1. Adventure Rider Print Magazine!
    We're doing a print magazine this November - 128 pages of high quality adventure riding stories, photography and interviews!

    Click here to purchase a copy for $9. Limited copies still available.
    Dismiss Notice

1982 YZ490 trail machine

Discussion in '2 smokers' started by mudmantra, Sep 28, 2013.

  1. slideways

    slideways EspaƱa

    Joined:
    Mar 1, 2003
    Oddometer:
    14,269
    Location:
    Spain
    Plus one.

    I had that same bike back in the 80's.

    I think that long silencer may be causing you some tuning issues.

    Also make sure the packing is not saturated with oil.

    I ran a DG pipe on mine and put some air box filters in it to let it breath better those 490's need a lot of air. Once you get the jetting figured out it will run great.
  2. mudmantra

    mudmantra Been here awhile

    Joined:
    Jul 6, 2009
    Oddometer:
    364
    Location:
    Humboldt
    Yes I'll try some bigger main jets. The silencer could now be soaked with oil. I'll check and maybe repack it. It's pretty easy to do, just a snap ring holds it all together. The pipe is a DG, I could get a DG silencer for it. It would be better if I could find a silencer with a spark arrestor. I though about opening the air box. With the porting done, it really wants to rev out more. Maybe it needs more air too.
  3. mudmantra

    mudmantra Been here awhile

    Joined:
    Jul 6, 2009
    Oddometer:
    364
    Location:
    Humboldt
    I removed the 420 main jet and replaced it with a 440 main jet. It runs a lot better. I tried holding it at different throttle settings and it ran steady and clean at all, except 40 percent was not as smooth as the rest. I might be able to tune that out with the air screw.
  4. KX50002

    KX50002 NooB, my ass

    Joined:
    Mar 18, 2012
    Oddometer:
    2,079
    Location:
    NEPA
    40 percent should be needle territory