First Time rebuilding top end, Whats up with this? Replating needed?

[joeym4130]

Hey all, rebuilding my top end on my 2smoke RM250. Was gonna put a new piston and associated parts in to 'freshen' it up.

First time, but diassassembly was cake, i love how easy these are to take apart! I just don't know what things are supposed to look like, so i came for assistance :worthy:

Check out this picture. What is the cause of this in the cylinder, if it is a cause that is pinpointable?

The pics make the scarring look much deeper then it actually is. I can barely feel the mark with my finger, but i CAN tell it is there. Does this mean I need to send it to be replated? I dont want to use this if its going to eat up the piston in a month, but I dont feel the need to do it if its minor enough to not be a problem.

I also threw a pic of the old piston in too, in case something is up with that



Thanks for the tips!

 

[Aftermath]

If you are going to do something, do it properly or don't do it at all - applies to bikes as well. Looking at the photo's, I personally would plate your barrel and re hone it. Actually my barrel is getting re-plated as we speak. Should get it back tue - wed. Piston broke in half on a 04 YZ 250 and scarred the barrel a bit. Not going to take any chances.

 

[joeym4130]

Think something got in the motor?

The previous owner had an old ratty filter on it. I just was wondering what could have happened to do this, I thought the piston would be messed up too, but it looks ok to me. The mark on the piston top is from my nail scraping the carbon, its not a crack or anything lol.

 

[MXP1MP]

That looks like sand particals/ dirt maybe some very small rocks I don't think replating it is going to fix that alone it looks to deep. I would big bore and replate it.

 

[joeym4130]

K, thanks. Damn that kinda sucks. I'm gonna call up Millenium Tech and see what they can do for me.

Should I just go take apart the bottom end too?

Weird thing is that it was running really great just was hard to start in the cold. Sigh.... haha

 

[dan druff]

K, thanks. Damn that kinda sucks. I'm gonna call up Millenium Tech and see what they can do for me.

Should I just go take apart the bottom end too?

Weird thing is that it was running really great just was hard to start in the cold. Sigh.... haha

my old cr had a huge chunk around one of the ports missing and millenium tech did an awesome job, plus incredably quick turn-around. you can also order the prts needed for the rebuild from them too. replating will fix that.