This guide will show how to remove the old spark plugs, check the new spark plugs for installation, prepare the spark plugs for installation, and reinstall the new spark plugs.


The spark plugs are easy to spot on the left side of the motorcycle.
  • The spark plugs are easy to spot on the left side of the motorcycle.

  • The procedure for removing the spark plugs is the same for both the front and back cylinder, and either spark plug can be replaced first. This guide will show how to remove and install the spark plug in the rear cylinder.

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Carefully remove the spark plug wire. Do not pull on just the wire, squeeze the spark plug boot, and pull it together with the wire.
  • Carefully remove the spark plug wire. Do not pull on just the wire, squeeze the spark plug boot, and pull it together with the wire.

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  • Use an 11/16" spark plug socket to unscrew the spark plug by turning in a counter-clockwise direction.

    • Some aftermarket spark plugs that fit the Sportster use a slightly larger 18mm spark plug socket.

  • Remove the spark plug from the cylinder.

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  • Always inspect your new spark plugs before installing. Check the gap on your replacement spark plugs with a feeler gauge. It should be set to .040 inches.

  • If they are not pre-installed, make sure that the crush washer and terminal nut are installed.

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  • Using your fingers, install the new spark plug into the socket, and hand tighten until firm.

  • Using a torque wrench, tighten the spark plug to the proper specification.

    • When installing spark plugs, proper torque can be important. To loose and they could rattle out or leak; too tight and you can strip your cylinder head. The correct torque for this plug is between 90 and 120 inch lbs.

Questions.1 with a stage 1,2 or 3 would you agree a wider gap? 2nd question which is simular to first.i do run my motor a little rich.rather rich than lean.my question is with modification on a harley davidson sportster.what do ou recommend.so many choices from om to iridium to platinum.then the gap and also are you a believer in cutting the eledtrode approx half off for max combustion.how much would you recommend cutting and back to og question.the gap.is a larger gap.capable of power increase.since ive tried both i swear i feel a power increase.but is it anticipated or other varibles???you opinion is valued.

Joey zero - Ответить

  • Reinstall your spark plug wire by pushing it firmly onto the new plug.

  • Make sure that it seats properly. You can usually feel a definitive click when it is installed correctly.

I have a Harley Davidson Xr1200x Sportster which I just got. Changed the oil also tranny & filter as I couldn't find last date of service coang of oil. So yesterday I checked the spark plugs they were clean. But the mechanic cleaned them & said the needed gap them as one was too narrow. Mind you I had no issues at all. Gapped them at 0.40 now I'm not getting the same smooth sound or feel as if it's miss firing. I have iridium spark plugs okn my bike should I change them to NGK or get another set of iridium spark plugs.please advise..

Steven Sewell - Ответить


Be sure to repeat the above procedure for the remaining cylinder.

13 участников успешно повторили данное руководство.

Eric Essen

Участник с: 04.06.2010

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Just for information, particularly in the UK, you may be able to purchase sparking plugs cheaper at a Chandlers, as there are quite a few 4-stroke outboard engines use these plugs.

BigRoj - Ответить

How do you do this with a XL1200S with dual spark plug heads??

Andy - Ответить

Couldn't have made it any simpler

Matt Pramik - Ответить


- appreciated

Thank you so much for your posting. I'm 2k miles from my daughter who is teaching herself how to maintain her own bike. You site is immensely helpful and appreciated as much.

mrjacecabezut - Ответить

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