Spark Plug Issues

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Jan 24, 2021 | 06:52 AM

#11

Dan89FLSTC

Seasoned HDF Member

Joined: May 2008

Posts: 21,143

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From: South Carolina

Quote:

Originally Posted by bklynbob

You might want new wires if you still have the originals.

If there is no misfire, I would leave them alone.

My `89 Softail still has the original wires...

Jan 24, 2021 | 07:08 AM

#12

roussfam

Seasoned HDF Member

Joined: Jan 2009

Posts: 12,686

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From: Ottawa, Ontario

NGK does not recommend gapping Iridium plugs. Tip is too fine and you could damage them.

https://densoautoparts.com/spark-plug-installation

You say the bike is harder to start, does it run ok once started?

Jim

Jan 24, 2021 | 07:33 AM

#13

Shotgun

Advanced

Joined: Aug 2005

Posts: 72

Likes: 10

From: Calgary, Alberta

Iridium plugs need a higher voltage to fire correctly. The H-D coils don't put out quite enough juice to properly fire these plugs.

Jan 24, 2021 | 08:59 AM

#14

Krobinson

Thread Starter

6th Gear

Joined: Dec 2020

Posts: 11

Likes: 1

From: TX

Quote:

Originally Posted by roussfam

It runs great after starting. The HD plugs I had in were fouled so I replaced them. I'll just put a new set of HD plugs in and go from there. The wires have been changed previously and I am not having backfires while riding; just misfires when trying to start the bike.

Jan 24, 2021 | 10:26 AM

#15

EdwardK

Road Warrior

Joined: Nov 2007

Posts: 1,800

Likes: 307

From: Houston, Texas

I asked the parts guy for the platinum plugs once and he asked me if I had any high performance mods to the engine. I told him no and he said in a stock motor they don't work any better than the standard plug and suggested I save the money and use the standard plug. My well respected indy uses Champion,

As others have mentioned, iridium plugs are very sensitive if you try to adjust by prying in-between the wire and the ground. Only adjust the ground.

Harleys can also be sensitive to aftermarket plugs because they read the plug as part of the anti knock system.

My suggestion would be to toss the expensive NGK iridium's for some cheap HD, Champion, or even plain Autolite's.

Jan 24, 2021 | 10:41 AM

#16

svarnster

Road Warrior

Joined: Jul 2011

Posts: 1,936

Likes: 310

From: coastal sc

I read that the previous plugs were fouled. I would be looking at fuel issue. Was bike hard to start just prior to plug change? I run the ir ngk with no issues. I would buy a set of stock plugs and try them to see if it helps. Cheap way to find out.

Jan 24, 2021 | 10:53 AM

#17

smitty901

Seasoned HDF Member

Joined: Feb 2008

Posts: 22,999

Likes: 11,439

Forget the fancy plugs just use plain old plugs. magic performance plugs just cause problems.

Last edited by smitty901; Jan 24, 2021 at 11:12 AM.

Jan 24, 2021 | 11:46 AM

#18

eighteight

Seasoned HDF Member

Joined: Oct 2019

Posts: 10,804

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From: OH

[QUOTE=svarnster;19688058]I read that the previous plugs were fouled. I would be looking at fuel issue.

i would suggest solving the CAUSE of fouled plugs first also

gas fouled? Oil?

In a correctly running engine they last a LONG time

jmo

Last edited by eighteight; Jan 24, 2021 at 02:20 PM.

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Jan 24, 2021 | 11:52 AM

#19

Krobinson

Thread Starter

6th Gear

Joined: Dec 2020

Posts: 11

Likes: 1

From: TX

Quote:

Originally Posted by svarnster

I would get an occasional misfire before changing the plugs, but no issues like I am having now. I'm guessing I should have left the gap on the NGK plugs alone and they would have worked out fine. I have 37,000 miles on my bike and I'm not due for changing out the fuel filter according to the service manual so I wouldn't think that would be an issue unless it just didn't last the length of its expected service life. The bike came with a 1450, but it has a tuner, upgraded pipes and air filter, and is now displaced at 1550. Not sure if that has any impact on what spark plugs I should be using?
My bike also sat for about 6 months or so while I worked on changing out the drive belt and clutch cable. This job resulted in all fluids (engine, trans, primary) being replaced so fouled oil can't be an issue. I have only ran about one tank of fuel since getting it back on the road and I have always ran premium fuel.

Last edited by Krobinson; Jan 24, 2021 at 11:57 AM.

Jan 24, 2021 | 01:33 PM

#20

Dan89FLSTC

Seasoned HDF Member

Joined: May 2008

Posts: 21,143

Likes: 12,707

From: South Carolina

Quote:

Originally Posted by Shotgun

Iridium plugs need a higher voltage to fire correctly. The H-D coils don't put out quite enough juice to properly fire these plugs.

You might want to check with any spark plug manufacturer about your theory...

Fine wire plugs require much less voltage than a standard plug.

I see no sense in spending more than I need to, I use OEM plugs.

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