What sized piston rings should i go with on my XP 787?

[RockyRiver]

Can't say how much I love this site. So glad I found it. Laid in bed last night until 3:00 A.M. reading posts. (Much to the grimace of my Wife lol). Quick question regarding ring selection. My 97 XP has been sluggish to start so I did a compression check and found around 100 on each cylinder. So being bored I decided to pull the head and take a look. Inside was very clean and on top of the piston is states the size as 81.89 stamped on top of the piston. The pistons are both very clean with no chips, scorring or excessive carbon build up. Cylinders are perfect as well. So rather than miss a bunch of riding time I am thinking about just cleaning up the cylinders and installing new rings.
This Winter when I have down time I will probably pull the engine and go into a full rebuild but don't want to do that at this time.
I am the second owner of the ski and the original owner was a friend of the family who bought it new and kept it on top of his massive houseboat for years and never rode it much. The ski probably has around 150 hours max.
I don't plan on changing the pistons out until I do the whole thing this winter so what rings should I go with for this application with the I assume stock pistons?
Raced bikes for years and have tore down and redid the top end on my CR's to many times to count but I'm a little intimidated by these for some reason? Thanks for such a awesome site. Definitely signing up later this month for the Premium!!!!

 

[glsmohio]

If you can get away with the same size i would just hone it and reinstall. You could always just rering it also

 

[soccerdad]

A 150 hour ski should have better compression than that. Are you SURE your gauge is reading correctly? Not sure why it would be that low if the cylinders look cherry. Sluggish starts could be a variety of things besides rings. You may be correct, but just wanted to throw out a sanity check before you tore it down.

Oh.. And wecome to the coolest forum around.... at least for two stroke Seadoos...

 

[skewba98z28]

Considering standard bore is 82mm i'm assuming 81.89mm means you have standard bore pistons. You need standard bore rings which are listed as 82mm. WSM Rings should work just fine for you. Its not hard to do. Just make sure you get the base gasket and manifold gaskets sealed. I always use copper coat in a spray can and have had great with it. Make sure your ring end gap is correct also.

 

[RockyRiver]

Considering standard bore is 82mm i'm assuming 81.89mm means you have standard bore pistons. You need standard bore rings which are listed as 82mm. WSM Rings should work just fine for you. Its not hard to do. Just make sure you get the base gasket and manifold gaskets sealed. I always use copper coat in a spray can and have had great with it. Make sure your ring end gap is correct also.

Thanks for all the tips! I bought my compression gauge at Harbor Freight many years ago and it is probably a little off but I figure I would go ahead and change them out. I used to do my bikes after every 2 races whether they needed it or not so I'm learning the difference in these type machines. I really love this site though!!!!!! Ill probably just add the new rings and see how the old girl does until Fall.

 

[mikidymac]

Considering standard bore is 82mm i'm assuming 81.89mm means you have standard bore pistons. You need standard bore rings which are listed as 82mm. WSM Rings should work just fine for you. Its not hard to do. Just make sure you get the base gasket and manifold gaskets sealed. I always use copper coat in a spray can and have had great with it. Make sure your ring end gap is correct also.

Assuming it is stock WSM rings will not work on OEM pistons. They are a completely different ring design.

You have to order std. OEM rings number 420815100. Also make sure you use some kind of hone on the cylinders so that the new rings will seat properly.

I would also order the OEM gaskets because you will need to replace the base gasket with the same thickenss as is already on the engine and you will not know untill you pull the cylinders. There are holes punched in it to tell you the thickness and seadoo made like 6 different ones.

 

[racerxxx]

RIK rings are the same as stock IIRC

You can look thru the cylinders and see the holes in the gasket for the base gasket

 

[1983]

Try another comp gauge, and make sure throttle is open 100% and fuel is turned off when doing the test.

Oh and spark plug boots grounded.


Rob

 

[mikidymac]

RIK rings are the same as stock IIRC

You can look thru the cylinders and see the holes in the gasket for the base gasket

RIK makes most of the Japanese OEM rings but I am not sure about the seadoo OEM's. I do know that the WSM, SBT and Pro-X pistons I have seen have standard rings on the 1st and 2nd ring but on OEM pistons they use the funny "L" shaped 1st ring so I am pretty you need to use the OEM rings on OEM pistons.

 

[mikidymac]

Try another comp gauge, and make sure throttle is open 100% and fuel is turned off when doing the test.

Oh and spark plug boots grounded.


Rob

As 1983 said but also make sure you have a strong battery had hold the throttle wide open. If you do only have 100 psi it typically will not start in the water.

 

[racerxxx]

RIK makes most of the Japanese OEM rings but I am not sure about the seadoo OEM's. I do know that the WSM, SBT and Pro-X pistons I have seen have standard rings on the 1st and 2nd ring but on OEM pistons they use the funny "L" shaped 1st ring so I am pretty you need to use the OEM rings on OEM pistons.

http://www.ebay.com/itm/WSM-Sea-Doo...ash=item2ec3e51655:g:M-AAAOSwMmBV1bHx&vxp=mtr

 

[mikidymac]

Well, there you go... LOL, learn something new everyday.

Looking into it more it appears that both WSM and SBT use the "L" top ring just like OEM but Pro-X uses a conventional top ring.

Forget everything I said before.:thumbsup:

 

[racerxxx]

Well, there you go... LOL, learn something new everyday.

Looking into it more it appears that both WSM and SBT use the "L" top ring just like OEM but Pro-X uses a conventional top ring.

Forget everything I said before.:thumbsup:

We both keep each other in check. My brain has been mush lately.

 

[1983]

Yup WSM uses the " L " type top ring.

Im doing a STD. bore top end install tonight and tomorrow. Got a new hone in just now too. I am using the WSM basic kit.