Piston ring end gaps

[jdgherasim]

Hello everyone, this is my first time posting here so i hope i’m in the right section. i have a 1993 sea doo 587 motor, compression test read 118 and 120 on both cylinders. i took it apart to see how everything looks, cylinder walls look perfect, as well as the pistons. pistons have been replaced before; the part number on top comes back to a standard bore wsm piston. the cylinders are still factory bore (76mm), and the piston to wall clearance is within spec. my main concern is the piston ring end gap is massive on all 4 rings, almost 1.5x the wear limit. they’re measuring right around 1.5mm, i’ll link a photo. theres no way the rings could have worn down that far, is there?

could i get away with honing the cylinders (i have a ball home thats the perfect size) and new rings? not looking to throw a ton of money into it, but i’ll do what has to be done to bump up the compression. thanks!

 

[mikidymac]

Sounds like SBT quality control. If pistons, cylinders and piston to cylinder clearance is in spec the rings are junk and new junk rings might not make it better.

 

[jdgherasim]

Sounds like SBT quality control. If pistons, cylinders and piston to cylinder clearance is in spec the rings are junk and new junk rings might not make it better.

yup they’re sbt. i was thinking of ordering a different brand being that apparently sbt rings are oem size and can fit oem pistons and vice-versa, but i’ll have to see. worst case i order something and send it back if it doesnt work out.

 

[mikidymac]

No, SBT, WSM and PRO-X rings will not fit OEM pistons. OEM pistons use an "L" shaped top ring.

 

[jdgherasim]

interesting, my top rings are an L shape, but they’re sbt pistons. maybe someone threw used oem rings onto the new pistons for some reason?

 

[mikidymac]

No, just didn't think SBT used the "L" upper ring.

 

[jdgherasim]

No, just didn't think SBT used the "L" upper ring.

makes sense. i think i’m just going to order a full top end kit to play it safe considering my cylinders are fine, i had a buddy or mine measure them with a bore gauge, gave him the specs and he said taper was within spec and they were not out of round. hopefully that’ll bump up my compression and sort out the thing running weird.

 

[mikidymac]

I would suggest WSM top end over SBT.