Tips on quieting the muffler?

Discussion in 'Motorized Bicycle General Discussion' started by mxchris727, Aug 10, 2009.

  1. mxchris727

    mxchris727 New Member

    Joined:
    Aug 10, 2009
    Messages:
    34
    Likes Received:
    0
    I couldn't find any thread like this so I am starting a new one.

    I have recently finished building the 80cc kit and it has been running smoothly. The only problem I have is that the engine is too loud!!! I have tried putting steel wool into the muffler and have also tried putting pipe insulator around it. They both work well for about 5 minutes until they get to hot and burn to a crisp.

    Has anyone hushed their muffler successfully yet?
     
  2. Humsuckler

    Humsuckler New Member

    Joined:
    Jul 28, 2009
    Messages:
    458
    Likes Received:
    0
    instead of using steel wool, use R20 house insulation! dont pack it too to tight. (insulation doesnt burn up that fast, remember, its a building code thing)
     
  3. Nashville Kat

    Nashville Kat Active Member

    Joined:
    Apr 20, 2009
    Messages:
    1,433
    Likes Received:
    1
    They were bugging me to post photos on my thread about putting two 16 ounce beer cans around the pipe and extending it.

    here's a pic, before I rode tonight and the bottom one came loose because it's only taped and I have to get another radiator clamp for it-

    The duct tape was smoking quite a bit so I'm not sure how well that will work out- It probably adds a little quiet, but I'm sure not as much as the cans themselves-

    the only question- does it hold too much heat on the pipe?- a great heat shield otherwise and I suppose holes could be drilled in the cans- but then less muffled-

    If the duct tape burns off, then you'll have to just have to beer can lables showing- chose your poison!

    By the way, I painted both the motor and pipe with auto store touch up paint when I got my kit- (and a clearcoat)

    The pipe burned and peeled quickly, but the motor's always been fine- and looks nice in pale metallic blue- I guess it's like the black kits.

    how about some annodized paint? That might look good...
     

    Attached Files:

  4. BarelyAWake

    BarelyAWake New Member

    Joined:
    Jul 21, 2009
    Messages:
    7,209
    Likes Received:
    4
    You have a great idea there, one I just might do myself - but your simply using the wrong product lol

    Exhaust/manifold wraps are somewhat common on performance racing vehicles under the idea that keeping the exhaust gas temp as high as possible increases velocity and thus performance. A secondary benefit would be to keep the radiated heat levels down - in this case, away from your shins ;) For us, it should work quit well to quiet the noise a bit, I remember it took some of the "bang" out of the noise from my headers on my old truck.

    For $10 it cant be beat, remember to look for motorcycle wrap as automotive may be too wide.

    [​IMG][​IMG]

    It's available in a variety of colors, some variants are self-adhesive (but I would use fasteners anyway)

    Also remember the old equation; trapped water+metal=rust, but with the low replacement costs for these exhaust systems - I don't think that's a problem.


    Hey - thanks for the idea man, I hadn't thought of this, but I'll prolly skip the can extensions ;)
     
    #4 BarelyAWake, Aug 12, 2009
    Last edited: Aug 12, 2009
  5. mxchris727

    mxchris727 New Member

    Joined:
    Aug 10, 2009
    Messages:
    34
    Likes Received:
    0
    I looked up the motorcycle wrap and it seems good... but there is not much clearance between the pedal crank and the muffler. If I use the wrap, I cant petal. Is there anything I could put into the muffler that wouldn't burn and is not toxic?
     
  6. TerrontheSnake

    TerrontheSnake New Member

    Joined:
    Jun 1, 2009
    Messages:
    720
    Likes Received:
    0
    Stainless steel pot scrubbers... Works effin great and they don't burn at all, but they add resistance and therefore you lose performance. I think your best betwould be to focus on doing an expansion chamber and adding a silencer to the end of that. If you have a welder some plate metal and a hammer they are not that hard to do.
     
  7. restapukin

    restapukin New Member

    Joined:
    Jul 22, 2009
    Messages:
    112
    Likes Received:
    0
    or maybe it would be profitable to focus on the noise that comes from the inlet side of things - through the carby 'throat'

    on my grubee 49cc inlet noise is greater than exhaust noise,
    .......say 60% inlet noise vs 40% exhaust noise at a guess....

