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How to Modify the Big Dog Supertrapp Exhaust

The SuperTrapp exhaust on many Big Dog motorcycles is a tunable exhaust. Most motorcycle exhausts use baffle tubes and chambers to modify the exhaust stream. The baffles make the exhaust change direction and slow down. Slower exhaust is quieter because the exhaust stream contacts high frequency absorbing packing materials longer. SuperTrapp exhausts modify the last stage of exhaust flow with tuning discs. The gap between the discs is smaller on the inside than the outside. The idea is to create expansion chambers with the discs which increases what is usually called the "scavenging effect" of an exhaust system on engine exhaust. This is how to replace and tune all modifiable parts in a SuperTrapp two into one exhaust.

Instructions

1

Loosen and remove the three end cap Allen screws from the end of the exhaust with an Allen socket and socket wrench. Remove the end cap and disc stack.

2

Remove and keep handy the two Allen screws on the bottom of the exhaust outlet. Remove the SuperTrapp core assembly from the muffler body.

3

Slide the replacement core assembly into the muffler shell. Align the screw holes in the new core with the screw hole in the muffler shell.

4

Secure the new core in the muffler shell by reinstalling the two Allen screws with an Allen socket and wrench. Tighten the screws to 20 inch- pounds of torque with the Allen socket and a torque wrench.

5

Count the stackable discs in your disc stack assembly. Your exhaust may contain as many as 20 discs or as few as 12. SuperTrapp suggests you experiment with different numbers of discs until your engine finds its "sweet spot."

6

Stack the discs you decide to use inside the muffler end cap. The flat surface of the discs should face the core assembly.

7

Apply SuperTrapp brand high temperature lubricant or its equivalent to the Allen screw threads. Replace the end cap and disc assembly in the end of the muffler.

8

Tighten the Allen screws to 20 inch-pounds of torque with the Allen socket and a torque wrench. Test the performance of your motorcycle on the road.