Silence my bike

Discussion in 'Motorized Bicycle General Discussion' started by targetdg15, May 24, 2010.

  1. targetdg15

    targetdg15 New Member

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    How can I make my moped super silent?
     
  2. Gareth

    Gareth New Member

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    Pour some fine silicate into the gas tank. It should lock the engine up nice and seized like. After that, all will be blessedly silent.
     
  3. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    Sugar's cheaper. Actually, if you never start it, it shouldn't make any noise at all. You could just pedal. Or coast. That's probably as quiet as you can get.
     
  4. AZMotorbiker

    AZMotorbiker New Member

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    The latter is what worked for me when I left my condo complex this morning. I pedaled until I was at the entrance to our complex by the main road, then I fired 'er up and off I went. I can make all the noise I want out there. Besides, half the fun of these little bikes is makin' noise. :D

    In all seriousness, if quiet is what you're after, convert it to electric. It doesn't get much quieter than that unless you power it yourself with the pedals.

    -AZ
     
  5. taddthewadd

    taddthewadd New Member

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    What about you guys with 4 stroke engines? Are they quieter than the 2 strokes?
     
  6. Cabinfever1977

    Cabinfever1977 New Member

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    If there legal in your state,why worry about being quiet, aslong as you have a muffler.
    Cut a small silicon or rubber hose into small pieces,place 1 piece between every fin on engine icluding head,cover clutch cover with a mouse pad or rubber sheet,glue on,inside or out side. Add second muffler on the end of your first one, make sure muffler gasket is not wore out and replace as needed. Make a air box to hook to your air cleaner as half the noise comes from your intake.
     
  7. BarelyAWake

    BarelyAWake New Member

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    Cabinfever has some good suggestions!

    I like a quiet bike if for no other reason than so I can hear myself think lol

    It's true that many like the screaming death noises - equating decibels with speed, it amazes me how many will stick a supertrapp on the back of their Ford Escort - Mario Andretti in an economy car right?

    Still, to each their own and it's also true that in the quest for top performance often mufflers are the first to get sacrificed. With good reason, most mufflers are insanely restrictive, much like trying to run a marathon breathing through a drinking straw. Drilling holes & pulling endcaps seems to help, but with two strokes it really doesn't, not as much as it seems anyway - it's mostly a placebo effect as a screaming engine has just got to be fast lol Unfortunately, just sticking an additional muffler on the end of your exhaust will make that drinking straw even smaller.

    One easy way to reduce exhaust noise is to simply increase the length of the exhaust system. While length does increase back pressure, it's marginal and well worth it if you're after quiet. Not only does it help reduce the noise - it puts it behind you where it's far less annoying... for the rider anyway heh, a simple solution would be the "poo-poo" pipe sold by some of our vendors... but it still has the stock muffler on it and the generic (if longer) headpipe..

    [​IMG]

    Two strokes need some back pressure to run properly, they need tuned back pressure for performance - problem is most expansion chambers go with the "louder must be better" theory and that can get annoying - but easily fixed. Of the available expansion chambers most don't have any silencing at all, but some do and the best for performance and noise reduction both have a glasspack silencer on the end.

    [​IMG]

    As you can see from the pic, there's no baffles, no screens or plates - the exhaust can freely flow through the inner pipe as the fiberglass sound insulation absorbs some of the shock wave, deadening the "bang" much like a gun silencer. The only downside is the fiberglass batting will load up with carbon and unburned oil in time, needing to be repacked periodically. Not really a big problem though as regular old household insulation fiberglass will do just fine and it's usually only four pop-rivets or screws to get it apart.

    I took the SBP's expansion chamber exhaust and doubled the length of it's glasspack silencer, it's now just a little quieter than stock at half throttle or less - it wakes up and gets louder only at WOT, which is exactly how I like it lol;

    [​IMG]

    It would help to reduce the noise even more (and even maybe a tiny bit more power) if I wrapped the headpipe and chamber with Header Wrap... but I've not gotten to that yet lol, it's on the "to do" list tho heh

    As Cabinfever mentioned, another way to help reduce noise is the oft-forgotten intake end, for more ranting about that - check this thread: http://motorbicycling.com/f4/remote-airbox-intake-silencing-cheap-10967.html
     
    #7 BarelyAWake, May 25, 2010
    Last edited: May 25, 2010
  8. Happy Jack

    Happy Jack New Member

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    #1 Reason to "be quieter" is that loud pipes give the Law "probable cause" to pull you over. Probable cause may then cascade to other more serious charges on you. Yes, loud pipes even with a muffler can (and often are) violation of "nuisance ordinances" and when you eventually confront a Judge or jury , they could frown on you for disturbing their peace.
     
    #8 Happy Jack, May 25, 2010
    Last edited: Jun 7, 2010
  9. K.i.p

    K.i.p New Member

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  10. Dan

    Dan Staff
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    Kip, that is uber cool. Nice job.
     
  11. targetdg15

    targetdg15 New Member

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    Well one of the odd jobs I do is paper delivery. I want a silent engine so im not waking up my customers...it tends to lower tips :)
     
  12. Dan

    Dan Staff
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    LOL, I bet. Not only tips but folks will start throwing stuff.

    Really good advice so far.

    Ever see/hear a fork lift? They have huge mufflers and ya can barley hear them. Could put a large repository sort of thing at the exhaust end. I have experimented with radiator hose as piping. Before the actual muffler, gives you a thump-thump sound (really, really cool sound) but melts if to close to the engine. After the muffler, dampens sound great but I have yet to run it into a larger muffler that would silence it all together (almost and so far just in theory) and not add any restriction. Really did get the idea from fork lifts.

