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I recently changed my stock Harley spark plugs and went with the Drag Specialties brand. I’m not sure if I gapped them incorrectly. But I had very poor performance out of the bike so I took them out and noticed there was a pitting on the top of the rear plug. Any suggestions of what I did wrong? New plug I put in The plug on the left was the old one. The plug in the right is the Drag Specialties plug. That I only put about 50 miles on.
I cannot offer any advice or comment on the Drag Specialties plugs. I've never used them.
IMHO.... For a street bike that's not racing, the standard Harley 6R12 plugs are all you need. They are usually very reasonably priced at a dealer. If you want to save a few dollars, Champion makes the Harley Twin Cam plugs, and the Champion RA8HC is the same plug... not just an equivalent, but the same plug.
They should be gapped .038" - .040"
You can buy more expensive plugs of exotic metals (platinum, Iridium, etc) but they just extend the service life. They don't really affect the performance. The OEM or Champion plugs are copper plus, inexpensive, and easy to change out. I don't feel the need to use anything else on my Twin Cams engines.
I currently have 4 Twin Cams. All have the HD 6R12 or Champion RA8HC Copper plus plugs. I inspect & change them frequently. I use them on one 88" Stage I engine, one 95" Stage IV engine, one 96" Stage I engine, and on my bagger with a 124" S&S crate engine at 135HP & 151TQ. No spark plug problems on any of those bikes.
The Champion RA8HC plugs cost $2.99each at my local Napa Auto.
One note:
The ION sensing knock detection started with the Delphi EFI systems in the 2001 Softails. So if you have the EFI version of your 2001 Deuce, you have to worry about non-OEM plugs, plug wires, and coils not playing well with the ION Sensing system. If they are not compatible with the system, they can detect spark knock where none is present and retard the timing, which equals a loss of performance.
A search could lead to hours of reading, but open the link below, go to Foxtrapper's post, #5. He gives a very good, succinct explanation of the ION Sensing System. We have found that it's not as "finicky" as first believed, but issues with non-OEM parts mentioned above, have been reported.
How was the bike running before change? That old plug on left although you don't show gap looks like something that has a good working FI system.
What does your gap look like? Most plugs come close these days. But of course should be checked?
Is that pits or aluminum?
You Harley will do better running on Harley's branded low resistance plug. You don't want a long life type plug. Couple new plugs ever 10,000. Good to go.
When I checked a NGK and Champon plugs with my OHM meter, thay had more resistance than the spec Harley's plug. (Resistance is built into them to stop radio interference I think)
My 04 FI has ION sensing for spark knock control. Runs fine on midgrad or premium fuel in hot weather. My bike seemed to run fine with the NGK but that was relatively level coastal areas and I drive easy.
PS..Welcome to the HDFORUM.
Last edited by Jackie Paper; Nov 28, 2024 at 03:55 AM.
That looks like FOD damage. FOD is foreign object damage. It sure looks like something hit that electrode. I would be using a boroscope and looking in that cylinder before doing any further running
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01 Softail deuce
