I was looking at a couple of old posts, came across a comment about modifying a Thunder Header. What are the pros and cons? How is it done? After it's done, does the mod cause a re-tune (DYNO)? last but not least is it worth the time and effort?

 

imo the theader is a great put it on and tune the bike... any time you alter the air flow in or out the afr should be checked. just to be safe.

 

It's a simple mod that doesn't require any AFR tuning after it's done.

What you are modifying is the rear most part of the baffle. If you look into the muffler from the rear, you will see a square made out of metal. What you do is take a long socket extension or steel bar and bend 3 of the 4 sides of that square out towards the round sides until it is about 1/8" away. What that will do is create a bit more back pressure and take care of the low-end torque dip the TH is known to have.

I did it to both of my TH exhausts when I had them, and to a couple of friends as well.

Steve

 

Thank you George and Steve, as always I appriciate the help.