modifying stock pipes
Road Captain
Joined: Feb 2009
Posts: 537
Likes: 1
From: Southern California
Don 't do it, they are set up to run on the lean side the way they are. If you punch holes in the baffles it will lean it out even more and may run hotter than you may like. This may lead to premature engine wear. Not to mention the blisters on your @ss 
. Just kidding. The best way to accomplish what you want is to replace the stock mufflers with another slip-on with about a 1.5" to a 1.75" baffle and a breather kit. This is more expensive than a drill bit, but you'll be happier in the end. 
. Just kidding. The best way to accomplish what you want is to replace the stock mufflers with another slip-on with about a 1.5" to a 1.75" baffle and a breather kit. This is more expensive than a drill bit, but you'll be happier in the end.
Seasoned HDF Member
Joined: Mar 2008
Posts: 9,384
Likes: 1,776
From: Central Texas
I knocked the freeze plugs out of my 2000 fxdwg exhaust about a month
after I bought it and I did not have to change anything. the only problem
that I had was the freeze plug in one of the mufflers did not blow out
so I had to remove the muffler to push it on out then put the muffler back
on. The sound was music to my ears! Onced the freeze plugs are removed
the mufflers become glass packs. You can knock them out with piece of steel
pipe, but I can't rember if I used 1/2 or 3/4 or 1 inch pipe. A piece of pipe
is a lot cheeper than a long drill bit or SE slip ons
after I bought it and I did not have to change anything. the only problem
that I had was the freeze plug in one of the mufflers did not blow out
so I had to remove the muffler to push it on out then put the muffler back
on. The sound was music to my ears! Onced the freeze plugs are removed
the mufflers become glass packs. You can knock them out with piece of steel
pipe, but I can't rember if I used 1/2 or 3/4 or 1 inch pipe. A piece of pipe
is a lot cheeper than a long drill bit or SE slip ons
Seasoned HDF Member
Joined: Mar 2008
Posts: 9,384
Likes: 1,776
From: Central Texas
I'll tell you what you should do, go to the dealership and pick up a set
of stock pull offs and knock out the baffels and see if you, like them or
not. The dealership should give you the stock mufflers or sell them to you
for a little to nothing
of stock pull offs and knock out the baffels and see if you, like them or
not. The dealership should give you the stock mufflers or sell them to you
for a little to nothing
Last edited by 6 gun; Mar 29, 2009 at 06:53 AM.
Seasoned HDF Member
Joined: Dec 2004
Posts: 11,068
Likes: 1,476
From: Texas! Ya mean there's someplace else?
Here's what I've found out -
1) If your bike is a later model with O2 sensors in the pipes, you can drill, knock, or replace the mufflers, and the computer will adjust the air/fuel mixture back to the stoichiometric ratio.
2) The computer (probably) won't make the adjustment if you go to completely open (drag) pipes, as the O2 sensors are too narrow a band.
3) If your bike is an earlier fuel injection model without O2 sensors, the computer module may or may not prevent an overlean mixture. Only way to know is to try it; if it starts popping and running like crap, you gotta do something to fix it - remap, download, PCIII,V, or whatever they're up to now, or whatever poison you choose to adjust the mixture.
4) If it's a carbed bike, slip the next larger size jets in. Run it and see if you like it.
5) If you have the dinero, a dyno run and adjustments by someone who knows what they're doing will work wonders.
6) Knocking/drilling out the plug makes the mufflers act similar to glass packs. On a Sportster the sound is akin to a XR750 dirt tracker. Most on here don't know what an XR750 is, let alone ever heard one. I like it, but to each his own. On a Twinkie or Evo Big Twin, I don't know what it sounds like.
I drilled the mufflers on my Nightster using a hole saw. Easier than knocking them out 'cause it can be done on the bike without damaging anything else. But more expensive 'cause you gotta have a hole saw and an extension.
You will not hurt your engine if you knock the plug out and ride it for a short time. If you then decide you don't like the sound, or if it sniffs, sneezes, pops, etc., then drop the mufflers and put a freeze plug back in the hole you made.
Choices ....
1) If your bike is a later model with O2 sensors in the pipes, you can drill, knock, or replace the mufflers, and the computer will adjust the air/fuel mixture back to the stoichiometric ratio.
2) The computer (probably) won't make the adjustment if you go to completely open (drag) pipes, as the O2 sensors are too narrow a band.
3) If your bike is an earlier fuel injection model without O2 sensors, the computer module may or may not prevent an overlean mixture. Only way to know is to try it; if it starts popping and running like crap, you gotta do something to fix it - remap, download, PCIII,V, or whatever they're up to now, or whatever poison you choose to adjust the mixture.
4) If it's a carbed bike, slip the next larger size jets in. Run it and see if you like it.
5) If you have the dinero, a dyno run and adjustments by someone who knows what they're doing will work wonders.
6) Knocking/drilling out the plug makes the mufflers act similar to glass packs. On a Sportster the sound is akin to a XR750 dirt tracker. Most on here don't know what an XR750 is, let alone ever heard one. I like it, but to each his own. On a Twinkie or Evo Big Twin, I don't know what it sounds like.
I drilled the mufflers on my Nightster using a hole saw. Easier than knocking them out 'cause it can be done on the bike without damaging anything else. But more expensive 'cause you gotta have a hole saw and an extension.
You will not hurt your engine if you knock the plug out and ride it for a short time. If you then decide you don't like the sound, or if it sniffs, sneezes, pops, etc., then drop the mufflers and put a freeze plug back in the hole you made.
Choices ....
Last edited by pococj; Mar 29, 2009 at 07:51 AM. Reason: 'Cuz I always wanted to be an editor!
Intermediate
Joined: Sep 2008
Posts: 45
Likes: 0
From: Layton,Utah
don 't do it, they are set up to run on the lean side the way they are. If you punch holes in the baffles it will lean it out even more and may run hotter than you may like. This may lead to premature engine wear. Not to mention the blisters on your @ss . Just kidding. The best way to accomplish what you want is to replace the stock mufflers with another slip-on with about a 1.5" to a 1.75" baffle and a breather kit. This is more expensive than a drill bit, but you'll be happier in the end. :d
. Just kidding. The best way to accomplish what you want is to replace the stock mufflers with another slip-on with about a 1.5" to a 1.75" baffle and a breather kit. This is more expensive than a drill bit, but you'll be happier in the end. :d
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Intermediate
Joined: Dec 2008
Posts: 38
Likes: 0
I JUST DID IT TO MY 08 SG.Imo it sounds a lot better,you need a 1/2" drill bit about 12" long and something to center it up with I used a piece of an old shovel handle.You just drill a slighly bigger hoe in the center of the handle and use it as a pilot the baffle is thin and dosn't take much effort can be done on the bike if you are careful.