teabowl13 wrote on 07/24/12 at 19:58:46:HEY GREG,
Just curious, I'm sure the hole in the middle of the plug gave you a louder sound, but did you notice a serious change in the performance of the bike after you drilled it out?
Seems to me if that plug is so cheap and easy to re-install it would be easy to play around with a variety of holes and sizes etc. Might make the Harley pipes somewhat tune-able, which would be quite something!
If that's a 1.5" plug, I'm guessing it's a 1" pipe you're using? or 1.25"?
It was louder and deeper. If there was a performance gain or loss, I didn't notice. I just popped it out again to measure. The plug is 1.25" in diameter and my piece of pipe is 1" in diameter. They are tune-able for noise. Tune-able for performance? YMMV. I drilled different size holes, starting small, until I got a sound I liked. I would guess that the plugs aren't supposed to be removed/re-installed as many times as I have done it, but it hasn't shifted on me yet.