Screaming Primary Gears, noise fix

Discussion in '2-Stroke Engines' started by Egor, Jun 21, 2008.

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  1. Egor

    Egor Guest

    OK Troops you are going to like this. I found a new trick for the scream that comes out of the primary gears. I was riding along and got tired of listening to the gear noise, and put my hand on the cover, wow all gone. I decided to try a new trick, I took a tube of Silicone rubber and coated the inside of the cover with the stuff. I kept it clear of the gears, putting more at the outer edge and thinning near the center where the disk lifts out when the clutch is pulled in. It was a miracle, it is so nice. I have no idea why the Chinese made that cover so flat, I know there is not much room but dead flat! Oh well you will like this one. Have fun, Dave

  2. BSA

    BSA Guest

    That is definately going in my next build, cheers dave.

  3. [​IMG]



    I got something that may be A little better and way cheaper that I have been doing for years.

    When ever some one stops by to pick up a kit I tell them to save a small piece of card board from the box .Then take off the clutch cover .Trace the outside of the clutch cover with a pen on the card board and cut it out. Simply place the cutout piece and put it in the clutch cover and your all set.
    It really cuts down on the DB noise level and no harm or damage can come from this simple and free mod.
    Actually have the outline trace of the cover on the box from the factory's in the works( have my finger crossed).

    Trust me it works.

    Hope this helps

    Blue-Collar Bob
    Last edited: Jun 21, 2008
  4. crabdance

    crabdance Member

    Thanks for the tips...

  5. Ghost0

    Ghost0 Guest

    I think this works as well and may be a bit easier. It is a piece of rubberized plastic. It was glued on with contact cement. Seems to work very well. I have also heard of others using an old rubber mouse pad but I think that will not hold up to the abuse.

    Attached Files:

  6. Pablo

    Pablo Motored Bikes Sponsor

    I love the cardboard - so ghetto it's gotta be cool!! Nice idea looks like it touches just a tad, but will soak up excess grease!

    Attached Files:

  7. I could paint it or put a sticker on it Then charge $10.
    Then it wouldn't look so Ghetto..Lol.:grin:

    No grease soaked up..... this particular piece has been used for 3 years now.
    Actually I took it out of an older bike for inspection ,It was close by on the bench so I just placed it in A newer one as there was nothing wrong with it.

  8. Old mouse pad. Works great too...

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  9. fastboy9

    fastboy9 Member

    Nice! I'm going to do both then I think, thick rubber glued on to clutch cover with a cardboard pad on the the inside. From a distance the mechanical whine is the loudest thing on these engines.
  10. BoltsMissing

    BoltsMissing Active Member

    dumb question, but gotta ask.

    What would prevent the noise in the first place ?

  11. Probably a thicker cover, or a better metal...I think the noise is resonance(sp?) coming from the cover....
  12. BoltsMissing

    BoltsMissing Active Member

    I was thinking along the lines of the actual gear material itself. There does not seem to be any of that shiny case hardened on the teeth of the gears.
    Ofcourse, this would add to the cost, but..,less noise at source level.
  13. The primary is so noisey because of the cut of the gears, if they where helical cut they would be quieter, I just put a layer of silicon inside mine, some oil in there would also quieten it down, pity its not a wet clutch.
    The barrel fins make a racket to, you can chock them, see Ghosts pic. I used fuel hose. (see pic) both of these mods make for a way quieter engine.

    Attached Files:

    Last edited: Jun 21, 2008
  14. Snax

    Snax Member

    Der, what phil just said. :p
  15. fastboy9

    fastboy9 Member

    These gears are what are called straight-cut gears. On a car the gears usually mesh at a slight angle, making it quiter. On high performance transmissions and race cars, the gearboxes are straight cut. Much more noisy but there is less friction therefore less power loss.
  16. BoltsMissing

    BoltsMissing Active Member

    So the HT is considered as an ambitious piece of machinery.
  17. Lol dunno about ambitious, probably they made them straight cut for ease of manufacture, or they just copied somthing else, a lot of motor cycles have straight cut primary gears, though some also have helical, some even have a chain.
    Straight cut gears have more direct application of force, so yeah less drag and also have a higher failure point.
    When you watch the touring cars you hear that high pitched whine, thats the gear box, all straight cut, jump in your manual transmission car and reverse, you hear the whine, they make reverse straight cut and some of the older cars with partial syncro box's had straight cut 1st.
  18. BSA

    BSA Guest

    Straight cut sounds cheaper as well, that's the only reason why the Chinese engines have it.

  19. BoltsMissing

    BoltsMissing Active Member

    Yeah I know all that stuff Phil,( admitedly I forgot, been years since working)
    but when I look at a HT overall and compare apples with apples, it's obvious the steel and alloy mix is low quality, and fair enough ya get what ya pay for, ain't complaining.

    But IF those gears have straight cut, high quality finish, hardened etc etc, then it ought to reduce that whine significantly.

    Heck, I'd go for the helical gears and work on the engine's other standard issue nigglers to compensate power loss from helicals.
    At least there will be no noise at the source, rather than band-aid methods we gotta put up with.
    Or the HT gurus can offer a choice, straight cut for the speed freaks, or helical for the cruisers.
    Personally I'd go for cruise.
  20. blime81

    blime81 New Member

    Thanks for the cardboard tip bluecollar..... Did it last night and couldn't believe how much of a difference just a piece of cardboard could make!