I just walked in from the garage where I currently have the head off of my '85 ATC 250R. I took the head off because I notice a small coolant leak coming from the back of the head when I really had the throttle pinned. I was going to just replace the head gasket but now I'm not sure if I should just go all the way.

The top of the piston is black with a lot of carbon deposit on it. I can wipe black soot off the top of it. I believe it is due to the last owner because he ran it at 20:1 with a synthetic oil which in my opinion is way too rich. I further believe this because the plug that was in the bike when I bought it was black and oily. I then changed the mix ration and jetting and the plugs are now cocoa brown.

The question is, should I put in a new piston/rings? Should I also bore the cylinder to make sure I have a good fresh cylinder?

Opinions would be greatly appreciated!

 

put the cap back on and ride it, if the prev owner was running 20:1, there should be lots of rings left, unless the bike had no comp before, i would say its fine. you can always rebuild it later after u ride it.