ZENOAH G20 Muffler Mods
There is a lot of exta HORSEPOWER available in your ZENOAH G20 if you go to the trouble to get it. All you have to do is reduce the back-pressure in the stock muffler! In order to make this happen, you will have to GUT OUT the muffler and add a massive exit pipe FYI: Zenoah G20, G23, and G26 all use the same exhaust bolt pattern. So you can interchange the mufflers.

Here is a photo sequence of how to get that "missing" horsepower.

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FIRST: Cut off the stinger as depicted in the photo below..

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Gut out the muffler is seen here. Grab that pipe in the middle with Channellocks and twist that pipe out. It takes some effort to get this out.

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Fit a 1" semi-curved (or a straight pipe) pipe like this. You don't have to use 1" pipe, but the bigger this pipe is the more power you'll get. The muffler actually turns into an "expansion chamber" and that is where the horsepower originates.

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Braze the pipe to the muffler, check for leaks, then buff the muffler for painting. This metal is fairly thin, so you can use MAPP gas instead of oxy/acetlene. You can get a MAPP gas rig at Home Depot for about $30.00

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PREPARE yourself for about a 700 RPM increase!You will be impressed at the new found power, and it will put a Zenoah G26 to shame. The muffler tone is deep and power-sounding. You can use any high-temp paint but I use epoxy paint as its heat and gas proof.

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You will be ASTONISHED at the difference, and the noise is minimal.

My G20 went from 8500 RPM on a 16x8 APC to 9200 RPM! That is better than a G26!