kz1000, 1978 A2 model, missing on cyl #4

The #4 cylinder is not firing consistently while all 3 other cylinders are fine.

I had just gapped then installed 4 new spark plugs; this bike had sat for 12 years and it's running after a carb clean, new oil/filter, new battery, and the CDI ignition is fine -- there's a healthy spark on the #4 cylinder. Also put a temporary patch on #2 header bottom, but #2 is not the problem here.

So besides the sound of the engine (you know how it sounds when it's dropping one of the 4 cylinders intermittently), here are other symptoms.

WHENEVER ONE OF MY BIKES IS DROPPING A CYLINDER, HERE'S THE E-Z STEPS I GO THROUGH to locate the missing cylinder and do a quick diagnostic check of its condition:

1) wait for a couple minutes for the header pipes to cool a bit so I can touch them briefly without getting a burn

2) find the 'coldest' header -- that's the cylinder that's dropping

3) pull the spark plug and note color on that dropping cylinder


In this case, my #4 header pipe is cold. Next I pull the #4 plug. It's wet and black.

Another symptom: I'm burning some oil, but only intermittently -- as I'm revving the engine, oily smoke comes out, but NOT ALL THE TIME.

I'M THINKING it might be a piston ring on the #4 cylinder trying to decide if now's a good time to unstick itself from the piston groove and start working. (This bike hasn't run in 12 years, and as of now it has only run for a total of 5-7 minutes since I started it after all the prep work.)

A piston ring that's stuck in its groove -- would that explain the oil blow-by and the fouled #4 spark plug, and the cylinder firing only randomly?

I doubt it's the coil, since that same coil is providing plenty of spark for the other cylinder it supplies (there are only 2 coils on a 4-cylinder kz1000, each coil supplies 2 cylinders).

And as I said, I checked for spark on #4 and it's fine.


ANY IDEAS WHAT ELSE IT COULD BE?

Did you check cold/hot compression on all cylinders?

I would also want to check valve clearances.

I would also put a timing light on the plug and watch it while you rev the engine and see if the spark is constant or if it is "cutting out" intermittently.

As you said:

In this case, my #4 header pipe is cold. Next I pull the #4 plug. It's wet and black.

I doubt it's the coil, since that same coil is providing plenty of spark for the other cylinder it supplies (there are only 2 coils on a 4-cylinder kz1000, each coil supplies 2 cylinders).

The two plugs fed by each coil are wired in series. If a bad ring oils up the #4 plug enough to keep it from sparking, #1 can't fire either.

bountyhunter wrote:

Did you check cold/hot compression on all cylinders?

I would also want to check valve clearances.

I would also put a timing light on the plug and watch it while you rev the engine and see if the spark is constant or if it is "cutting out" intermittently.

I have a compression tester, I didn't even think of that, thanks for the reminder. Will check tomorrow.

Not 100% sure I understand the timing-light idea.
Sorry, I'm new to timing lights, and as it turns out I just bought a brand new one to learn how to use them, and haven't even taken it out of the package. Now's a good time I reckon if I can figure out what you're saying.

Do you mean:

1) hook up timing light to battery and also to the #4 plug wire
2) start and rev the engine
3) if the light from the timing light does not flash consistently, but only flashes randomly or intermittently -- that indicates a sparking problem on #4.


Is that correct?

Get yourself a spray bottle of water, it will flash to steam at 212 F (safer than touching a hot exhaust pipe).

Replace the sparkplug caps if possible and the sparkplug wires(high tension leads for the Brits.) as both can fail under a load.

An ignition coil can also fail by giving a good spark on one port but not the other, try switching the ports around.

MFolks wrote:

Get yourself a spray bottle of water, it will flash to steam at 212 F (safer than touching a hot exhaust pipe).

Replace the sparkplug caps if possible and the sparkplug wires(high tension leads for the Brits.) as both can fail under a load.

An ignition coil can also fail by giving a good spark on one port but not the other, try switching the ports around.

Okay, my index finger's nerve endings will appreciate that water bottle idea there! Thanks.

Question about switching the plug wires around -- does that mean that the cylinders #4 and the other cylinder serviced by the same coil -- fire at the same time? I'm a newbie to coils and firing sequence, so I'm trying to see if you mean that the one coil that fires my 'dropping' cylinder #4 also fires the other cylinder at the exact same time?

