How To Build a Custom Exhaust with Josh Allison

Hey everyone, it's Josh from American Metal Customs! Let's talk about exhaust pipes! Every bike has to have one (or two!), so let us talk about how to make an awesome custom setup for your build! Creativity and thinking outside the box are crucial and will set your build apart from the pack! Let's do this!

You can get exhaust kits from a lot of places, but I like to get mine from Biltwell. They have great bends and have everything you need to get it done.

The kit comes with the Panhead, Knucklehead, Shovelhead, and Evo flanges. Shown here is a Shovelhead flange.

This is the Panhead flange

Shown here is the Evo and Knuckle

The way you cut the pipe is significant. I use tape to make a nice straight line all the way around the pipe to follow with either a cutoff wheel or bandsaw to cut it.

After you make the cut, it's also important to use a hand reamer to clean all the cuts so that there is no loose material and to be sure each piece tightly fits.

This is what a basic hand reamer tool looks like. There are a lot of different tips you can get to be able to clean the inside of the different radii of pipes as well.

Another tool you can use is a die grinder, and there are many different bits you can get for this tool as well.

This is an example of the start of the exhaust on my Knuckle. You have to decide on the overall look, then piece by piece start cutting your bends and placing each piece in the correct order. I try and make sure my pieces fit tight, then I put 2 to 3 TIG tacks on the pieces to hold them together. It's essential to tack them and not fully weld them so if you need to make adjustments they can easily be cut apart.

These pics show a slip flange so that I can take the exhaust system apart. Always think about how it can come apart for installation and easy removal if you need to work on your bike.

This pic shows how with the right cuts and a little creativity you can come up with anything!

Always consider design flow and function. On bikes like Knuckles, Pans, Shovels, Evos, SX65O CB’S you can run straight pipes and then jet your carb and tune to make your bike run well....that’s what most guys do. You can always put in cone downs or some other restrictors, but you don’t have to. If you are doing exhausts for fuel-injected bikes like on most of the newer stuff, you need to add these restrictions. And don’t forget the easy stuff - make sure it clears the kicker arm, tranny, and oil lines. Forethought is very important!

Another pic of an example of clearance and design.

Make sure your fitment and tacks are clean and tight so that final welding is smooth and clean.

Now I final-weld my pieces together and grind the welds being careful not to undercut any of the welds.

This is how your final weld with a 50-grit grinder should look.

Now I use a blue dye called Dykem to spray on my piece. The dye will show me the highs and lows when finishing out my exhaust system. You can get it from McMaster-Carr.

This is how your piece should look when done.

I achieved this look by filling the pipe by hand after I have DyKem'd it. I file it until the blue is gone.

An example of the hand files I use.

With the exhaust complete, it's time to decide on the finish. You can paint it, chrome it, leave it raw, or in the case of this example, patina it.

Remember: Practice makes perfect and being creative separates your build from the pack! Have fun and make some loud pipes!


Josh Allison

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Comment with Chopcult (14)

Commented on 8-20-2018 At 07:43 pm

Awesome right up. Clean and straight forward. Is tig welding a must? I’m dogshit at it but I do have access to a mig with gas. Will that do the same job just require more grinding at the end?!

Commented on 8-21-2018 At 01:32 am

To maintain part together, you can use this nice tool:

And the same thing using a custom way:

Commented on 8-23-2018 At 09:18 am

How did you patina it ?

Commented on 8-23-2018 At 09:48 am

Very nice!

Commented on 8-23-2018 At 10:24 am

Thanks for this, this is inspiring! dope work

Commented on 8-23-2018 At 03:25 pm

You don't have to TIG weld it. You can use a MIG just have to make sure to control your heat the best you can then same finishing process!

Commented on 8-23-2018 At 03:59 pm

The Patina came from Surfin Chemical. Great Place for patinas! @Badtesticle

Commented on 8-23-2018 At 06:07 pm

Thanks for sharing your process! How much clearance do you need for oil lines, wiring, casing, etc.?

Commented on 8-23-2018 At 06:09 pm

AKAs Deburring tool...whirlybird....burr whip
Rotary file... burr..

Commented on 8-24-2018 At 06:58 pm

Awesome man!

Commented on 8-26-2018 At 05:04 am

Can this be used on a metric bike namely an 06 Yamaha Road Star?

Commented on 1-29-2019 At 11:32 pm

great write up and pics cheers

Commented on 6-22-2021 At 08:54 pm

What a fabulous article. I never would have thought to use dykem and a file, to get that flat, metal finished, look.. It looks like a continuous piece of tube. Good job.

It is obviously an old article, unearthed by the crash. CryBaby Cycles website is gone now and the pipe builder's kit is discontinued.

I bet the archives are filled with great articles like this one.

If, in the course of rebuilding the site, if they could be organized in some way.. By keyword or otherwise? That would probably breathe new life into interesting things that were heretofore buried and forgotten.

Commented on 6-23-2021 At 04:50 pm

Confab - I'll pass along your suggestions.

The build kit is still available, you can find it here,

CBC is on hold for a bit, but Josh is working on a new project that we will be showcasing here soon. You can follow him on IG in the meantime

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