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  1. #1

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    WSM piston problems

    So over a year ago i started rebuilding my SL900 and just a few weeks ago i finally sent the jugs out to get bored. I bought the WSM pistons about a year ago. So here is the problem the pistons are tapered. The jugs are done but i cant get the piston in. The skirt end of the piston is thicker than the top. if we put the piston in the jug ring side down it will slide in the jug about half way. Is this the kind of crap this company sells. These are the first set of pistons i bought that were not wiseco. All 3 pistons are the same way. So now how can you have clearance specs when the piston is not straight. I got a email in to the company. The problem is i bought them a year ago and they sat on my work bench until a few weeks ago. They are brand new. Anyone else ever see this? I havent. Lets just say i have put together a few engines over the years and never had issues with wiseco. I am kicking myself in the arse for not getting them in the first place


  2. #2
    CHICKA WAH WAH bren's Avatar
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    havent seen any quality come from those pistons mate, sorry youve had em so long.

    I think they come out of the same place they got the olympics at the moment.

    Weisco, Pro-X, VP all good but I'm afraid WSM doesnt make that list

  3. #3
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    I have used WSM and never had a problem,as alot of guys here have. Have you measured them? How much differance is there?

  4. #4
    i also just bought 1 set wsm piston....havent tried it yet...but they say its good

  5. #5
    ph2ocraft's Avatar
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    I've seen a few guys go with the WSM as of late but I prefer the factory Elko's or Wiseco.

  6. #6

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    Aren't they suppose to be tapered from top to bottom because the rings make the top tight . sounds like the guy didn't bore the cylinders right ???

  7. #7
    PolarisNut's Avatar
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    Quote Originally Posted by Spun Monkey View Post
    So over a year ago i started rebuilding my SL900 and just a few weeks ago i finally sent the jugs out to get bored. I bought the WSM pistons about a year ago. So here is the problem the pistons are tapered. The jugs are done but i cant get the piston in. The skirt end of the piston is thicker than the top. if we put the piston in the jug ring side down it will slide in the jug about half way. Is this the kind of crap this company sells. These are the first set of pistons i bought that were not wiseco. All 3 pistons are the same way. So now how can you have clearance specs when the piston is not straight. I got a email in to the company. The problem is i bought them a year ago and they sat on my work bench until a few weeks ago. They are brand new. Anyone else ever see this? I havent. Lets just say i have put together a few engines over the years and never had issues with wiseco. I am kicking myself in the arse for not getting them in the first place
    The pistons are supposed to be tapered like that. All 2 stroke pistons are like that. It keeps the dome area (hottest area of the piston, therefore it expands more) from seizing. When the pistons are at operating temp, the clearances even out. FWIW, Wisecos are tapered more than any other pistons, because they are forged, and not cast.

    Sounds like you have oversized pistons and standard sized bore...or the bore isn't oversized the correct amount.

  8. #8
    Did u send the pistons with the cylinder when u had them bored?

  9. #9

    Join Date
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    Quote Originally Posted by PolarisNut View Post
    The pistons are supposed to be tapered like that. All 2 stroke pistons are like that. It keeps the dome area (hottest area of the piston, therefore it expands more) from seizing. When the pistons are at operating temp, the clearances even out. FWIW, Wisecos are tapered more than any other pistons, because they are forged, and not cast.

    Sounds like you have oversized pistons and standard sized bore...or the bore isn't oversized the correct amount.
    +1 Pistons are always tapered. Your machine shop needs to bore the cylinders to match the pistons. Most shops wont touch it without the new pistons. I'm guessing but I'd say your bore is about .006" undersize if the pistons will go half way in. The machine shop should be able to hone to size.

    At least it was off a sizable amount. Could have just slid in - then you would have stuck a piston first time out. Piston to wall clearance should be .0045" if I remember right on WSM.

  10. #10
    ph2ocraft's Avatar
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    So spun monkey have you ever verified the problem was with your machinist?
    If he had the piston, it seems like a pretty large error on his part.

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