DIY Muffler for schmucks, cost: $0

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Tony01

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Nov 28, 2012
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How to make a DIY muffler if you're a schmuck with a water heater pipe straight pipe on your 4-stroke.

Bike was running great but SUPER FREAKIN LOUD!!! Family told me it needs to be quieter...

Step 0: You're a schmuck with a water heater straight pipe, and you want to put a muffler on it but are too lazy to drive anywhere and/or would rather spend the $7 on beer, so you decide to make your own can muffler.. cause you're a schmuck. Also, being a schmuck, you don't have any right tools for the job, such as a drill press, welder, and you deal with what you have.

Step 1: find a suitable can. Anything will do, mine was holding some PVC primer untouched for years.. BINGO!

Step 2: Measure can length and mark on pipe with a sharpie. Also mark half the length. This is where your plug will go.

Step 3: Find area required for holes. My exhaust ID was .670", which translates to .352 square inch, so I need around 25 .140" diameter holes on both sides of the plug to equal this area.

Step 4: Drill holes. Since this is a round surface and you're a schmuck without a drill press, not to mention you're too lazy in your schmuckiness to even remove the freakin pipe from the engine, you will need a SHORT, STUBBY DRILL to "spot" the holes before going in with your longer drill. Spot, then drill.

Step 5: Drill a bigger hole in the center, and plug it. Best is to use a round metal plug. I found a 1/2" round piece that was already the right length. If it is round, insert it and form the pipe around it with vice grips. Then JB weld is so there is no way gasses could pass through that section of pipe, without going out the holes.

Step 6: Cut, not drill, a large hole in the bottom of your can. You won't be able to drill it with the thin metal. If the other size of your can has a small enough cap, you can get away with not even using the cap, and just cutting the threads and forming them around your pipe.

Step 7: JB weld the heck out of the can and pipe, and let sit overnight.


Results: 30 miles of testing have shown this muffler sucks. It robs the engine of a significant amount of power compared to the straight pipe. I should have put more holes and/or used a bigger can. But I didn't wanna buy a coke for $.75 just to throw it away for the can. However, it does its job. My family did not even notice that it was my bike and not a lawnmower, and I rode by two cops who didn't so much as LOOK at me.

Conclusion: This thing works and will never fall off. So until I figure out exactly what I need to do to get the most out of my engine with the exhaust, this will do. Trying to find information on a multi-stage header and performance silencer for my Briggs 3.5hp.
 

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xseler

Well-Known Member
Apr 14, 2013
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I had the following set-up on my 2 cycle for a while -- regular copper flex line for a water heater with a 3/4" lawn tractor muffler screwed onto the end. Worked reasonably well. But as stated above, it was ugly as sin!

 

Tony01

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Nov 28, 2012
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Yep, it's flexible but not TOO flexible. Holds its shape, and solid when mounted on both sides.

In the pic above, you can mount it like that, but I would caution you on the plastic or rubber seals inside, they may burn with the exhaust temp.

I found one of those "universal" mufflers with the 3/4" pipe thread. They have 14 row of 6 holes approx 3mm diameter on the end side, assuming the same on the intake side. This translates to: (.118/2)^2*3.1415*14*6 = .919 square inch. 3/4" diameter is (.75/2)^2*3.14159 = .442 square inch. So the holes on either side of the baffle actually add up to more than double the input area, making that muffler very un-restrictive. Not like my junky muffler. Perhaps an upgrade is in order.
 

xseler

Well-Known Member
Apr 14, 2013
2,886
151
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OKC, OK
The plastic 'washer' was removed from the side closest to the manifold --- I left the one by the muffler. The heat was a non-issue at this point --- hot, but not hot enough.

I didn't do the math on this --- just used what I had for this exhaust version 'X'. I guess this could be called a $0 exhaust, since I didn't buy anything extra.....
 

Tony01

Well-Known Member
Nov 28, 2012
1,744
1,751
113
sf bay area
That's good to know. I might get another one, maybe longer. I cut both fittings off.. Maybe it was a mistake. I used a 1/2" pipe fitting sticking out one inch on the motor, cut slots in the copper and hose clamped it. It leaks though, cause there is black stuff on the intake.