Drilling the Cat = Photo Proof!
Grand HDF Member
Joined: Jan 2012
Posts: 4,459
Likes: 2,896
From: Oklahoma
A few intuitive (not an engineer) observations. Once the drill bit approximates the inside diameter of the pipe, flow is improved about as much as possible even if some cat material is left over. If you want a tuner for the many reasons usually given, fine. If the stock tune is OK, my guess is that until you get the engine light indicating lean mixture, the computer can adjust to its limit to keep mixture at the factory setting. Once the need for fuel exceeds the factory limit, the light comes on and the tune change is mandatory, not optional. Lastly, wish I had the difference between the price of a drill bit and the price of a new header to just toss at my scooter. If something gets destroyed along the way, then replacement becomes mandatory, but why not try the least expensive way first?
Road Warrior
Joined: Oct 2010
Posts: 1,862
Likes: 127
From: Republic of Texas
A few intuitive (not an engineer) observations. Once the drill bit approximates the inside diameter of the pipe, flow is improved about as much as possible even if some cat material is left over. If you want a tuner for the many reasons usually given, fine. If the stock tune is OK, my guess is that until you get the engine light indicating lean mixture, the computer can adjust to its limit to keep mixture at the factory setting. Once the need for fuel exceeds the factory limit, the light comes on and the tune change is mandatory, not optional. Lastly, wish I had the difference between the price of a drill bit and the price of a new header to just toss at my scooter. If something gets destroyed along the way, then replacement becomes mandatory, but why not try the least expensive way first?
Advanced
Joined: Apr 2011
Posts: 58
Likes: 0
From: Greenfield, MN
Originally Posted by Lowcountry Joe
The best way to get rid of the cat material .buy a header with a superior design.
Seems like everyone has an opinion but no data to back up it... either way.
It would be nice to see some dyno numbers of an aftermarket system sproperly tuned compared to a cat-less stock pipe also properly tuned.
I'm guessing we won't see anything like that anytime soon.
The best way to get rid of the cat material .buy a header with a superior design.
Seems like everyone has an opinion but no data to back up it... either way.
It would be nice to see some dyno numbers of an aftermarket system sproperly tuned compared to a cat-less stock pipe also properly tuned.
I'm guessing we won't see anything like that anytime soon.
Road Warrior
Joined: Oct 2010
Posts: 1,862
Likes: 127
From: Republic of Texas
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Outstanding HDF Member
Joined: Dec 2007
Posts: 2,403
Likes: 20
From: Indy
I solved that problem in the ones I did , by tig welding them together with stainless rod, it still could rust where the chrome is burnt but what are you going to do?
Road Warrior
Joined: Aug 2008
Posts: 1,784
Likes: 92
From: Michigan
Looks pretty good! I would still do it the right way as far as de-catting goes.
Speaking of Xied's been their done that on my 08 and it was the biggest waste of money to date. Popped on de-cell and thru codes, took them off and all was good again.
Speaking of Xied's been their done that on my 08 and it was the biggest waste of money to date. Popped on de-cell and thru codes, took them off and all was good again.