1975 Z1 900 spark plug question...

I am having a problem with plugs fouling on #1 and #4
cylinders but not at the same time like a coil problem.
It may foul #4 three times to #1 once. Has anyone ever
had to run one step hotter plugs on the outside holes,
A friend of mine had a 1000 Z1 Classic fuely that had
to have the outside plugs one step hotter to run more
than 250 miles. The last two NGK plugs that fouled
went completely dead, not even a weak spark, tossed in
a used plug from a dirt bike to check the spark and it
was great. There is plenty of blue smoke after it fouls
a plug but not until. Any ideas?

Post edited by: 762shooter, at: 2007/06/20 00:32

KZ900's were first produced as 1976's. But to answer your question my KZ always needed one step hotter plugs.

KZCSI

OK, Z1, anyway what plug have you had the best luck
with? I have a set of ND plugs in the cupboard but
they are two steps hotter so I am trying to shy away
from them, and I'm about fed up with NGK's. For about
the last ten years NGK's have been junk as far as I
am concerned.

762shooter wrote:

I am having a problem with plugs fouling on #1 and #4
cylinders but not at the same time like a coil problem.
It may foul #4 three times to #1 once. Has anyone ever
had to run one step hotter plugs on the outside holes,
A friend of mine had a 1000 Z1 Classic fuely that had
to have the outside plugs one step hotter to run more
than 250 miles. The last two NGK plugs that fouled
went completely dead, not even a weak spark, tossed in
a used plug from a dirt bike to check the spark and it
was great. There is plenty of blue smoke after it fouls
a plug but not until. Any ideas?<br><br>Post edited by: 762shooter, at: 2007/06/20 00:32

Too high fuel level in float bowls could cause the problem.

Thanks Patton, I will check that also.

Change the skinny little wire that feeds the coils with primary current to a larger wire. Also, the blue smoke tells me something else might be a problem here too. check the compression and watch the gauge closely the first times around and note the highest readings on each cylinder and how fast it gets there. Broken piston rings can hide in the cylinder and cause confusion. No blue smoke should be coming out the exhaust, that is oil and rings control oil so you know what that means. I've had these problems too in the past. Ask yourself also, "What is great spark"? If the compression is good and the carbs are set right and it still doesn't idle at 900rpm, the spark is weak.

Post edited by: nads.com, at: 2007/06/20 03:00

Do yourself a favor and troubleshoot the problem systematically. You had best eliminate ignition problems before going elsewhere... that is, fiddling with different types of plugs. I suggest you remove the 1/4 coil and swap it with the 2/3 coil. See if the problem moves. If the problem moves with the coil, you will have learned something. I would then replace the plug wires/caps and install some new NGK B8ES plugs even though you may be getting tired of doing this type stuff. If you do this and still have problems, also measure the voltage at the coil where the problem is occuring. Measure the primary and secondary coil resistance. If the resistance has crept up, your spark can get real weak. Anyway, eliminate ignition before moving elsewhere in troubleshooting... the problem on 1/4 indicates a possible ignition issue.

Wiredgeorge, I have changed the coils and have switched
them side to side with the same problem. NGK B8ES are
the plugs that are fouling. I am going to check the
compression and get back with the results.

are you still running the stock point set up, if so check the condensers and the points,while you are there look at the timing

Points and condensers have been changed with little
help. I did a compression test tonight on all four
cylinders, they were up to top pressure within four
seconds of turning over the motor, when I got the
results I then added a little oil to the holes and
the compression went up, here they are,

#1, 115 psi, 150 after adding a little oil
#2, 100 psi, 125 after adding a little oil
#3, 100 psi, 130 after adding a little oil
#4, 110 psi, 130 after adding a little oil

I would tend to agree that it is an ignition problem,
but it happens to #4 hole a lot more than #1 hole.
I will meter the coils again and see what I get, it
has been a while since I done that.

could be that #4 is a bit rich and with low compression it fouls that one first, check the pulg wires also, the connections get bad and cause miss fire