Small score mark in cylinder

[Little Jeff]

I have an '02 KTM 300EXC that I rebuilt from the ground up pretty much. Cylinder was replated by Millenium Tech and sized to piston I sent them. Went through all the heat cycles, running 40:1 conventional 2 cycle Honda GN2 premix for the first tank to seat the rings. had to pull pipe off to reseal it to the flange on cylinder, bad design:banghead:. So I decided to look inside the cylinder and noticed a very small vertical score mark on the intake side of cylinder. I'd say less than a 1/16" wide. I made a little poker out of some welding rod and really couldn't feel the score mark. I'm thinking that is where the piston ring gap is but can't remember for sure. Maybe some one can confirm the ring gaps are on the back of the piston. I can't take a pic as it was to awkward to even try and get a pic let alone getting a small flashlight up there. Anything I should be worried about? I resealed the pipe and was planning on riding it this weekend. Thanks

Little Jeff

[rpt50]

Looking up through the exhaust port can play all kinds of tricks on your vision. Pull the head off and take a look. The rule of thumb I have always followed is based on the "fingernail test". Any scores or scratches you can't feel with you fingernail are not worth worrying about. At least that has worked for me. If you can feel it, you might want to send it back to Millennium to let them have a look. A proper hone might clean it up.

[Gary jp4]

And yes, the ring gap is positioned at the rear of the cylinder.

[Gary jp4]

Gap or Gap's

[Little Jeff]

It is a 2 ring piston if that was what you were refering to (gaps)

Little Jeff

[Gary jp4]

Yes. I was just adding to by previous post that weather it is a one ring or two ring piston the gap, or gaps, are both located and pinned in the back. With the two ring set up they are only staggered slightly.

Gary

[Rip Wheeler]

I have an '02 KTM 300EXC that I rebuilt from the ground up pretty much. Cylinder was replated by Millenium Tech and sized to piston I sent them. Went through all the heat cycles, running 40:1 conventional 2 cycle Honda GN2 premix for the first tank to seat the rings. had to pull pipe off to reseal it to the flange on cylinder, bad design:banghead:. So I decided to look inside the cylinder and noticed a very small vertical score mark on the intake side of cylinder. I'd say less than a 1/16" wide. I made a little poker out of some welding rod and really couldn't feel the score mark. I'm thinking that is where the piston ring gap is but can't remember for sure. Maybe some one can confirm the ring gaps are on the back of the piston. I can't take a pic as it was to awkward to even try and get a pic let alone getting a small flashlight up there. Anything I should be worried about? I resealed the pipe and was planning on riding it this weekend. Thanks

Little Jeff

Yes, this is where the ring gap is. If you cant feel it, I wouldnt call it a score more, more like a wear mark. And shouldnt be an issue.

[Little Jeff]

Cool, Thanks for the replies guys. I'm riding it.

Little Jeff