'80 KZ750 E1, middle two cylinders not firing

This has been an intermitant problem over the last couple years.

While riding or sometimes at start up the middle two cylindes will either stop firing or not fire at all (upon startup).

When cruising normally the volt meter will read about 12 and every thing is great. Then the engine will bog and it will not stay running at idle. I notice that the volt meter reads 14. I shut down and get off and feel the exhaust pipes to see which cylindres are not firing. The two outside cylinder pipes are normal the middle two are cool.

I can ride around in this condition with almost no power and milking it at idle to keep it running.

Usually it has fixed itself within a couple minutes but yesterday it remained failed for the entire ride.

I will look at my shop manual when I get home but any advice will be appreciated. I really don't know where to look in the manual. I was going to start with ignition system.

I found it strange that the volt meter indicated increased generator output while the ignition seems to be failing.

Thank you,

Josh

1st.Most plausible: Ignition Coil Failure
While warming up,...the coil will expand due to heat and if one of the wire's is broken, the first crack initiation
will grow wider and then it is "game-over".

2nd. The +/- connection to the ignition coil fails.
(check wire and connectors)

Switch the coils the problem should go from 2 and 3 to 1 and 4. you also can do a resistance check the input should be around 4 ohms and the output 23,000 if your running points for a cdi check the manual for sure. I think for cdi it should be around 2 or 3 ohms input 15,000 output

You didn't mention if these coils were stock or aftermarket ones like Dyna makes.

If they are stockers, once they start to die they have to be replaced as you cannot do much in the line of repairs as they are sealed. You might be able to trim back a bit of length on the plug wires but that is pretty much it.

With the Dynas you can change plug wires and connectors which is always the first (and easiest) thing to check when the coils start acting up.

As mentioned, pull the tank, swap the 2-3 coil with the 1-4 coil and if your problem moves to the other two cylinders you have pinpointed the problem. If this is the case, give Jeff @ Z1 Enterprises a call and put some Dyna coils on the bike. A little peace of mind with new technology is better than getting stuck on the side of the road with 28 year old electronics.

Cheers-Colin Firth-Ontario Canada

1977 Kz650 Custom bought new by brother. Latest rebirth includes, Wiseco 810 big-bore, milled, ported and polished head, GPz 750 cams, Gpz intake valves, 900 drag bike springs, Mikuni 29 Smoothbores (courtesy of WiredGeorge) Dyna coils, Dyna electronic ignition, Velocity stack, Mac Pipe, 130 rear tire, Barnett Clutch, 14 tooth primary drive sprocket, stainless braided brake lines, sculpted seat, superbike bars, Bridgestone Spitfire tires. Factory matching Moon Dust Silver paint job. Looks stock but it will surprise most bike up to 60 mph.

1982 Ferrari 308Gtsi -3.0V8, quad cam, Rossa Corsa Red with tan leather. 54K miles
2007 Toyota FJ Cruiser - V6, 6 speed. Yellow and awesome
1998 Jeep TJ Six banger with 5 speed
2006 Chevrolet Uplander - Cause I needed to have something ugly in my driveway:-)

Thank you all for the advice. I removed the left coil and had it bench tested. Of course it worked fine. I will now swap it with the right and see what happens.

Thanks again,
Josh

The problem went away for about 5 miles then returned but did not follow the coil. So now I am suspecting a bad ignition pick up for cylinders #2 & #3.

Where can I get a new set of pick ups?

If not already done, would remove all plugs and visually inspect quality of spark. A good strong spark indicates the ignition system is okay. Best to use four brand new plugs.

While plugs are removed, would also perform compression test (remember to hold throttle wide open).

Would also assure valve clearances are within specs.

When satisfied that ignition, compression and valve clearances are okay, would then use clear plastic tube test to verify correct float bowl fuel level in carbs.

Good Luck!

When cruising normally the volt meter will read about 12 and every thing is great. Then the engine will bog and it will not stay running at idle. I notice that the volt meter reads 14.

Interesting that the current draw on the system drops at the same time you lose the two cylinders (one coil).

So it appears that one coil is dropping out of the circuit, like maybe you have a bad power connection, or a bad connection between the coil and the igniter.

The ignition pickup only tells the igniter to turn the coil off, otherwise the coil stays on (drawing current) all the time, so I don't see how a bad pickup could be the problem.

I suggest giving the wiring a complete inspection.

Thanks again for all the help. I think I have reached the end of my technical abilities. I can take stuff off and put it back on but inspecting wiring with a volt meter is aabove my head. I tried to cherck the continuity of the pick-ups last night but couldn't figure out hhow to get the volt meter to show connection. After I re-hooked up the 4-pin connector the bike idled perfectly for a while. I'll ride it today and if it fails go to the Kawasaki shop. They said they would check the pick-up continuity while I wait especially if it is in the failed mode.

Thanks again.

Josh

Might only just need a set of brand new spark plugs.

Good Luck!

First off I'd clean and check the electrical connections. Micro brushes, a Dremmel with a brush or barrel file , I have a thick piece of thick wire that I roughed up with a grinder that seems to work best. Then gently pinch the female connection..GENTLY! Work a little di-electric grease into it and reconnect. Bro built a lot of bikes and that is the first thing he did to these old gals.

Which connections? I can clean and grease the:
4 pin connector
the coil connectors (not the spark plug wires)

WHat other connectors in regard to the ignition system do you suggest I clean/grease?

I will clean and gap the plugs but because the failure is always cylinders #2 & #3 simultaniously and the plugs were new about 1000 miles ago I ruled out the plugs being the problem. However I appreciate the suggestion and will remove clean / gap and replace in different order just to be sure.

I rode 20 miles this morning and it failed intermittantly but started the failure sequence at idle then got itself out of it.

Thanks again for all the help.

Josh