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The OEM H-D plug is best from what I understand - I got a set of brand new Iridium plugs if anyone wants them cheap - I never should have bought them if it's true that the OEM plugs should be used for proper ION knock sensing and ignition retard operation.
Ron Babos can you chime in please ? Color looks good to me - not white lean, not black rich - pretty much a tan color but if the engine hasn't been run at full throttle then shutoff there's no telling what WOT color would be so that color you have would be a snapshot of normal overall operation - which looks pretty good (y):cool:
 

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I wouldn't say the plugs look lean and it could be the lighting when taking the pic. The reddish color usually means there's a fuel additive of some form being used. There is absolutely no gain from branching away from stock plugs but you can get a negative as in knock control might be lost if ion sensing is lost. Spark plug power gains are a myth.
Ron
 

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Might be it's the smaller diameter of the iridium fine wire electrode ( vs the standard massive electrode plug ) that sends the wrong signal back for ION knock sensing, added to the different resistance ( as coastrider said ) that causes the problem. I've got a note to self on my NGK Laser Iridium KR8AI 5477 Plugs that says " do not use - 3K Ohm bad vs 22K Ohm good on H-D 32186-10 or NGK DCPR8E " . You would think NGK would not sell a spark plug that defeats something as important as knock sensing for a street ridden M/C so maybe Iridium plugs are intended for drag racing applications only, where maybe fuel quality and tuning are much more closely watched ? Thoughts ? Suggestions ? (y) :cool:
 

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I have always preferred split fire plugs like your old ones…as they can be more efficient and get you marginally better power via improved burn profile with two sparks; one on each side. You don’t show the electrodes on the news ones…but I would go with split fire like your old ones.

But, one also needs to understand how plugs function…as they just take electrical energy and create sparks to ignite the fuel/air mixture. So, I inspect, clean and gap mine on a regular basis…but don’t always see a need to replace them just because x time or miles have occurred (besides it also depends upon how your miles are done as they fire on an RPM basis and not miles…so lots of racing, starts, etc. are harder than highway cruising in high gear/lower RPM).

Finally, I also remove the plugs, replace the plug wire on each and place them against the cylinder head for grounding and then crank the engine to see the plugs spark (best done when it is darker). But, as much as marketing wants you to believe there is a huge difference…or need to replace them, so long as they are creating a strong spark (preferably split fire spark), they are mostly fine for normal riding.
 

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plugs are easily fired when not under compression. Good test to see if it's firing, but doesn't mean it's good under compression.....
True. In the old days, shops had cleaners plug testers that ran compressed air pressure on them while sparking to check them. You could view in the glass window, the odd plug start to miss as the pressure was cranked up.
Ron
 

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Hell, I've flown with plugs older then me. As long as they gap ok, pass the test, they go back in.
Aircraft plugs must be big bucks? I guess when a plug fails mid-air, you just pull over to the nearest cloud and call AAA. For what it costs for a standard plug, I'll just change them every year (need to see what's going on with combustion anyways). On my Hemi Rams, I follow the change intervals (16 plugs = $$).
 

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Aircraft plugs must be big bucks? I guess when a plug fails mid-air, you just pull over to the nearest cloud and call AAA. For what it costs for a standard plug, I'll just change them every year (need to see what's going on with combustion anyways). On my Hemi Rams, I follow the change intervals (16 plugs = $$).
Dual ignition. You do a run up check on the ground and test each system, then go to both for blast off. If one side is missing, judgement call, fix it there or fly home and fix it later. You wouldn't even notice a plug crapping out in the air since engine will run perfectly fine on one system. Ball park cost for one plug is about $70.
Ron
 

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You wouldn't even notice a plug crapping out
That's the point of changing out before it craps out. Most don't know a plug is going bad until it's not firing. It's the trickle down affect, one cylinder that's not firing properly affects the next in the firing order. With the price of gas/ loss of gas mileage, new plugs are cheap insurance.
 
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