Tip: How to reduce engine noise.

Discussion in '2-Stroke Engines' started by iRide Customs, Sep 22, 2007.

  1. iRide Customs

    iRide Customs Member

    A friend of mine was over last night and he mentioned something that I never really thought about.

    Has anyone ever seen the rubber bushings that were sometimes iserted inbetween the fins of two stroke motorcycle engines? Well I have seen them a million times but never really knew why they were there. Well, my friend Luke enlightened me...they are for sound deadening. I tried it on my Dax 70cc and it reduced that high pitched engine whine by about 50% and I only put it in about 5 different places.

    To get an idea of how it works, simply grab the 2 outside fins on the head of a Dax 70cc (before the engine warms up, obviously) and hear the difference.

    I am going to put bushing between every fin on my engine. Yes I am going to use bushings that won't melt.


  2. OldPete

    OldPete Guest

    Yes it does work. Bond them in with a dot of high temp silicone so they do not vibrate out.
  3. But what of cooling? I would think anything between them cooling fins would obstruct cooling.
    We need pics and where to go ect.
  4. iRide Customs

    iRide Customs Member

    It only takes small pieces of rubber to acheive the desired result. I don't think it impairs cooling at all. Richard and I just got back from a 15 mile ride and had no problems with overheating.

    I will post a couple of pics here in a little while.

  5. Yes Pics please! ;-)

  6. iRide Customs

    iRide Customs Member

    Ok...here is a pic or 3 of what I did. I tried to make the rubber small so it would not interfere with air flow too much.

    Attached Files:

  7. That's it? AWESOME!! I pictured these rubber inserts going all the way around the fins.
    This is a real dumb question,but my brain isn't working tonight. Where did you get those rubber pieces? The answer I bet is so obvious but right now I'm drawing a blank for some reason.
  8. iRide Customs

    iRide Customs Member

    Not so obvious...the rubber pieces were scavenged from where I work. It's gasket material for the man holes on 1,000,000 gal. tanks.
  9. motor puzzle

    motor puzzle Guest

    Temperature gauge

    How about a little experiment: Installing a temperature gauge (has anybody done this?) and do a before and after dampening. I think you would have to install the sensor in the back part of the engine as this would be the part affected by the possible lack of airflow. My guess, you would see a difference at normal operating speeds. I would volunteer but I'm still piecing my bike together, and it's going very sloooowly.....
  10. OldPete

    OldPete Guest

    When noise became an issue in the mid '80s many air cooled M/Cs used rubber damping blocks in the fins. There was never an over heating problem. It does not take alot of rubber to be effective.
  11. Good Pics! I noticed you skipped every other group of 2 fins .....would it help even more to put a rubber spacer between every fin?
  12. gone_fishin

    gone_fishin Guest

    yikes!! great contribution dan!!! another adendum to my "things that i haven't done yet" list :)
  13. JemmaUK

    JemmaUK Guest

    Would that work for the GEBE 25cc kit?

    The silencer - when its working and not commiting mechanical suicide is good for sound - sounds sorta a little deeper than a moped - specially when freewheeling/closed throttle...

    but from what I have seen of the motor I only have very small finning on it - so where is the rest of the noise coming from?
  14. OldPete

    OldPete Guest

    Your GEBE 25cc, be it 4 stroke or 2, will be forced or fan cooled. Modern engines of this type will have thin, short, tightly spaced fins that would not benifit from these rubber inserts as an open or unshrouded engine would with its long, widely spaced, thick fins. The shrouding helps contain some noise BTW.

    Mechanical noise will come out of both the intake and exhaust on both 2 and 4 stroke motors. In fact, exhaust sound comes out of a 2 stroke intake big time because both ports are uncovered for so long when the piston is at BDC. :cool:
  15. gone_fishin

    gone_fishin Guest

  16. Jim H

    Jim H Guest

    I remember seeing rubber spacers on the old Hodakas and Bultacos; never knew what they were for though...
  17. In search of rubber ( :D ) I decided to cut up a torn up bicycle tire.
    My evaluation:
    It most definetly runs quieter and when I wind it out,it dosen't vibrate as hard!

    Wow. This is like the simplest modification yet to a Happy Time that yields more Happy!

    iRide RULES!!!

    Attached Files:

  18. Just curious but would welding an aluminum strip vertically from the bottom of the cylinder jug to the top of the cylinder jug accomplish the same thing PLUS improve cooling since it is added surface area?....I will definitely try the rubber trick tho....just happen to have a spare inner tube sitting outside....

  19. OldPete

    OldPete Guest

    Welding would introduce warpage. Rubber will not effect bore dimention with expansion and contraction as the engine's heat cycle varies as a welded inplace bit of aluminum would. However...some engines have struts cast inplace with the cylinder at time of manufacture.
    The rubbers used on motorcycle engines are very hard. I have some here for a Moto Guzzi project.
  20. Dockspa1

    Dockspa1 Guest

    Question, Augie,
    Did the heater hose stay in place and if it did , did it melt?
    Did it make a big difference?