Defective spark plug??

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Oct 26, 2015 | 07:52 PM

Sierra977

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From: Windwardside, Saba N.A.

Defective spark plug??

Today replaced both spark plugs in the 120R. On advice of mechanic, running standard V-Rod plugs (10R12A/32335-04).

Heat range looks okay for street with white insulator and minor staining on top of ground electrode. Gapped 0.038" and torqued to 18 ft lbs with thin film of Permatex anti-seize. Plugs have 800 street miles on them. Shell 93 octane gasoline exclusively.

Looking at front spark plug with viewer, the center electrode appears to have a section of the electrode trying to "flake off". As this is vary hard metal, having a piece approximately 0.100" flying around in the combustion chamber seems like a bad idea and a good way to score a wall, screw up a valve seat or chip a compression ring.

Wish I could post a pic but have doubts about my ability to get an acceptable image through camera and viewer lenses.

Anybody experience a chipped or flaked center electrode?

Taking plug(s) to dealer chief mechanic in the morning to get his opinion.

Oct 27, 2015 | 04:02 AM

Next In Line

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Wouldn't it be faster just to buy new spark plugs to do a A/B test?

Oct 27, 2015 | 06:15 AM

Hillsidecycle.com

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We use NGK's here.
No issues.

Oct 27, 2015 | 06:47 AM

Sierra977

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From: Windwardside, Saba N.A.

Quote:

Originally Posted by Next In Line

Wouldn't it be faster just to buy new spark plugs to do a A/B test?

Spark plug(s) still worked fine so an A/B test wouldn't show anything. Potential problem is if the "chip" from the center electrode broke off and started bouncing around the combustion chamber.

Don't think the engine is having preignition issues. It's been dyno'ed at the dealership but with ion-sensing all that really accomplished is mapping the fuel/air.

Yes there are NGK Iridiums on the shelf, but I've never gotten an answer to the question of how NGK's work with ion-sensing so there they stay.

ETA about pre-ignition... The "chip" has a very sharp edge near the insulator, like the separation started there. That sharp edge surely runs hotter than the rest of the plug. If that hot spot is causing mixture to burn early and ion-sensing is doing its job, engine could be losing ignition timing and I just don't know it.

This is really a spark plug mechanical quality question. I'm good at reading spark plugs. Do it all the time for race cars. In all the years, I've never seen a spark plug in the process of flaking off a section of the center electrode. Even from engines with severe pre-ignition problems. Fractured insulators yes but not center electrodes.

Guess I need to start doing pre-install visual checks on the spark plugs. May as well start doing resistance test too... Setting the gap used to be sooo easy.

Last edited by Sierra977; Oct 27, 2015 at 07:05 AM.

Oct 30, 2015 | 06:58 PM

Billyram

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From: South Carolina

My bike runs best with NGK's.
Billy

Oct 30, 2015 | 11:31 PM

HD Bobber

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From: Illinois

Quote:

Originally Posted by Hillsidecycle.com

We use NGK's here.
No issues.

Quote:

Originally Posted by Billyram

My bike runs best with NGK's.
Billy

NGK Iradium plugs here.

Nov 1, 2015 | 08:28 AM

Sierra977

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From: Windwardside, Saba N.A.

NGK Laser Iridium DPR8EIX-9 and DPR7EIX-9 plugs are in the parts box. Going to try the 8's next plug change, read the plugs then maybe move up the heat range to 7's.