Thursday, November 14, 2013

How to Modify the Big Dog Mutt SuperTrapp Exhaust

In the last 17 years, Big Dog Motorcycles of Wichita, Kansas, has manufactured about 25,000 "factory custom" motorcycles. The Big Dog "Mutt" model, which has been discontinued, was one of the less expensive of these creations. The Mutt was 8 feet long, weighed 682 pounds and had a 117-cubic-inch S&S V-twin motor. Big Dog called it an "entry-level" model. Among numerous other custom features, the Mutt was delivered with a "tunable" exhaust manufactured by SuperTrapp Industries of Cleveland, Ohio. This is what you can do with the exhaust when you have a few minutes and a few tools.

Instructions

    1

    Remove the end cap from the SuperTrapp exhaust on the right side of your motorcycle by unscrewing the three Allen bolts with an Allen wrench, socket or key. Remove the disc assembly from your SuperTrapp exhaust.

    2

    Count the discs. A full set of SuperTrapp tuning discs is 18 discs. Your motorcycle probably has 12 discs.

    3

    Remove discs to increase back pressure, increase torque and decrease volume. Add discs to reduce back pressure, increase horsepower and increase volume.

    4

    Stack the discs and the end cap. Orient the discs so that the flat surface of the discs face inward into the exhaust and the outer lip angles away from the exhaust core.

    5

    Align the three screw holes in the stack. Insert the three screws through the end cap and disc stack. Apply SuperTrapp brand high temperature lubricant or its equivalent to the exposed threads of each screw.

    6

    Align the screws with the threaded inserts inside the muffler. Face the rear of the muffler. Tighten the screw at twelve oclock first, the screw at 8 oclock second and the screw at four oclock last.

    7

    Tighten each screw to 15 to 25 inch pounds of torque with an Allen socket and a torque wrench. Road test the motorcycle.


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