PISTON DAMAGE PLEASE HELP

[Cr125zrule]

hey guys...when i striped my bike down the ring was broke in 3 places and bent back on its self.....the piston had extremly bad scaring to the rite side (rite side if u had the arrow pointin towards u) did not damage the bore tho...but i would like to know wat caused this as i dont wont to put my new wiseco piston kit in if im gonna start it and it do it again (it was a new ring on old piston...and yes it was correct ring and im 99% sure it was broke in properly.....any help wud be great as i dont wonaa faulk out another £70 if it does it agin

[crdemon]

wow, ur piston was that bad and ur cylinder wasnt scared? that really sucks, can u wiggle the piston at all? mabey crank bearings? Do u let you bike warm up before revving it out?

[TRXman86]

it may have just been a bad ring. even thought it was new, it may have been a bad one that got thru production. sort of like whats going on with the new trx450r models. frames are braking and a-arms are junk. just a bad set that got by inspection. and it also may have been just a little dirt that got in. that would help a little. i think anyhow. hope it dont happen again

[Cr125zrule]

ok thanks...so i just wack my new piston in yeah

[crdemon]

yep pretty much, sounds like a good plan.

[Cr125zrule]

wat i ment is if i put a new 1 in it wont just do it agin

[Faded]

Did you set the ring end gap prior to installing the rings?

[YZ pilot]

What brand rings ?

[crdemon]

Originally posted by Cr125zrule
wat i ment is if i put a new 1 in it wont just do it agin

just joken, didnt mean anything

[Cr125zrule]

its a wiseco prolite kit.....

[tons_of_fun]

You could have put the ring in wrong, or was it the stock top end?

[redeyemindtrick]

even if the cylinder isnt really hurt, you need to hone it with a ball flex hone. if it has any vertical scratches at all, the new rings will wear into them, causing loss of compression. using the hone will make a criss cross pattern, and will allow the rings to seat more properly. smearing 2-stroke oil on the cylinder walls is also a good idea. it is very important that the ring gap is set in the right spot, if the ring end is set over the guide pin wrong, it can easily cause your damage. hope any of this helps you out. good luck

[Reuel]

If the ring is bent back on itself then, it sounds like the piston/ring was too small or the bore was too big. There just is not enough room for a ring to do that if everything is the right size. Mic your bore and mic the piston. Make sure they are the right size. Check the ring end gap. If you don't have the right tools then take it to a shop and ask them to check the fit.

[kuritaro9]

could be that the locating pin was damaged or the rings were installed wrong. i know oem rings have a (N) stamped on them, that needs to face upwards.in mot sure about the wiseco kits though...i agree with faded about the ring gap measurement...esp, if its on a older bike with a somewhat worn bore.im assuming of course that this was for your 92 cr....

[ossagp]

Go with what Reuel and Faded suggested. An easy way if you have no way to measure (ie an inside type micrometer) is to place the ring in the bore and use the piston to push it up and down, (faced where the ring would be located on the piston pin so you dont snag it). (This is assuming you have access to a ring and piston,,if not off to the shop to get it measured.)Move it up through the bore,,,the two ends SHOULD NEVER TOUCH, the narrowest measurement and the widest will be available from the ring supplier or the OE manual. Usually .012-.022. But check that to be sure. Wiseco will tell you.

Your bearings could be out on the cranshaft as well. Remove the ignition cover, grab the rotor/flywheel and pull up and push down. If you feel any movement, it is too much and the bearing should be replaced.

I don't think I would chalk this one up to a bad ring.

On reassembly, I have the best luck with a dry cylinder,,just enough oil on the rings to keep it easy to assemble into the bore if you must. (mine go together after being cleaned in hot water and soap, with a hot rinse).

[thermox]

I'd make sure that your cylinder isn't scarred, if your piston is that bad your cylinder most likely is too, maybe get a second opinion?

[scotsguy]

Sounds like the powervalve has made contact to the piston, would check it all out before throwing a piston back in and doing some serious damage.