Piston Wash / Wear

Discussion in '2 smokers' started by kclark, Oct 15, 2012.

  1. kclark

    kclark 1SevenZero

    Joined:
    Oct 14, 2010
    Oddometer:
    90
    Location:
    Washington
    So yanked my top end apart to replace the piston rings. And this is what I found.

    [​IMG]

    This was the wear on the intake side of the piston. It's hard to tell from the pic, but the two pronounced lines are deep galling. there was some light galling on both sides of the deep galling. The exhaust side had no galling and what appeared to be normal wear. It's a Wiseco forged piston. What would lead to this kind of uneven wear on the skirt?

    [​IMG]

    So... if I've read all the piston wash forums right, then I would read this to be rich. Is that correct?

    A little additional info on the bike. It's a 99' Suzuki RM 250. I bought it used and this is approx. the 10th hour on the new Wiseco piston. I measured the cylinder and it is well within spec for wear. I can still see hatch marks. He told me he blew up the top end and thus the reason for the rebuild when he did it. There is some minor galling in the bottom of the cylinder wall. It appears very minor, not visible, but can feel it with my fingers, and no sharp edges. Additionally the galling does not appear to be on the same side as the sever galling on the piston skirt.
    #1
  2. kclark

    kclark 1SevenZero

    Joined:
    Oct 14, 2010
    Oddometer:
    90
    Location:
    Washington
    Forgot to mention there has been absolutely no odd sounds from the motor when running. To me it felt flat at half throttle, but others said they never noticed it.
    #2
  3. JonnyCash

    JonnyCash turd polisher

    Joined:
    Jan 22, 2011
    Oddometer:
    1,821
    Location:
    Midcoast, Maine
    Sometimes if the port windows aren't well chamfered and smoothed nicely, they'll scuff the pistons. The tops and bottoms of the ports will snag rings and skirts, but the sides will gall and scuff like that.Every time I pull my RD apart, it looks kinda like that, no matter how well things are smoothed out though. Not as bad as what you're showing here though.
    #3
  4. Twin-shocker

    Twin-shocker Long timer

    Joined:
    Jan 28, 2012
    Oddometer:
    1,673
    Thats caused by sand/dirt being sucked into the motor through the intake.
    #4