Blown Piston Ring... what exactly happened?

[IDoSeaDoo]

I recently was using my 97 SPX to tow in my GTS which decided to stop sparking and what do you know, one of the cyliders in the SPX had 0 compression afterwards. Pulled the head and wasn't surprised to find a little piece of the piston ring chillin on top of the piston. Why would this happen? Could it just not handle the load? My cylinder wall is a little rough, but not grooved, do you think I can get away with putting in another piston (I have spares)?

Thanks

 

[Dr Honda]

Had nothing to do with the load of pulling a ski. The ring could have been fractured from sitting over the winter, and building a little rust. Or, the piston crown could have been eroded from a lean run... or they stuck because of the wrong oil.

If the jug is OK... you could hone it, and put in a new piston and ring. Just make sure the tolerances are OK, and make sure that there isn't any bits of piston down in the crank.

 

[IDoSeaDoo]

Thanks Doc, I got my bore gauge coming in the mail in a few days. Will measure out-of-round and the bore. I have an assortment of spare jugs/pistons. I need to tear this engine and replace the wrist pin bearings anyway, I guess it's time...

BTW Doc, what do you think of SBT pistons?

 

[Dr Honda]

BTW Doc, what do you think of SBT pistons?

I don't have any problems with them. I've used their top end kit's a few times, and didn't have anyone come back and say... "you built me a crap engine"

I personally like the OEM pistons... but they are expensive.

 

[IDoSeaDoo]

What type of micrometer do you use to measure piston width? I have an old vernir caliper (The basic kind w/o the dial). I think it's accurate to the .01mm... but I can only measure either the crown, or the skirt. What do you use?