My manual says to inspect them every 5k and replace 20k which I do. Here's a handy cross reference.

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

 

That's asinine.

Not even any comparison. Period.

When was the last time a spark plug failed?

I'm not against changing them every 20k... 10k... 5k... it's a $12 / 5 minute job....
....but tell me the last time you heard of a spark plug failing.

A clogged air filter absolutely robs performance.

A flat tire... you may be the guy I have to explain that one to, but for now, I won't.

 

Does every thread here need to turn into a "you're stupider than me" thing?

 

I just installed NGK Iridium plugs and don't plan to ever change them. Supposedly they're good for 100,000 miles, which means they'll outlast me. lol

 

Just did mine at 18K and they still looked great but were not tight.

 

I had a set of factory plugs go out at 13,000 miles on my Road King.. I just turned 16,000 on my Road Glide and installed Iridium plugs and 10.4 MM Wires...

 

Whether you change them or not, you need to pull them out and inspect them. Not so much to see if the plug is OK, but to make sure you can actually pull them. Aluminum and steel don't like touching, and over time will seize. So you need to pull them once in a while, and put a dab of copper anti-seize on them.

And I give a +1 to LP's question.

 

I think you missed the sarcasm in his post.

 

Everyone missed the sarcasm in mine.

 

But what about the pulstar plugs? lol