Re-Visiting the Runs like sh*t 81 GPz550

The beater 1981 GPz550--STOCK--still will not come around.
Carbs are clean.
Good spark on all plugs.
Good compression
The advance/pick up is working
The timing is spot on.

Still runs like crap on the center two cylinders.

It's frustrating as all hell. The carbs are clean! There is good spark! There is good compression!

 

Have you checked "valve clearance" (big gaps will mean the valves open less ?)

Not in a while but I guess I can.

The good compression all the way across leads me to believe that the valve clearance is good. Is that a bad thing?

 

chopper1963 wrote:

Not in a while but I guess I can.

The good compression all the way across leads me to believe that the valve clearance is good. Is that a bad thing?



 

Tight valves will effect compression, loose ones "not so much"
Is it possible to see into the carbs when the motor is running, if so are all four slides lifting equally ?

With good compression, clean carbs, and strong spark, I don't know what's left?  Could the center two exhaust pipes be plugged up?  And when you say clean carbs, did you ungang them and soak the bodies in carb dip after removing all the various parts?  Shoot carb spray through the pilot passages, and make sure it comes out the proper location on each carb?

I'd take a good look at the plugs, wires and coil. Have you used a timing light on them? You can look for a miss that way.
Steve

Going to take a wild guess here but i have ran across a couple Kawasaki 4cyl KZ750's that also had seemingly decent enough to start compression. Only to find out later that the head had warped, lifting 2 and 3 off their head gasket. But that's just a wild scenario i know. Being it's confined to 2/3 issues try swapping coil leads around and see if problem goes to 1/4. Have also experienced issues with the IC IGNITER and pick-ups on your era of Kawasaki. While it seemed to have decent enough spark still didn't function correctly. Switched out to a Dyna S and problem mysteriously disappeared, ha.   

If it's cylinders 2 & 3 that points to the one thing they have in common: the coil. @Asphalt900 has good advice there. Otherwise, I would suspect the pilots are not clean on those carbs. 
Question: How do you know the center two cylinders are not running well? 

<<<The timing is spot on.>>>

ThatGPzGuy wrote:

 
Question: How do you know the center two cylinders are not running well? 
 

That is a good question. An infrared thermometer (~$15 from Harbor Freight) will show the temp variances in the headers - a useful piece of info.

Bike runs on four top and mid range. But won't run on center two at all at idle. So frustrating

chopper1963 wrote:

Bike runs on four top and mid range. But won't run on center two at all at idle. So frustrating

Makes me suspect pilot circuits, either clogged or damaged. Perhaps mixture screws with broken tips, pilot jets wallowed out or pilot passageways gouged out by too-rough cleaning?
If the low speed mixture is way off, either lean or rich, those cylinders will not fire until the rpm is high enough to transition to the main circuit.

As asked above, how are you sure the middle two are the ones not firing at idle?