TOPIC:

Completed a cafe racer build on my 1980 KZ650F last summer. Has fired up first time for the past year with virtually zero delay. Always runs great. I was driving to my office the other day and it started sputtering and quickly died. I thought I was out of gas so after pushing to the station and filling it made no difference. I could get some occasional cylinders to fire but nothing serious. Trailered home after failing to resurrect in the parking lot.

So I’ve been going through everything I can think of. Currently I’ve done the following:

Fuel Supply

-Cleaned carbs - still all clean (only run ethanol free)
-Messed with idle screw positions
-Removed pods and used starting fluid

Spark:
-Adjusted timing 
-4 new plugs (be7s)
-Replaced both ignition coils
-All 3 fuses are intact
-Tested spark against engine block, all 4 produce bright spark

Compression:
-All 4 cylinders measure 150psi, +- 5 psi
-Haven’t torn into the engine yet but last year I adjusted valve shims. Have only ridden about 1000 miles since 

So I’m kinda out of ideas. I thought I knew this bike, inside and out. Not really sure where to go from here. Just tested with starter fluid again after doing all of this. Does anyone have any other ideas on what could possibly be wrong. I’m no longer getting any hints of ignition out of it. Fresh strong battery as well.

Thanks in advance (pic for attention)

 

Murphys Law, sounds like some a**hole have clogged your exhaust. My first guess...

Do you have a kill switch or anything similar that could be shorting out ?

are you running points?
 

Yes to points. Adjusted gaps along with timing and tested with multimeter and it lines up right with timing mark. I ruled out bad capacitors based on the fact that I get good spark at the plugs.

Maybe I’ll peek in the exhaust??

I mean, there’s the switch on the right handlebar. I did a parasitic draw test while the key was on but the engine (obviously) not running. I was getting 2-3 amps from one ignition coil or the other when testing in series at the negative battery terminal. When I moved the switch from “run” to “off” virtually all amperage disappeared. To me that meant that it was ready to go and the switch was functioning as intended.

During the troubleshooting, did you take apart the timing advancer?  It can go back together backwards such that you will have sparks on all four, but it won't fire up.  A similar issue would be if the black wire and green wire at the coils were somehow swapped.  Also, plug wires going to the wrong cylinder as well, (obviously).

Usually, on a sputter and die, my first go-to check is the wiring at the ignition switch. If it's original, I would check where the wires attach to the switch.  I've seen many failures there.  Sometimes the wire is hanging on enough to show sparks at the plugs, but during running, it fails.

wrote:

I did a parasitic draw test while the key was on but the engine (obviously) not running. I was getting 2-3 amps from one ignition coil or the other when testing in series at the negative battery terminal. When I moved the switch from “run” to “off” virtually all amperage disappeared. To me that meant that it was ready to go and the switch was functioning as intended.

Yes, that all sounds correct.

It's harder for spark plugs to fire under compression as opposed to outside of cylinder.
Are your condensors OEM Kawasaki?
Also, ohm out your plug, wire, cap combo.

You have compression and spark (when tested to ground) so this tends to make me think it is fuel (intake related).  Are the bowls getting fuel, are the plugs wet, is the petcock working correctly, is the vent in the tank cap clogged ? 

Also, verify your camshaft to crankshaft timing relationship.

Would this change spontaneously while driving?

anything is possible.
you basically have to check everything