On a 2002 sportsman 500 I'm lost on the manual as far as piston ring instillation,the manual is for up to 99 models. It states the top rail has a locating tab to prevent rotation.The tab must be positioned in the notch on the side of the piston....Any help appreciated

 

The new polaris 3087224 ring set.. the top oil control rail has no locating tab to prevent rotation unlike the ring I took off, both oil control rings are the same

 

Replacement pistons whether stock or aftermarket don't have this this indention on some later model pistons. Didn't work anyway as the oil rings can move a little. Just stagger the compression rings ends to each side of the piston away from where the exhaust valves/port will be when the head is installed. Just stagger the oil ring ends away from where the intake valves/intake port will be. In other words you want the solid portion of all rings to be at the intake and exhaust area.This is the main wear area on rings,front and rear.Plus you can see on the parts break down all rings have updated part numbers which usually means they've been changed.http://www.cyclepartswarehouse.com/f...2002&fveh=5582

 

Thanks OPT, was confused seeing one of the old oil control rings had a lip and the new Polaris set didn't

 

OPT, the end gap on the new top ring is .020" which is a bit much IMO, .008" sounds better to me, the machinist said the bore was good so he just honed it, I'm thinking it needs a bore job? It was not smoking when it got into deep water and cut off but never restarted after due to a stuck compression ring and a lot of mud

 

Sounds like it needs at least a first over Polaris piston OR imo a Wiseco. Ring end gap is supposed to be between .008-.014. Measure the cylinder base clearance against the piston skirt dimensions. Pistons are set tight! 0.0006 - 0.0018 on Polaris cast pistons! 0.0024 is considered the service limit. Choice is yours as to a Polaris oversize replacement or a Wiseco,but Wiseco may have a little looser clearance specs because it's a forged piston,but shouldn't be much more than factory specs. Sometimes you can get by with just replacing rings on a 4 stroke,sometime you can't if worn past stock bore dimensions.Stock bore range is 3.6216 - 3.6224. If the new std rings have too much end gap then you know it needs to be bored.

 

Not sure what the machinist he used was thinking especially seeing we left him the specs but we need to find another. A Wiseco 92.5 should work... Would you recommend taking the cylinder to a new machinist and let him recheck the bore first or just order a 92.5 and take them both together to get bored? Like you said and I agree it might run but I'd prefer to know it's right vs on the verge...

 

Just out of curiosity were you really able to bore them that tight OPT? My machinist for my last two builds said he really couldn't get it tighter that about .0023
I run CNC's during the summer and that is a dang tight fit for parts!

Also as long as the comp rings are staggered that's all that matters. Have heard and experienced that the rings actually rotate throughout their life. On my tear down of my first Wiseco piston the oil pump claimed the ring gaps had actually aligned themselves to the same spot.

It sounds like the first stock oversize would fit well, it's only a 92.25 so there's still room for more rebuilds should it ever need them.

1999 Sportsman 509. wiseco 93mm forged piston. Moose gaskets. CRU aftermarket HO camshaft. new diaphragm and block. Summit water temp gauge. EPI clutch rebuild. custom spacers on both clutch springs. runnin Mobil 1 0W-40

 

The trick on the 500 is to bore it to piston skirt size or slightly below,use a medium hone,then a finer finish hone to size.Cleaning and checking along the way.You have to have a good set of honing bars which we had.Cast pistons I did set right at .0018-.002 or as close as I could possibly get.Then checked ring end gaps in the cylinder. Another key is to let the engine come to operating temperature when you first crank it up,kill it,let it cool down and repeat.Then take it out for a spin. Never had a problem or a comeback that way when I rebuilt top ends myself.Same as I did for the 2 strokes. Wiseco calls for(or used to)a little larger clearance ratio because of the forged piston and I would allow a tad more,but not much. Again engine break in is the key.Even some good machine shops can allow just too much clearance when they bore cylinders.

 

Do you let it idle OPT during the heat up cool down sessions at base idle speed?