Quiet Needed!! Loud expansion chamber PIPE

Pablo

Master Bike Builder & Forum Sponsor
Dec 28, 2007
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You guys probably saw this post coming 5 miles out....or rather you heard me coming :bike:

I installed a Pocket Bike expansion chamber this weekend.

I'm done gushing about my new power (it's still amazing), now the reality of the new expansion chamber is setting in……this sucker is LOUD. I wouldn't mind if I lived in the country - but I'm afraid the neighbors will start griping. Sorta .226 machine gun fire - crack-crack-crack - slow idle is nice though. (Added beni, it even idles better than originally, surprisingly I had to back the idle screw off quite a bit) When idling it is not on the pipe - just flowing through, so to speak.

The source of this exhaust noise appears to be twofold. Per my ear nearby, part of it is my fittings up front - they are fairly loose. I can easily take it apart. Maybe expand the male half to make snug slip fit, on the male (steel) manifold I can use some exhaust system sealant goop, because that stubby steel flanged nipple could be tough.

The other is the so called silencer (it should be called a loudener) - it's not removable (welded to the pipe after the chamber itself). The silencer "cover" is riveted in place. To improve this one could be interesting. Drill out the rivets and stuff it? (I think it's empty inside). OR cut it off and attach an new quiet one?? Where is a silencer source? What will be left to clamp onto will be about 1" of or so 5/8"-7/8" OD stub. (I need to measure it)

I guess I'm open to any ideas as well as help finding a new silencer.

Thanks!

P
 

spad4me

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Jan 20, 2008
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A chamber in resonance is extremely loud HUH.

Stuff aluminum screen material in the silencer after you remove the rivets. then use screws to seal.
If your pipe to the chamber is leaky expand the ends of the tubes by hammering in a tapered plug, then a trial fit.
Lather , Rinse, Repeat.
 

Pablo

Master Bike Builder & Forum Sponsor
Dec 28, 2007
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A chamber in resonance is extremely loud HUH.

Stuff aluminum screen material in the silencer after you remove the rivets. then use screws to seal.
If your pipe to the chamber is leaky expand the ends of the tubes by hammering in a tapered plug, then a trial fit.
Lather , Rinse, Repeat.
A little louder I expected. Aluminum screen material? Interesting idea. I was thinking steel wool or fiberglass batting.

No need to hammer - I have a 20 ton press. :D
 

spad4me

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Jan 20, 2008
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A little louder I expected. Aluminum screen material? Interesting idea. I was thinking steel wool or fiberglass batting.

No need to hammer - I have a 20 ton press. :D
I use aluminum screen in my homemade mousecan style muffler.
I did NOT like the POP POP POP. when I cut off my baffle.

I got a nice power increase and a pleasant rumbly sound.

I used a 1,5 to 2 inch exhaust pipe 45 degee I think,
Stuffed with aluminum screen material.
A length of plumbers tape and a 2 inch 14-20 bolt hold the end of the pipe and keep the screen in.
You are going to use a 20 ton press for finish work?
 
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Pablo

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Dec 28, 2007
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Sweet! Yeah that pop-pop-pop gets old real fast. It's not so bad at 40 mph, but.......I'm sure it is to observers.

I'll need to get some real Al screen. All I have is fake new age kind. That would melt and get nasty.
 

spad4me

New Member
Jan 20, 2008
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Sweet! Yeah that pop-pop-pop gets old real fast. It's not so bad at 40 mph, but.......I'm sure it is to observers.

I'll need to get some real Al screen. All I have is fake new age kind. That would melt and get nasty.
When I top out the only thing I can hear is the air rushing past my ears.
 

Ilikeabikea

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Jan 27, 2008
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Norman makes some awesome silencers. He presses out some cups and rolls a tube and sticks them in it. Maybe we can take some pictures or maybe he can tell you how he does it. It really quietens it down. Just ask Cruiser......................
 

Ilikeabikea

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We just got back from a ride. I bet he'll be on here in a minute. Or we are fixing to go eat. So it might be a little later. But if you can weld you won't have any trouble building one.................
 

Pablo

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Dec 28, 2007
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I took the entire pipe off and drilled the cover off the silencer, removed the tiny amount of glass packing and filled it with steel wool....unrolled the pad and rolled it around the holey pipe (one pad fit perfect!). Used a couple screws to put it back together (didn't have enough of the right size)....trial run :D Also I measured the pipe sizes and stuff for future ideas.

Then I expanded the copper fittings on the header side, cleaned them up and put them tightly together with some exhaust system sealant goop.

Oh also I raised my bracket up a bit to bring the pipe up. Looks like I "wanna go pro" rotfl

Lastly I put a 1/2 copper elbow on the output pointing down - to muffle and reflect the sound down rather than straight out. The fitting fit nice and tight.

Will try it today as sealant goop is best dried overnight.
 

Saddletramp1200

Custom MB Buiilder
May 7, 2008
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If they start whining tell them that your performing a Valueable community servicerotfl Your scaring away those terrible birds thay do do on their cars!
That will shut em' up for a while. Tramp(c)
 

Pablo

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Dec 28, 2007
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OK I'm back. For sure it is much more quiet. I could use it a bit more quiet, but it sounds nice and it doesn't seem like I sacrificed any power. It's probably the same dB as stock, but just sounds more civilized. Later I will go for more cone of silence.

I was doing over 30 in 3rd gear with absolutely no effort. 4th, 5th, 6th remain uncharted territory in my hood.
 

Pablo

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Dec 28, 2007
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I did the cut silicone hose thing in the cooling fins - pretty surprised that it made a difference. All my noise is now out the exhaust - so tomorrow I'll be doin' some plumbing. First I just extend the stinger and put the 90° on.
 

Saddletramp1200

Custom MB Buiilder
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You would think with the tiny amount of oil a 2 stroke spitts into the pipe the darn thing would never rust. But they do. I had a pipe with so many holes in it that it looked like something Cher would wear on stage. LOL Tramp