What do you think about this cylinder ?

[Henrii]

Hey All,
I would have liked to have your opinions.
I just started to open the motor of my 1986 ATC 125M and this is what I found: the cylinder was marked by the rings. Apart from that it looks good. I do not have much experience in judging whether a replacement or re-boring is necessary.



For the exhaust valve I ask myself less questions

[Ghostv2]

Piston wear is equally as important. Take a picture of the piston up so we can see if there's any slap, detonation, etc. Take a picture of the skirt if there's any wear.

You'll need some better pictures to even begin to get an internets opinion on the cylinder. Although I'd just do some research and come to that conclusion on your own. I'm not even close to an expert myself.
How was the compression? How'd it run?

[atc300r]

Personaly Id do a valve job with new valve seals and new oversize piston kit.

[Henrii]

Piston wear is equally as important. Take a picture of the piston up so we can see if there's any slap, detonation, etc. Take a picture of the skirt if there's any wear.

You'll need some better pictures to even begin to get an internets opinion on the cylinder. Although I'd just do some research and come to that conclusion on your own. I'm not even close to an expert myself.
How was the compression? How'd it run?

The cylinder is glued well I have not disassembled it yet. I do not test the compression but the motor run well but I did not run it more than 5 minutes after unlocking.

[350for350]

I'd agree with atc300r. This is the only way to be absolutely certain that everything is new. I think that the exhaust valve has a lot of carbon buildup on it. I could be wrong, but I think that when there are marks left by your rings like that in the cylinder, then it has enough wear to need to be bored to the next oversize.

[yaegerb]

X3....bore for next piston size, new valves and valve seals.

[Henrii]

Thanks guys for sharing you opinions :-)

[HoldMyBeer]

125m? Wire brush, honing tool and a set of rings.

[Henrii]

Finally found a 1987 TRX 125 cylinder in good shape, no ring marks, scratches or rust in the cylinder and also ordered NOS rings founds on ebay.
Currently cleaning the cylinder and cylinder head :