    The goal being the exhaust get out of the way of the next stroke as fast and smooth as possible then breaking up the sound waves before releasing sort of deal.

    Also elsewhere, I forget who, built a silencer thing for the air intake. Some noise does escape from there but I dunno if it would be worth it for you.

    Just my thunks on this. If ever I get around to finishing the "Mega-Muffler' will post. Should work but I always think that, snork.

    Pleas post what ever you try. This question comes up a lot and you will be helping lots of folks.

    .flg.
     
  13. Happy Jack

    Happy Jack New Member

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    Nice work. Going to sell some? Be good as a put-on & take-off as a quickchange when needed.

    Side note: I heard a lecture once from some engineers at the highway dept. They were trying to quiet the road noise from a new highway. One thing that struck me informative: the exhaust pipes do act like a musical instrument in a way. The direction you point the tip of the exhaust is just like pointing the mouth of a trumpet.

    The ATV guys are really trying to get a "silencer" for their woodsie stealth.
    Popular one is the KOLPIN exhaust.
    Looks like it may work similar to forklift after-muffler.
    KolpinĀ® ATV Stealth Exhaust System? - Quiet Like You?ve Never Heard
    [​IMG]
     
  14. taddthewadd

    taddthewadd New Member

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    When I used to fly remote controlled airplanes I experimented with the muffler. The engine was a two stroke with a muffler. I put a piece of silicone tubing (used on the plane for fuel tubing) on the tip of the muffler. The tubing was about 1.5" long. It reduced the noise by more than half. So much so that I couldn't believe it. Maybe try experimenting with tubing on the tip of the muffler.
     
  15. Dan

    Dan Staff
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    Very cool Tadd! They sell exhaust hose. Am still looking. I saved it some where but it was too small dia.

    Vetus Denouden Rubber Exhaust Hose Rubber Exhaust Hose 3-1/2" - SLANG90 - BoatersWorld.com

    West Marine


    Glad you brought this up again. I had to put a muffler on my HF and lost 5MPH. Thinking I can regain it useing "soft" pipe as a sort of expansion chamber. Com-on payday! lol

    Funny thing about my 4 smoker, it ran and sounded great with just the header. Not a bit of pipe or muffler and no back pressure to speak of. Just a slight curve in the three inch long manifold. Loud but had a great sound.
     
  16. Dan

    Dan Staff
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    OH, is also really important not to point towards the road or down. It echoes in a way. Emergency vehicles use this effect and place sirens low so the sound "skips" like a flat stone on a pond.

    This thread is really getting interesting. I can't wait to see what every body comes up with.
     
  17. BarelyAWake

    BarelyAWake New Member

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    That was prolly lil ol' me Dan :D Remote Intake

    [​IMG]

    While I did build it with better filtering in mind (dusty/mucky off-road use) it did actually serve to help quiet the engine noticeably - at WOT in particular. Intake silencers are actually fairly common on 2 stroke ultralight engines, more common than ya might think even on 2 stroke dirtbikes, ATVs, snowmobiles, etc. as the airbox is often designed as a silencer as well.

    Granted - an airbox alone wont turn yer screamin' 2smoker into a stealth mobile, but it's the cumulative effect of all the above mods that gets ya there ;)
     
  18. silverbear

    silverbear The Boy Who Never Grew Up

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    Interesting thread. One more benefit to a quieter exhaust is you would be able to hear if something suddenly changes elsewhere on the bike... a rubbing sound, screech or other indicator something's not right. I also don't like disturbing everything in the forest when I ride. The quieter I am the more I see in deer and bear and such. A little noise is good to announce your presence, but too much is really offensive to all including myself. I'll be following this one to see if there are simple fixes. I'm going to try the rubber hose deal after the silencer to see what effect it has. Somebody is going to come up with something super low tech. Gotta love this forum. You guys are the best!
    SB
     
  19. Dan

    Dan Staff
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    Very cool guys and good points. Had a thought last night and is prolly one of those things I will never get around to but a "Y" in the pipe. One going to a really stealthy muffler and one st8 pipe. So could scream fast when needed and run silent, run deep when necessary. Spring loaded to run at your preference and remote controlled via a locking clutch handle. A lil involved but easily done. Once again I am sure I am over complicating but seems to be a hobby of mine, snork.

    Took the cover off my HF air cleaner and replaced with chicken wire. Looks funky but did add 200 RPM.

    This really is one of the best parts of motorized bicycle riding. Tinkering, plotting an' scheming. If it weren't for you guys, I would still be trying hose clamp and duct tape a lawn mower engine to a bike....
    laff
     
  20. professor

    professor New Member

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    Barely awake's answers are very good. A LOT of noise comes out of the intake tract- 2 or 4 stroke.
    All cars from the factory have an air box with a small snout coming out of it to kill the noise. I believe it is called a Helmholtz chamber (something like that).

    Look at a factory moped exhaust. Very long, and long silencing area too.
    Running dual mufflers helps. Years ago I ran 2 glaspacks (one in the center of the car and one in the rear)- straight thru, but I was surprised at how quiet it was- not at all like using one of them. Same principle- the more mufflering-the better.

    What Silver Bear said. When I would make comments on the Turbo forum to the new guys, I stressed having a quiet exhaust will let you hear the engine and any strange noise BEFORE it self destructs.
     

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