Consuming Spark Plugs

Hey All

Spent too long today trying to start her up after fresh rings, hone and lapping; found 2 open spark plugs were my devil all day..

They read infinity on the ohm meter between the terminal and the central electrode. I thought perhaps carbon may be stopping me from getting a reading, but even after a good brass brush up & shine; these are open. Other 2 are fine.

I recall last summer I would repeatedly find plugs that had gone open. Bike would suddenly be running like crap, find an open plug, replace it, and back running.

These are NGK B8ES.

Anyone seen this? What makes plugs do this? Is there a bad lot of NGK out there? or...?

Chris

Never seen that but the spark plugs on my wife's Saturn used to fail and the insulator would crack and disintegrate.

Using a brass brush leaves metal on the insulator causing a short. Plugs can be bad even new.
Steve

Once I had an NGK plug that refused to work after getting really wet with gas and someone else here reported similar and I can't understand how that might happen .

I have had the same NGK B8ES plugs in my bike for several years.

I had problems with NGK plugs. I switched to ND Hot-U (I think they now are called Denso U-Groove) and the problems went away. Ed

I only used the brush to scrape any carbon to ensure i was getting a good reading on the electrode. I could not believe I had another two open plugs on my hands & wanted to be sure of my measurements.

There is a small number stamped into the side of these on the socket hex. The two good plugs are stamped M426. The two bad plugs are stamped M444. Probably a date / lot code of some kind...

This has to be the fifth or sixth NGK plug in the last 12 months gone open on me. Time for a new brand to see if things play any better I guess.

I guess NGK like all other manufacturers are cheeping out on their brands now days. In the early 70's Honda had ND's in their 750 fours. Kawasaki ran NGK's. The ND's were junk but in an article I read, the Honda coils had a "longer" spark so the ND's would work. ND came out with the Hot U to solve this problem with other makes. I have a set of CB 750 coils I bought on eBay in 13. They were advertised for the Z1 but THEY AREN'T KAWASAKI and I told them so. They tested good so I kept them as spares. 5 OHM. I used Platinum plugs when I was burning oil. Once I fixed the problem, I went back to B8ES's.
Steve

It isn't unique to a single brand or series of plug. Many plugs have 2 (or more) piece center electrodes that can break or become separated. When this happens you'll read open circuit checking from center electrode to tip however the spark will jump the gap in the middle for a while given enough voltage. The metal in there is not the same as what is present at the tip and erodes while the spark jumps the gap until eventually the plugs fail completely.

That was an old dirt bike trick for fouling plugs. Only temporary. Make a gap to make the spark hotter.
Steve