yamaha piston to bore measurements

[Mouthfulloflake]

so ive got some cylinders, and pistons, some are matched sets some arent.

If I knew the range of piston to bore clearance, I could maybe make better use of some of these pistons.

I plan to hone and re-ring the ones that dont have terrible taper, but I need some starting point for measuremtns.

all pistons appear to be ART or SBT cast pistons, no forged pistons.
and YES the sbt pistons scare me a little, although they look very similar to the art pistons.

 

[sjetrider]

I have run from .003 to .007 clearance on ART and OEM pistons with no problems and long life. This is assuming that the pistons and sleaves are score free. Hope this helps. Keep in mind that OEM pistons run .002 to .003 larger that ART pistons (tipacally) so if your bore is .008 larger than the ART pistons then get some new OEM's and go. I am currently running .0065 on OEM pistons on a 10 year old bore with fresh hone and have been since beginnig of last season (215 compression):bigeyes: runs great. This cylender is ported and has been for 10 years and has amazed me as to how long it has held up on only the second set of pistons and rings with one hone.

 

[Mouthfulloflake]

thanks!

recognize your old 650 pistons and bore in that pic?

that top end will probably get ported and stuck on 61x cases for my sons boat.

 

[beachedflunkey]

The manual says .028-.003 for clearance. I'm fixing to fire up a rebuilt top end with just under .005 :fingersx:

 

[accbr]

The specs start on page 5-10. I can't remember who posted this, but it's better than the manual I already had.


http://www.drmikesandy.com/xh2o/Yamaha SuperJet Service Manual.pdf

 

[Mouthfulloflake]

awesome info, what in the hell sort of a crack pot doctor has pirated manuals on his website?