wiseco piston question!! HELP!!

[poopski]

I just bought a set of 86mm wiseco pistons, and opened them to check em out and noticed each piston has a hole in the skirt on the intake side? It might be a stupid qustion but what are the holes for? My old pistons do not have any holes??

 

[SUPERJET-113]

All the Yam 760 pistons Ive seen(84mm+) have all had that hole. Ive seen it on OEM(ART),Pro-x, Vertex, and Wiseco 84mm+ pistons.
I dont know what the theory is behind it?
Extra lube hole for the wrist pin/bearings? :dunno:

 

[Rickster]

Are those flat top or domes pistons?

 

[poopski]

the are domed

 

[#ZERO]

The hole is for cooling the underside of the piston crown and it's on all 62T oem style pistons.

 

[2XLR8]

That is the old part number. Those are the older pistons. Different alloy composition they need a little more clearance than the newer ones.

 

[poopski]

yep, about .0065-.007???