Pick up on Eday OEM 4th over 1.0 piston and rings, going to take piston and cylinder for bore, my question is I was test fitting rings, bottom seemed ok, but seems like top ring will Need a lot of filing when compressed to pin alot of ring is out of groove, first DT for me, thanks in advance

Hi ... Welcome to the forum

Try flipping the top ring over .... You might have it on upside down.  ???
Seems to be a common mistake ... you wouldn't be the first guy to do that..  

As ENDURONUT says.
Tapered top surface. Keystone ring & groove to match. Should have the letter K somewhere on the piston crown to denote that fact.
If i'm wrong--umm--that makes two of us haha.
Welcome from NZ.
What's the bike in your profile pic?, looks like my old RMX250.

Old stock from ebay, just want to make sure they are correct, again could file to fit just want other eyes on these., Old bike in pic is an early 2000's Yamaha YZ 250 four stroke with yellow plastics, thanks again

Detective head on.

DT360 piston with dykes top ring?

Yamaha genuine pistons are supplied without rings, so someone has "put together" the set.

That top ring is far too big. DT400 maybe?

Dykes rings are low wall pressure rings and filing that much off will affect that.  Rings are not that expensive.  Far better to order the correct rings than try to make the wrong ones fit.

You do not need to send the rings with the piston for rebore, so ordering the right ones will not hold you up.

Genuine part number for the rings is 4451161040

Cannot get the ebay link to work, but check out:

eBay item number:364311232759

Screen shot of item number you gave me, same as one I bought, looks like dyke type also, you think somebody just mixed up my package of rings?

Yup.

Thank you, ordered set on ebay will send first set back

Are we speaking Dykes or Keystones?

cliff

Ok, i was obviously wrong on the Keystone theory.
Before you send them back. The Dykes Top Ring 'Doesn't' sit hard in the groove base plus sit hard up to the step at the same time--'doesn't happen'.
By memory there's a gap & theory being the gas gets behind it & pushes the ring harder to the bore for a better seal. Maybe i'm talking BS but sounds good lol.
I might have a kit to demo later to prove my theory==or not.