If so, I can see how switching the plug leads for those two coil-in-common cylinders will help me check the coil real fast! Great idea. If the 'cold header pipe' symptom shifts when I swap the coil leads, that tells me a lot right there: if swapping that coil's leads has no effect, and #4 cylinder is still misfiring, it eliminates the electricals and indicates a mechanical problem instead.

Do you mean the one coil that fires my 'dropping' cylinder #4 also fires the other cylinder at the *exact same time*, making it safe to swap plug leads between those 2 cylinders?

The big Kawasaki's have a wasted spark. On the Kz 900's,1000's and 1100's the left ignition coil fires #1 and #4 at the same time, while the right ignition coil fires #2 and #3 at the same time.

Try moving the sparkplug wires from one port to the other and see if any change takes place.

newOld_kz1000 wrote:

Do you mean:

1) hook up timing light to battery and also to the #4 plug wire
2) start and rev the engine
3) if the light from the timing light does not flash consistently, but only flashes randomly or intermittently -- that indicates a sparking problem on #4.


Is that correct?

that's it.

newOld_kz1000 wrote:

MFolks wrote:

Get yourself a spray bottle of water, it will flash to steam at 212 F (safer than touching a hot exhaust pipe).

Replace the sparkplug caps if possible and the sparkplug wires(high tension leads for the Brits.) as both can fail under a load.

An ignition coil can also fail by giving a good spark on one port but not the other, try switching the ports around.

Okay, my index finger's nerve endings will appreciate that water bottle idea there! Thanks.

Question about switching the plug wires around -- does that mean that the cylinders #4 and the other cylinder serviced by the same coil -- fire at the same time? I'm a newbie to coils and firing sequence, so I'm trying to see if you mean that the one coil that fires my 'dropping' cylinder #4 also fires the other cylinder at the exact same time?

#1 and #4 spark at the same time, #2 and #3 also spark at the same time (180 degrees away from 1/4).

I think the cams are such that the 1/4 pistons actually fire (produce energy) 180 out from each other, but the plugs spark on every upstroke regardless of whether it is compression or exhaust. The 1/4 piston set moves in unison but one is compressing on the upstroke while the other is pushing out exhaust. That way you get all the power strokes equally spaced out for smoother running. The 2/3 piston set is 180 out from the 1/4 set.

ah-HAH. So that's the 'wasted spark'.

Well thanks to all for pointing this out. It makes sense to have the spark going off everytime the piston comes up. It keeps the electrical bits simpler in their design, because more parts or more *complex* electrical parts would be required to have no spark on the exhaust up-stroke of the piston. This way, the spark plugs are firing as if the motor was a 2-stroke -- every time a piston goes up the spark fires. No harm done on the exhaust stroke, no compressed fuel/air mixture to fire anyways.

So tomorrow, I will do a quick swap of the #1 and #4 plug wires and start the bike up, and if the 'cylinder not firing' problem stays with my #4 cylinder, I'll next do a compression test of all 4 cylinders.


ANYONE KNOW WHAT THE COMPRESSION GAUGE SHOULD READ?

And since I've only done compression checks on 2-stroke street bikes, I have a question about the *process* for doing it on a 4-stroke bike.

On a 2-stroke like an rd400 or H1-500 triple, you connect the compression tester, open the throttle wide open, then kick it over (ignition off of course, with all other spark plugs removed) till the compression gauge needle stops going up, usually about 5-6 kicks.

How do you compression-test a KZ motor? Is it the same?

And what should the reading be for a 1978 kz1000 engine?

Same compression test procedure as described, and may use either electric starter or kick starter to spin over the engine.

128~156 psi, with service limit of 100 psi.
Cylinders are supposed to be within 14 psi.

But some engines run surprisingly well with less than 100 psi and larger variance among cylinders.

Remember to check and adjust valve clearances.

And a leak-down test would be even more informative.

Good Luck!

I'd say the minmum would be 120 PSI and 150 PSI would be great. The same test is done on four strokes, wide open throttle and either kick it over or use the electric starter(pull the sparkplugs to make testing easier).

I like using the screw in type of gauge as the rubber push on ones are hard to hold while kicking it over.

Patton wrote:

Remember to check and adjust valve clearances.

And a leak-down test would be even more informative.

Good Luck!

How are the clearances checked? I'm guessing you remove the valve cover and use a feeler gauge to measure the gaps between the shims and the cams?