Correct WSM 4-tec Piston clearance?

[umh]

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?

 

[ski-d00]

Do NOT bore at .0030" clearance. The motor won't last long if you do. The wear limit is .0039" You should bore at .0015" clearance.

The 0.0045" to 0.0050" is for the 2 strokes, not the 4 strokes.

NOTE that these are in inches, not mm. This is how we do it in the US machine shops even with pistons measured in mm.

 

[umh]

Thansk for your answer.
So you are saying that .0030" is way to large. Even if WSM adds a note in the piston carbord box that I should bore .0045"-.0050"?
Is .0015" really a clearance for a forged piston used on an SC motor?
Thanks
/Peter

 

[ski-d00]

Yes, way too big. As I said, the .005 note is for 2 strokes only, not sure why wsm would put that in for a 4 stroke piston. A 4 stroke won't even run worth a crap at. 005. I've done tons of them. Yes, forged sc 100mm pistons.

 

[umh]

Sorry to asking again, it is very important to get this right.
The 0.015" clearance that you recommend, is it only for OEM pistons or do you think the same clearance goes for WSM (my pistons) and WISECO?
/Peter

 

[ski-d00]

every piston mfg will have different clearances which depend on the alloy/heat treating/forged process. I only use OEM seadoo which is what I recommend and the clearances I gave you, even used is better than WSM imo. Maybe WSM does recommend that huge clearance but it would be surprising and a red flag to me. I suggest checking with WSM to confirm. I have used WSM for lots of 2 strokes and they have worked well.