Oversized Piston diameter

[IDoSeaDoo]

Hey all,

I need a set of pistons for my 787, and I have a lot of cylinder jugs with various bores. I measured them all, and seem to have some that are identical, but not exactly 82mm. My question is, how to they manufacture the oversized pistons? When they say .25mm over, does that mean that it's for a .25mm oversized BORE? Does that mean the piston will be .1mm smaller than the bore (82.15mm)? When I ordered std. size pistons, they were 81.91mm, which is right in stride with the specs for cylinder-piston clearance.

 

[IDoSeaDoo]

I think I just answered my own question. Went on one of those "Buy oem seadoo parts" websites, and the scroll menu had pistons in their actual diameters. The std is actually 81.89mm, and the next oversize is 82.14mm. The retailer is PROBABLY not going to know this, even the WSM techs (I had to dial a special number) were pretty lame in beating around the bush because they didn't actually know what the diameter was. I kept trying to explain to him why I needed this number, and he seemed to just get irritated and claimed he "had another call". Convenient after his 2min wrap up...

 

[Dr Honda]

You buy the pistons in the next size bigger. Then you measure them... and cut the jug to the new piston + it's expansion tolerance. (around 0.004" to 0.015" depending on the piston)