I replace mine in the spring.Any where from 12-15k mi. and check them a couple of times in the summer.Don't like to leave them in too long without cleaning the threads off and using anti-seize compound.I've heard too many horror stories of the heli-coils comming out with the plugs.

 

Haven't changed mine yet but then I only have 17k miles on them. I guess I don't understand why they have to be changed so often. You can run your car or truck plugs 100k miles. what's the difference between the two?

 

Yes this thread is 8 years old.

For the 2015's the manual states every 2 years or 30K miles which ever comes first. So Change them spark plugs when you are supposed to change the brake fluid.

 

Dealer changed mine at the 10K service on my 2016 Limited and it actually ran better!

I change the plug on my lawn mower every year and it has a lot fewer than 10k miles!

 

This is just like an oil thread. The difference between plugs and oil is there are shade tree ways to measure plug performance, but it takes a lab to test your oil. I see those who brag about NOT watching fuel mileage, and that is fine. However, fuel economy is a good indicator of combustion efficiency and so is spark plug tip color. When my mileage begins to drop spark plugs are cheap and easy to change. On my machine, I have never seen fuel economy drop in less than 30,000 on the plugs. A new plug makes a spark with less juice so when starting isn't as easy as it used to be, tired spark plugs are a good place to check. If it ain't broke, don't fix it. That can be a hard concept for some of the "fiddle happy, cheap insurance" guys, but to each his own. Don't know why people don't go to the manual FIRST, and then ask how that is working out for others. Harley would like you to eventually buy another machine from them, why not go with what is supposed to keep you a happy customer by following the manual?

 

I change my plugs when the body of the plug starts to rust, ...looks bad.

Never see a performance difference

Ken

 

every spring along with the air filter need it or not.

 

I replace the plugs on the Limited when the service manual calls for it, and each time the plugs were fine. You're not spending much on two spark plugs.

 

If they are lookin' good, and runnin' good, I clean 'em, swap 'em around, and run 'em.
Why mess up a good thing?

 

Being a tech all my life I let the plugs tell me when to change them. Look at the electrode, if its clean and has sharp edges, plug is good check gap and use. If electrodes are starting to round off a change is due soon. So people ride there bikes hard and some easier. This is what dictates the replacement time. A bike that is always rode hard rev to high rpm's they will burn out faster than a person who just cruises down the road. And another factor highway miles vs in town miles. All things to consider. when changing plugs, the recommended intervals the factory sets is to cover their asses when a bike is under warranty, loop hole to decline warranty coverage.