functioning correctly but they don't have the benefit of modern electronics to compensate for things that aren't quite right so basics like spray patterns etc are critical (it would be good if you could find delivery specs so you could measure the actual quantity of fuel delivery from each injector (they do wear over time)
I'm sure you will get there in the end, be lucky

Wookie58 wrote:

Your injector test has proved you have fuel delivery (but you already knew that as the plugs are fouling) however testing in this way isn't going to give you the information you need. By cranking the engine the injectors are all firing 3 or 4 times per second and into a paper towel. The reason for the test method I suggested is so that you can hear a "clean break" when the injectors fire and also by using a glass jar you can see if there are droplets on the wall of the glass as well as being able to clearly see the spray pattern as you operate the injector for a few seconds instead of a fraction of a second. Old fuel injected motors can run well if they are functioning correctly but they don't have the benefit of modern electronics to compensate for things that aren't quite right so basics like spray patterns etc are critical (it would be good if you could find delivery specs so you could measure the actual quantity of fuel delivery from each injector (they do wear over time)
I'm sure you will get there in the end, be lucky


I will spend some more time on them,  in fact I was just thinking about trying slow motion video to try and capture the spray pattern. The last time I cleaned them I used a dc power supply to start stop with a momentary push button.  I will get that reconnected and try each one separately.  Thanks for the feedback.  

Cullen wrote:

Warren3200gt wrote:

No kawasaki I know runs well with resistor caps and plugs. One or the other or none but definately not both!

Both is a sure way to foul plugs. 



I agree but it was running ok back in May/June with the same set up.  Bike sat for about 3.5 weeks and when I started it, it was fouling and way rich. Put in brand new plugs and same result.  I will see if I can dig up some old non resistor ones for trying.   I started thinking coils, then ignition box etc.. but when I swapped the 1 coil with a known good one and no change, I crossed that one off the list.


 

If it's suddenly all four plugs it's bound to be electrical before it gets split into two for the coils. Have you got 12+ v at the coils? If not and two resistors per ignition line will only compound the condition.
Simple things to check and remedy first.