    I'm still thinking about easy ways to reduce inlet noise .... but i want to both quiet down the intake and improve performance (slightly) at the same time.

    This should be pretty easy, I'm thinking, ... given the lack of attention to inlet noise implied by the use of a small lightweight plastic filter box.

    restapukin
    X
    his mark
     
  8. mxchris727

    mxchris727 New Member

    Joined:
    Aug 10, 2009
    Messages:
    34
    Likes Received:
    0
    I am more worried about the exhaust because when the engine is revved, you can hear it from blocks away.... It sounds like a chainsaw.
     
  9. restapukin

    restapukin New Member

    Joined:
    Jul 22, 2009
    Messages:
    112
    Likes Received:
    0
    mmm.... yeah... noise bugs me, too, but all i'm saying is that we tend to think of the engine noise as being mostly exhaust noise

    but maybe this is not the case... listen carefully & objectively... listen "outside the square" if yer like...

    are you sure that your biggest problem is the exhaust?

    no big deal... i'm curious what others think, actually... is all...

    restapukin
    X
    his mark
     
    #9 restapukin, Aug 12, 2009
    Last edited: Aug 12, 2009
  10. restapukin

    restapukin New Member

    Joined:
    Jul 22, 2009
    Messages:
    112
    Likes Received:
    0
    just... the other day i got my head close to the engine & moved it (my head) around whilst listening to the noise output & blipping the throttle

    must have been a horrible sight....

    but i was thinking how loud the intake was & how quiet the exhaust was ...
     
  11. mxchris727

    mxchris727 New Member

    Joined:
    Aug 10, 2009
    Messages:
    34
    Likes Received:
    0
    I can actually hear how loud the intake is by holding down the kill switch while the bike is moving and playing with the throttle. It is not that bad until you let go of the kill switch.
     
  12. restapukin

    restapukin New Member

    Joined:
    Jul 22, 2009
    Messages:
    112
    Likes Received:
    0
    decibels are funny things, damn, a'm steering clear of them damnned decibel numbers...

    my hope would be that total engine noise minus inlet noise equals noise that at least sounds a bit more like a 4-stroke and less like a brushcutter....

    I could be wrong, but i plan to test the theory for myself...

    restapukin
    X
    his mark
     
  13. restapukin

    restapukin New Member

    Joined:
    Jul 22, 2009
    Messages:
    112
    Likes Received:
    0
    but back to your q about exhaust noise, which i do not want to hijack

    I did try extending the final outlet of the exhaust silencer with a piece of copper pipe with the same or slightly larger inside diameter as the i.d. of the outlet.... and about six or seven inches long...

    I was pleased with a small noise reduction but surprised at the large performance penalty this little bit of pipe produced....

    so i reckon you'd have to go for an immediate increase in the diameter of pipe used to connect additional exhaust boxes to the bizzo....
     
  14. restapukin

    restapukin New Member

    Joined:
    Jul 22, 2009
    Messages:
    112
    Likes Received:
    0
    reckon I'm gonna go for that exhaust heat-bandage idea.. nice one, BarelyAWake... that's something i've learned tonight....
     
  15. Nashville Kat

    Nashville Kat Active Member

    Joined:
    Apr 20, 2009
    Messages:
    1,433
    Likes Received:
    1
    I've wanted to try a longer pipe and muffler- I bought a sharp looking chrome extended pipe and muffler from Boygofast on ebay, for not much more than regular muffler, but it won't fit on this cruiser without some real modification that I have no time or energy for at the moment-

    This one is meant to pass on top of the bottom bracket right next to crank arms, and so it must be just the right angle. Mine isn't.

    If I cut this old pipe a few inches down and couple a segment to the new one, I can probably run under the bottom bracket, but I'd have to lose the kickstand and get a rear one- too much $$, but maybe I'd just not have a kickstand for more quiet.

    Also hanging long pipes and muffler gets complicated, but the solution might be to use THREE screw clamps- one on pipe and/or muffler, one running other direction as hanger and one around chainstay- (the clamps come in all sizes- about 2 7/8" inches or wider are needed to use around the 16 oz beer cans.)

