Iridium plugs

[maybe73]

My buddy has a 1978 cb750k, running stock points, after market coils. It was time to replace spark plugs so he tried NGK iridiums, and now he has a mid rpm range stutter and hesitation. Coincidence or are these plugs meant to be run with electronic ignition? He is going to put standard ngk D8ea back in to see if it clears up. I was wondering for my own piece of mind. Thanks.

[TOOLS1]

I have never had a problem with them like this. They were designed for points ignitions. Was anything else done to the bike when the new plugs were installed?
TOOLS

[maybe73]

Nothing else was done except the plugs. He had just filled up with gas, that's probably the culprit.

[Re-run]

It is definitely possible it is the fuel or debris in the fuel. I had bad fuel in my fz once and I would be riding along and suddenly have a stutter every so often. Cleared up as soon as I put in good gas.

It MAY be possible that during the plug change, the wires got pulled out of the boot(s) slightly and could be causing the misfire. Not likely, but possible.

Iridium plugs are great things. They were not made for points per say, but are made to be more efficient and thus make better use of spark energy, thus the low power points ignition works better with these plugs than typical copper plugs. Did you friend gap the plugs before he put them in? If so, that is probably the issue. The plugs are pre-gapped and should not be messed with unless absolutely necessary. Or it may be possible that a plug is bad, but still that is unlikely.

[maybe73]

All possibilities. Great direction to start with. Thanks.

[mikeyboy1]

for what it's worth; I side gap the plugs on my 78 K & my 76 F. they work beautifully

[Re-run]

I think the issue is that many don't gap plugs properly and break the electrode. It is pretty thin so it doesn't take much. Still, generally speaking, the gap is usually already set. usually.

[maybe73]

My buddy put back in a new set of NGK D8EA plugs and it runs great again. He says he doesn't know why but the Iridiums didn't work for him, I said give them to me and I'll try them. Curiosity more than anything.