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  1. #1

    WSM 4-tec piston clearance

    Hi
    Just got my WSM 010-861-05PK forged pistons for my 2003 SC 185 engine.
    In the box there was a little note that seems very universal for all their pistons saying that the clearance should be 0.0045 to 0.005.
    That seems very loose to me. Looking at the shop manual and the service limit is at 0.004??.
    So i plan to bore with clearance at 0.003, do you think that is wise or should I follow the note and bore 0.004?


  2. #2
    Bob 1tommygunner1927's Avatar
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    It depends on how much boost.....same for the ring gaps.

  3. #3
    Thanks, everything is standard SC 185HP.

  4. #4
    Bob 1tommygunner1927's Avatar
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    Best to check with WSM for your specific needs.

  5. #5
    ou812's Avatar
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    I didn't get a note with clearance specs on my .50 set for the 215 hp. I was able to dig up info on the 215 motor though. .002-.004
    I went .030. I'm not sure if the clearance is different than the 185's though.

  6. #6
    WSM says .0045-.0050 but I don't like those numbers, if it was a 2-stroke yes, but not in this case.
    I think i go for .003 as ou812 did, it feels reasonable because it is still way more clearance than specified for the OEM forged pistons.
    Thanks.

  7. #7
    ou812's Avatar
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    Quote Originally Posted by umh View Post
    WSM says .0045-.0050 but I don't like those numbers, if it was a 2-stroke yes, but not in this case.
    I think i go for .003 as ou812 did, it feels reasonable because it is still way more clearance than specified for the OEM forged pistons.
    Thanks.
    Just so you know, CP pistons run fine at .0035 sometimes 4

  8. #8
    3 to 3.5 on mine

  9. #9
    Differnt piston mfgers use diferent alloys to mfger there pistons & use different webbing in the pin boss area... All of this causes a different expansion rate when the engine comes to temp.. I used .003 on a set of WISCO forged. A High End Motorcycle Machine Shop can normally do the job nicely..... P.S........ 4 -4.5 would be about right for a piston that does Not have a Oli Ring. Like a 2 stroke..

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