I bought them at the hardware store they are "test plugs" for pipes. I had to safety wire them, but it worked well. Just put them in the pipe, cinch them down, then tie then in. A cork would work too.
Before the first freeze. The plugs popped out with this arrangement before the metal moved.
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First or second run with the ends tied. Really making progress.
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Final result, not perfect but way better than we started. This is an Akrapovic full system from a 2010 Aprilia Mille.
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