Straightening Bent Exhaust Flanges

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Written by Randy Fox (Randysgym)   
Monday, 02 March 2009

Introduction

Yamaha roadstar exhaust flange fix bent straighten
Exhaust Header, Showing Warped Flange

I went to remove my aftermarket exhaust pipes the other day, but they wouldn't come off. At first, everything looked normal:

  • The exhaust header-studs looked fine.
  • Those four, chrome, exhaust-flange nuts weren't rusty or visibly damaged. In fact, they were new this year.
  • The flange--that part that rattles around when the pipe is off--looked good to me.

Nevertheless, after easily removing the flange nuts, I simply could not coax the flange of either pipe off the header-studs. I wiggled; I prodded; I pulled; I angled; I even pried a little. Somehow, it seemed the exhaust-studs had become wedged tightly against the outer edge of both flange bolt-holes. It actually appeared that the exhaust-studs had become bent in a direction away from the center of the exhaust-port.

Ultimately, I decided to use a hammer and cold-chisel on the end of one exhaust-stud, to bend it back toward the center of its exhaust-port. This released the flange, and the pipe fell into my hands with relative ease. Of course, I was now committed to replacing the exhaust header studs, since I had just ruined one of them.

In any case, when I examined the previously flat, quarter-inch thick, solid steel exhaust flange, I could see it had been bowed to a very large degree. Then I knew what happened.

I remembered that the nuts went onto the studs much further than with the stock pipes (which have thicker flanges). I had dutifly torqued the nuts, which was something I hadn't done on pipes before. In other words, I followed the service manual specs instead of my 'feel.'

The thinner steel (true for most aftermarket exhaust flanges for the Road Star), combined with the fact that they are made from mild steel, meant that I should have used much less torque than Yamaha specifies.

In addition, because my flanges bent so far, they bent the exhaust-studs, too. In the end, I had to replace all the studs and un-warp (re-flatten) the flanges on my new pipes.

My exhaust flanges are not removable from the pipes, and no trustworthy muffler or machine shop was handy, so I did it myself. This article describes how I straightened my own exhaust header flanges and replaced my exhaust header studs.

Note: This article assumes you know how to normally remove and install the exhaust system, including how to remove the right-side floorboard for the front pipe. If not, refer to the Road Star Service Manual and/or the manufacturer's installation instructions for your exhaust system.

 



 
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