How To Build A Custom Motorcycle Exhaust

New Pipes For The Mad Dog's Black Widow

This was originally written by McGoo from Biltwell. It was posted here with his permission, and is a nice tutorial on how to use the Biltwell Builder Motorcycle Exhaust Pipe Kit to make a killer custom motorcycle exhaust for your chopper, bobber, tracker, custom Harley Sportster, Triumph motorcycle, etc. You can use this same tutorial with many different choices of exhaust fabrication pieces we have available on our website.

BMX kingpin Chris "The Mad Dog" Moeller at S&M BMX solicited my help to make some new pipes for this infamous Black Widow. S&M BMX builds their own high-dollar BMX bikes in their own building right here in the US of A, so we had skills (shop manager Jason Balls, himself a chopper freak of some repute) and equipment at our disposal. Chris and I are old BMX grease monkeys, but we put our heads together and dreamed up a pipe set for his new motor in a matter of hours using only a Sharpie, a piece of welding rod and our (half) wits. Here's the blow-by-blow from last night's shop session:

Step 1: Prep your work area

Step 2: Make your rough drawing

Step 3: Create your basic shape with a piece of welding rod

Step 4:Install your header flange and start picking your bends

Step 5: Tack your little bends and straights into shape

Step 6: Assess your progress by installing and reinstalling your pipe as it grows

Step 7: If you like where things are headed and and everything is clearing what it's supposed to, do some 1/2" long root welds to hold your sub-assembly more firmly into place

Step 8: With front half of pipe in limbo, assess your design and method of mounting in the rear. Mad Dog didn't like the way his cocktail shaker mufflers hung on a giant bracket, so he jettisoned this contraption in favor of some tabs. Yes, those are zip ties Jason is staring at.

Step 9: Clean up your tube surfaces with a flap disk to make room for new steel mounting tabs and new welds

Step 10: Using your pipe sub-assembly as a guide and a jig, determine the location
of your support tabs and tack them into place

Step 11: Finish weld your pipe

Step 12: Admire your handwork. Repeat for the rear cylinder

Random stuff we learned along the way:

Not even the clean cut of a bandsaw will leave your tube openings in perfect shape for end-to-end welding.

When this is the case, massage the tube openings with sandpaper. The more horsepower, the better

The pipe for the front cylinder took us a little over 5 hours to build, and required some mods to the footpeg and foot controls location, and the aforementioned mods to the muffler mounting. We measured three times. cut twice and welded once on every joint. It's better to whittle away a little bit of tube at a time to get your joints perfect than it is to whack off too much tube... taking off is always easier than adding on, especially on tight radii.

Beer actually made this project go faster.

If you're a badass TIG welder like Jason is, you can fuse these tubes together without rod. He did this several times and it looked awesome.

As the three of us proved, anyone with average talent, simple tools and some spare time can make pipes for their bike—you don't need a multi-million dollar bicycle factory at your disposal to do it!

Thanks to Chris for inviting me to his party, and to Jason for being such a good workmate.

I can't wait to see the rear pipe. Good luck and have fun, Mad Dog…

A great piece of advice from Derrick: "For all you tig-tackers, try using some hose clamps with holes drilled in it to hold your place while you tack. trust me, it makes a world of difference in time when fitting and welding a set together."

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