Polaris 250 rings .10 over

[dew2]

I had some leaky seals and a bad running Polaris 250 2x4 mod W937527.Compression was 90 lbs.Just had the cylinder to a shop for measuring.Standard 72mm is 2.835 inches this cylinder is round and measures 2.839 and a bit wider at the bottom.The ring gap with the used rings is .25.

Here is my question>The piston has the ring stops that pin,Can I use the standard piston with a ring set .10 over?

The manual says ring gap seated in the cylinder should be .0009 to .0018.

I am disabled and it will only run me 800 ft to a mailbox once a day and maybe a little use around the yard,so a bore,and new parts are out fixed income cant afford that.

Can I go .010 over on the rings with the standard piston?

Thanks for any advice

[LT80]

No. Cant do that.

90 comp isnt too bad. measure the piston to cylinder difference. Max is .007.

Maybe just stock rings will do it.

You are already buying rings and gaskets. I see the piston is $104. Might have to get a new piston .025 over and have the cylinder bored.

powersportswarehouse.com for parts

[dew2]

I have the specs for the motor.I never start any engine without them the piston skirt clearence with the original piston is .0011 to .0021 according to the book.I have .0042.No place will bore .25MM over.They all start at .50MM or .020.I cant afford that.Creating to much compression has at times on old used engines created lower case problems. I have one engine here bored,crosshatched, ringed and piston with new pin bearing.ran as breakin 1 hour later the rod broke. rod had 3300 miles of stress on it. Can you please explain why a .25MM over ring wont work??

Thanks for the reply out of 3 posts on 3 different sites your the only one who tried to help!! Thanks

PS I am a outboard mechanic,I have plenty experience with 2 strokes.These pistons with that ring stop pin has me baffled.I have and can yet put a file to the ring if the pin area needs to be made to the same size as a standard ring.I just want to be closer to specs when I put it back together.

Edited September 17, 2014 by dew2

[LT80]

Ok, Im reading that as you have 4 thousandths clearance. That is within spec. Id get stock rings.

To explain about the .25mm over ring thing:: you would need alot more clearance to get them to fit.

The pin in the piston is so the ring ends dont ride over the ports and cause damage. 4 strokes dont have the pins cuz the rings are supposed to spin.

The ppl you asked about boring is goofy to me. They could bore .25mm with their precision hone.

Ill see if I can send a guy over to help.

[LT80]

Here is a reply I got from a polaris mechanic:::

"Nope,wont work,or at least not for long... The cylinder is already worn down .004 over standard bore and I assume the stock piston is in about the same shape or worse. When the piston/cyl clearance gets around .005 they start rattling,then later on people wonder why the piston skirts broke! Can't do like they did on cars years and years ago and just use oversize rings. Plus it'd have to be honed down to even get the .010 oversize ring end gaps to work which would make it even worse on the stock piston to cylinder clearance. Lot of shaking and rattling would be going on and just plain wrong. Says he has to only go 800 feet to check the mail,but think he'd be walking about 600 feet of that when the engine goes south on him. He'd be better of just trying std rings and seeing how long it'd last. But sooner or later he's gotta bite the bullet and do it right,new oversize piston and rings,cylinder bore then he can go check the mail and maybe even go a little further... "

I understand money is tight but to do it right is about $175. more (115 for the piston/60 for the bore) than youll have in it anyways.

[dew2]

Well hey I sure do appreciate the feedback.This is the only answer I received from 3 sites.It does sound like excellant info.So thank you I have the cylinder cleaned up crosshatched and 2 sets of rings on the way.