    I was looking for some flexline of some type I've seen on photos of other builds, and haven't found anything yet, but maybe some unflexible copper extension tubes. Inside must be 7/8 inch to couple over exterior of other pipes. So if anyone has a line on this flexline stuff, let us know-

    There is a more expensive extension tube and muffler, chrome again, at livefastmotors sometimes (also on ebay), and it drops down under the bottom bracket and under the chainstay.

    Also an expensive expansion tube and muffler at Sick Bike parts I think-

    I've also though about cutting out a small plastic wastebasket that hugs the motor and mounting it, or using something like BMX number plates on the side- to muffle the sound of the motor otherwise- like the scooters are generally under fairings. But I'm not sure if that would keep in too much heat- my motor seems to run better cooler

    The 2 cycle will always be a bit loud, more than a 4 cycle sccooter or bike motor- but compared to many motorcycles, it isn't as bad, because they are not only loud and whiny, they also have a lot of bass throaty noise that at least our whiners don't.

    The beer cans really take a notch out of the sound and for only the cost of some screw clamps- My end cap had come off the muffler and now I have about 3-4 inches of aluminum beer can extension I've drilled some holes in the end to serve as endcap.

    (The duct tape has DEFINITELY melted down- NOT RECCOMMENDED!)

    I like to kill my motor a lot, if i'm coming up around people, on downhills, at intersections- just to be less conspicuous and less of a disturbance,

    to cool the motor down occasionally,

    and to save gas-
     
    #15 Nashville Kat, Aug 12, 2009
    Last edited: Aug 12, 2009
  16. Brvnkaerv

    Brvnkaerv New Member

    Joined:
    Aug 11, 2009
    Messages:
    31
    Likes Received:
    0
    I have seen a video where the fellow wrapped his muffler with Kevlar. I assume he sealed it with some sort of resin. I was thinking of using some standard boat fiber-glass tape and epoxy resin. Have any of you fellows tried that?
     
    #16 Brvnkaerv, Aug 12, 2009
    Last edited: Aug 12, 2009
  17. Humsuckler

    Humsuckler New Member

    Joined:
    Jul 28, 2009
    Messages:
    458
    Likes Received:
    0
    id think the fiberglass would dry out and get dusty. fiberglass does burn eh'....

    at least campfire logic told me so once...
     
  18. BarelyAWake

    BarelyAWake New Member

    Joined:
    Jul 21, 2009
    Messages:
    7,209
    Likes Received:
    4
    Yeah - w/o a doubt the intake is insanely loud, if ya think about it it makes sense - not only is air RIPPING through the thing, on a two-stroke if you peer through the manifold you can see the piston. Obviously this means there's gonna be some noise.

    Ultralight airplanes are mostly two-strokes, mine had a Rotax 440 and the intake was FAR louder than the exhaust, even louder than the prop roar. I bought an intake silencer and all of a sudden I has a stealth plane!

    It's a shame there's no readily available intake silencer for these kits, but the concept is simple enough. Here's a diagram of the one I had, even if it wasn't way too big, I wouldn't recommend buying ultralight parts - they're crazy overpriced.

    [​IMG]

    However from that pic you can see the potential for making one yourself, I'd be on this project except I have NO clearance at all near my carb... ah well, mebbe someone else will get an idea ;)



    edit: Haha, oops... sorry to jack the thread, I didn't see there was a second page already *blush*

    nothing to see here - move along :D
     
    #18 BarelyAWake, Aug 13, 2009
    Last edited: Aug 13, 2009
  19. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

    Joined:
    Jan 8, 2008
    Messages:
    11,529
    Likes Received:
    3
    You can make a larger intake silencer from some Tupperware, or similar softer plastic container.

    I have semi- successfully use Chore Boy in the muffler....don't get carried away or your performance will suffer. Steel wool burns well, fiberglass fills with oil and becomes a mess quickly.
     
  20. restapukin

    restapukin New Member

    Joined:
    Jul 22, 2009
    Messages:
    112
    Likes Received:
    0
    That's it, BarelyAWake .... but not only can the piston be seen through the intake... there is a part of the cycle when both inlet and exhaust ports are opened ... just after the exploded gases are let loose, when both ports are open

    Gas flow and sound energy wavefront are two quite different matters...

    think of the tidal wave surfing upriver against the flow & much faster than the river flow...


    So this is why hitting the kill switch does not reveal the true noise level that comes from the intake when the engine is firing

    restapukin
    X
    his mark
     

Share This Page