**Cooler Plug**

Discussion in 'Touring Models' started by skizman, Feb 16, 2014.

  1. skizman

    skizman Active Member

    Hey. I put fishtail pipes with shorty baffles on my 02 Road King, but noticed the rear cylinder is running a tiny bit hotter than the front. The plugs that I'm using are
    NGK DCPR7E. I went to a few auto parts stores and seemed they couldn't come up with a cooler plug.
    I tried ice cubes but they don't last very long.:small3d031:
    Any ideas?
  2. btsom

    btsom Active Member

    The NGK web site will tell you how to decode the heat range notation. I don't remember if NGK uses bigger numbers for hotter plugs or the reverse. That will tell you what plug to ask for. Spark plug heat range is important for keeping the plug clean without damaging other components. A cooler plug won't lower the operating temperature of the rear jug, that is a mixture/cooling situation. The rear jug is shielded by the front jug and receives heated air flow which has already cooled the front jug so it is bound to run a bit hotter. Does the current plug show evidence of overheating or is this a leg comfort thing?
  3. Jack Klarich

    Jack Klarich Expert Member

  4. skizman

    skizman Active Member

    Thanks for the NGK site...real good info there and learned that cooler plugs have higher numbers. Mine are 7, so maybe that's already the coolest plug.

    My new plugs actually look like my old plugs...front cylinder plug was a light tan color, and rear plug was a white/light tan, so you are right btsom....rear cylinder runs a little hotter naturally.
    I will call NGK just to hear their comments.
    Thank you!