Last summer I switched to Autolite 4163, one heat range colder than stock, and have been running them ever since. Stock is 4164. No problems at all and the ion-discharge knock sensor appears to be working properly with these plugs. These were much cheaper than the HD-branded plugs, and be purchased at Auto Zone and other auto-parts franchises. Other good brands include Denso, NGK, etc.

 

http://www.harley-performance.com/ha...park-plug.html

 

when time came to change the stock plugs in my 2006 roadglide, I bought the HD gold plugs. for some reason my bike didn't seem to like them. harder starting, and seemed sluggish. switched them out to Denso Iridiums 2 days ago and so far bike runs better than ever. I know some will say it's all in my head but I don't think so.

 

my ultra has Accel's and the Ironhead has NGK. Both work just fine for me.

 

IMHO, by not using HD plugs, you could mess up your knock sensor. The Delphi ECM detects knock using an ionization method.

"A small voltage is applied across the plug electrodes during while the power and exhaust phases of the cylinder are in progress." Ref: Adam Wade Motorcycle Fuel injection pp. 61

I'm not sure if substitute plugs will have the same resistance values as the HD plugs.

Gary

 

No you can use any brand you want just make sure it is the correct heat range.
That said the standaed HD plugs are fine.
those fancy 2 or 3 times the cost Platium plated extra specila BS plugs do nothing more than last a bit longer and if you change your plugs as you should there is no reason to use them.
Other than it may make you feel good.
NO spark plugs with 4 contacts do not burn fuel better and indexing is a joke