no 2 cyl not firing when plug is fitted

[johnk]

..i have a problem guys my 1982 kz is driving me nuts , when i earth the plug to the engine it does not fire at the tip, how ever when i hold it slightly away from the engine it fires, when the plug is inserted into the engine the cylinder does not fire ...when i hold the plug cap a little back from the plug it fires.
any thoughts???   thanks

[Lucky 1]

Do not even use that method.

Just clip a timing light onto that spark plug wire when it is IN the engine,
 and watch for the flash of the timing light.

Just because you cannot see a spark does not mean there is none.
You could have a worn out condenser.

BTW This is a Honda website.

[Rich Ard]

Johnk:

1) New sparkplug

2) Test the coil and the condenser (which your KZ may not have - might be just the coil) with a multimeter (there should be instructions on how to do this in your manual; if not, it's easy to find instructions online)

3) If the plug is new, the coil and condenser check out, try removing the sparkplug lead from the coil wire, and holding it away from the engine like you would with the plug, and see if you get an arc. If you do, you need to replace the plug lead; if you don't, it's time for a new wire.

[Rich Ard]

Lucky 1 wrote

Do not even use that method.

Just clip a timing light onto that spark plug wire when it is IN the engine,
 and watch for the flash of the timing light.

Just because you cannot see a spark does not mean there is none.

I've seen this suggested here a couple of times - to use a timing light rather than pulling the plug - why would you do it that way rather than check with the plug itself? I expect to see a fat blue spark and wouldn't have it any other way. :)

[shultz_1978]

I would simply check and make sure the no 2 cyl is getting fuel. If you can choke it a little by hand. If it picks up then it is sparking. If not keep digging.

If it fires you have found you problem. NO fuel

[shinyribs]

Some coils wont tolerate that test. With no way of discharging, some coils will just burn out if tested with the plug wire off. If in doubt use a light. If not, pulling the plug and looking for that fat, blue spark is pretty fool proof.

[icerigger]

Yeah, the new high energy coils will self destruct if not attached to a grounded plug in as little as a single pulse. That's why most of them have severely limited warranty.

[TOOLS1]

Lucky 1 wrote

Do not even use that method.

Just clip a timing light onto that spark plug wire when it is IN the engine,
 and watch for the flash of the timing light.

Just because you cannot see a spark does not mean there is none.
You could have a worn out condenser.

BTW This is a Honda website.

I believe there is a CB 750 KZ in Europe, and the fact that he said he "earthed the plug" leads me to think this guy is in Europe.
TOOLS

[shinyribs]

1982 Honda CB750KZ  <---Tools rocks.As usual...

[johnk]

??

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On 29 Dec 2012, at 07:24 AM, "shinyribs [via Honda CB750'S]" <[hidden email]> wrote:

1982 Honda CB750KZ

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[Piute]

shinyribs wrote

1982 Honda CB750KZ  <---Tools rocks.As usual...

Not nothing about d o h c  but "looks" like the Annv.model