how to quiet an engine???

Discussion in 'Friction Drive' started by mrdc, Dec 17, 2012.

  1. mrdc

    mrdc New Member


    I was going to buy an ebike but they don't go far enough on a charge.
    I have found a nice friction drive set up but it's too noisy even though it's a 4 stroke.
    how can i make it REALLY quiet?

    it'll never be as quiet as an ebike, but i ride mostly after midnight so i want an uber quiet bike.

    any ideas?

    thank you

  2. jaguar

    jaguar Well-Known Member

    Install an extra muffler in series with the existing muffler.
    Timbone likes this.
  3. mrdc

    mrdc New Member

    has anyone done that?

    is it an easy mod?
    Timbone likes this.
  4. jaguar

    jaguar Well-Known Member

    Any dum-butt welder can weld another muffler on.
    Only other alternative you have is to design and construct your own super muffler.
    Timbone likes this.
  5. darwin

    darwin Well-Known Member

    What 4 stroker? Your lucky you didn't order a 2 stroker buzz saw. Stay away from a Chinese fd kit, they are notorious for poor quality and wasting your money.
  6. mrdc

    mrdc New Member

    i haven't bought one yet.
    i'm still researching.

    i have my eye on a honda 4 stroke on a schwinn mtb.

    But i listened to one run on youtube and there is no way. just too loud for late night rides.
  7. darwin

    darwin Well-Known Member

    Honda 35cc motor or a soobie is as quiet as you can get. I've owned both and currently the Honda 35 and it is quiet. You throttle down when necessary and its decibal level is nothing to the human ear. Cheaper than the soobie too when new.
  8. darwin

    darwin Well-Known Member

    Wide open its sounds like a lawn mower going, half throttle when in the hood its barely noticeable. AT night your careless to be going full throttle in the city unless trying to outrun the popo.
  9. mrdc

    mrdc New Member

    thanks for the great info!
  10. CurtH

    CurtH New Member

    I am curious if this causes lower performance.
  11. Timbone

    Timbone Active Member

    Big bump. The answer is no as you most likely have no expansion chamber.

    Take a small can - it must be strong. Fill it with shredded steel wool. Make sure you have at least 1/2" round for gasses to escape and a baffle to keep the steel wool from falling out. Just weld it onto the end of the stock muffler!
  12. Frankenstein

    Frankenstein Well-Known Member

    The topic is a 4 stroke, how in the world it would be too loud being a friction drive (read: small motor) is beyond me, maybe the video he watched had a modded muffler, in either case stacking in series shouldn't do squiggly poo to a 4s.

    On a 2 it might, just as you said, most likely if it has an expansion chamber, though who cares if you got it tuned in well enough you should be going fast enough that the sound you're making should pass in a split moment, not around long enough to piss people off.
  13. Steve Best

    Steve Best Well-Known Member

    This thread goes back to 2012, and the original poster never made any other posts than these.
    I assume this old post was resurrected out of curiosity about the original question.

    Exhaust is only one source of noise, once you quiet that, you start to hear the other sources.
    In rough order of importance and solutions:
    1) Exhaust from exit, fix leaks, longer more efficient muffler, new fiberglass packing in muffler, take off from center of the resonant chamber
    2) Exhaust from pipe chamber walls, thicker or double wall (ideally with absorbent packing) resonant chamber
    3) Intake noise, better filter and cover design (thicker, more absorbent materials)
    4) Gear noise, gear cover sound deadening (rubber or silicon padding), thicker tacky grease
    5) Cylinder noise, silicon dampers between fins, shrouding (cor-plast), tighter piston clearance
    6) Chain/sprocket noises, plastic chain guards

    Quiet makes the ride less tiresome, draws less public (and John Law!) ire, allows you to ride more places and lets you hear problems (detonation, mechanical) before they get worse.
  14. CurtH

    CurtH New Member

    I did post out of curiosity as Steve Best mentioned. Thanks for the replies, they were helpful. I am in the research phase of motorizing my bicycle and just gathering information.