Silencer, experamenting

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K.i.p

K.i.p

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Nov 8, 2009
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I've started to do a little self education and experimentation with a silencer for my 40. This is the second revised version.

Really nice sound but a little loud and too free. I get a power drop- out ramping quickly to full throttle. I'm going to restrict the final exit a little bit. I noticed with my fingers covering the outlet to various amounts the sound drops right off and a the power drop-out issue resolves itself.

I hope to do a little modification work at the shop today. I know it's a little bit like re-inventing the wheel but I enjoy learning.
 

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Sign Guy

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Jan 19, 2010
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I packed the insulation around my collector like you did in photo #3 and the bike was really quiet, I loved it (sound-wise) for the few min I had it in there but there was such a loss of power that after I got around the block I yanked it back out.

Looks like you have quite the machining set up. Quite a bit more than a hand held drill and a hacksaw and grinder like me!
 
K.i.p

K.i.p

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I'm currently employed in a pretty high end machine shop and there are some side benefits to that. This is just a little fun government project so I'm actually working pretty fast and dirty when I get a second here or there. I'm still messing with this to see what I can learn and to find out how effective it might be.

My opinion as of right now is that I am working with too little surface area to get the results I am looking for. I'll probably still do some more tinkering and see where I end up.

Here are a few shots off my hard drive of actual "work" just for kicks.
 

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K.i.p

K.i.p

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The inner baffle came straight off a sketch pad. I turned it and drilled it on what ever lathe I could jump onto and then cross drilled it free hand on a drill press. I could have made it really nice but it's internal and not exactly authorized work!

I realized last night that by removing the end cap I actually defeated the baffle system in the stock muffler. I'm going to make a plate and tube today to replace the route normally created by the end cap before the gasses reach the silencer. No wonder it wasn't as quiet as I hoped. Interesting mental exercise.
 
K.i.p

K.i.p

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Thanks Stuart. I did some more work today and restored the exhaust circuit of the stock muffler. It is slightly modified but the path is pretty much the same as it is with an end cap installed. I used a short chunk of copper tubing I had on hand and drove it into the muffler baffle. Next I drilled some holes on the left to restore gas passage through the baffle. I made a plate out of sheet metal and brazed it onto the muffler thus creating the pathway normally provided by the end cap.

I have added some course steel wool between the muffler and silencer, and a light packing down the center. I think this is as good as is realistically possible with out restricting the motor too much. (Oddly enough my motor seems to thrive with a little back pressure but there is a threshold naturally).

The exhaust is now quiet enough to make the gearbox noise seem unbearable and sound can now be heard from the intake. I think the only further direction I could take towards stealth would be a breather box on the carb which frankly would just look too ugly.
 

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stuartracing

stuartracing

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Dec 9, 2008
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Hey brother, thats gotta be the trickest most thought out muffler I`ve seen so far, as far as a home made deal....Sweet.....
I bought the Supertrapp slip on peice from Summit and finally got it all dialed in from carb. to exh. tone and performance....
 
K.i.p

K.i.p

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Cool, I've been reading about those here. Sounds like a nice design.

Thanks for the kind words, it was a fun project. I will probably trim up some fresh cans to make a neat final version. Black paint?
 
K.i.p

K.i.p

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Well I think this is final revision and I am super pleased. I took my time and did some careful cutting and grinding on my cans. I was actually able to keep the full length of the outside can by slowly grinding the top free without harming the crimped edge.

I used some caulk as I doubled up the inside of the can (one inside the other). I cut up another can to make an additional third layer on the side walls. All seams where alternated.

I made the decision to give steel wool a shot at serving as the packing. I noticed the fiberglass had gotten soggy from fuel discharge. I figure the steel wool should drain off and not loose it's insulating abilities from moisture.
 

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K.i.p

K.i.p

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Nov 8, 2009
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My baffle tube has some more holes in it now to compensate for the inefficient location of the random holes. Having done a neater job with the cans I was able to use one clamp to secure it. I did a quick test run a few minutes ago and this set up is nice. I think I hit it. Worth the effort in my opinion.

*EDIT 4/4/10

Wow! I let my son take the bike out for a run and I got to listen for the first time roadside. This thing is quiet. The sound is best described as a tamed moped. More purr, less pop. Stealthy.
 

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G3R0N1M0

G3R0N1M0

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Jun 19, 2014
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Porterville, Ca
K.i.p said:
My baffle tube has some more holes in it now to compensate for the inefficient location of the random holes. Having done a neater job with the cans I was able to use one clamp to secure it. I did a quick test run a few minutes ago and this set up is nice. I think I hit it. Worth the effort in my opinion.

*EDIT 4/4/10

Wow! I let my son take the bike out for a run and I got to listen for the first time roadside. This thing is quiet. The sound is best described as a tamed moped. More purr, less pop. Stealthy.
Click to expand...
Would you make me one of these?
 
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