Too Lean?

Noticed yesterday on ride that she seemed a bit lean at near full rpm e.g. main jet circugit.=14pxPulled plug for a look.
Cylinder 1 is far and away the worst looking plug. Not sure why it's black around diameter.
Oil consumption has dropped to *nearly* zero, but me thinks cylinder is the burner.


From my POV, 4 is optimal followed by 6. Worse is 1, 3.
 

Thinking about running a slightly colder plug, BP8ES on 2 - 6.
 

 Of course, this is running around at sea level, and pretty sure this motorcycle will never receive death Valley or lower elevations. Still, I sure don't want a hole or piston.

Note: Stock jetting, but 6-1 DG Exhaust.
 

The last time I pulled my plugs, they all looked like your suspected lean ones and I have not altered the settings other than the idle mixture. I assumed that it left the factory that way. I'll pull mine again in another 3K or so when they're due for a change and see how they look.

Ted wrote:

The last time I pulled my plugs, they all looked like your suspected lean ones and I have not altered the settings other than the idle mixture. I assumed that it left the factory that way. I'll pull mine again in another 3K or so when they're due for a change and see how they look.
 

Thanks for the reply Ted. I have ordered some BP8ES plugs, a tad colder and will report back when my temp work gig ends in about 8 weeks.

I would have thought that the spark plugs are just showing the symptom ( slightly weak mixture) and are not the cause.   I’m sure you know far more than me about these carbs, but are all the needles the same size / taper, and do they have the same thickness of little washer under the clip? 
I guess incorrect ignition timing need not be considered, as two of your plugs are not white.  Just ignore me if I’m talking ********.!

Back from the work gig. Did some romping and stomping on the mighty KZ, including some pulls to full red line. Ran here in 4th on a slight uphill at 5k rpm for about 2 minutes, hit the kill switch, coasted to trailer, let her cool then pulled plugs. Me thinks too lean. Also, at full song, she kinda felt like a 2 stroke kx500 I had right before seizure.. Kind of hard to describe, but just a feeling of too much power for throttle setting.

Anyway, good to be back and hope all is well in your world!

 

Yup, running way too hot for a carbureted engine. I'm starting to wonder if the bikes that are running white hot are having fuel flow issues and leaning out when pulling heavy at high speed causing the float bowl fuel levels to drop which will lean out the mixture. Just putting that out there for thought.

Although Kawasaki doesn't have a "spec" listed for fuel flow testing, it can be worked out. In general, 1/2 pound of fuel /hour / horse power is a good general number to work with, so doing the math, 

120hp x .5 lbs fuel = 60 lbs/hour.
A US gallon of gas weighs 6 pounds, so 60 lbs/hour / 6 = 10 gallons / hour.

So let's say you wanted to do a fuel flow test. a reasonable time for the test could be 30 seconds. 1 hour  (60 minutes) / 1/2 =120.
1  US gallon = 128 ounces
10 US gallons = 1280 ounces 

1280 ounces /hour divided by 120 = 10.66 ounces in 30 seconds.

Bottom line - If you popped off the fuel line at the carb and did a fuel flow test for 30 seconds, you should be able to collect 10.66 ounces of fuel ( or more) to sustain 120 horse power without leaning out.

if the collection after 30 seconds is less than 10.6 OZ then either the fuel strainer in the tank on the fuel shutoff valve or the inline fuel filter is clogged or the vent to the fuel tank is blocked and you could test for this by taking a fuel flow test before the inline filter to eliminate the inline filter. If the flow is still to low, then the next would be to  confirm the vent tube in the fuel tank is clear. There probably isn't a way to remove the fuel strainer on the inlet of the fuel shut off valve without damaging the strainer, so I would say a very careful inspection of the strainer with a light and a magnifying glass may be in order. Remember that the purpose for the fuel strainer is to trap debris that could enter the tank so that the debris can't harm the fuel shut off valve seal faces. It's not there to remove debris for the specs required to flow through the passages in the carb.

That's my 2 cents ++++