My 509 is in the shop right now for the same reason. Not quite an 1/8" groove (caught it before it got that bad) but definately the same situation. Did you crack the head as well? I did. It all depends on how severe it is. Sounds like it can be fixed. Where are you located? I can recommend a good shop to get it done at. Oh yeah, plan to go to a larger piston too. My deal was caused by bad gas that sat in the tanks for over a year outside. I was going to drain them but just added some 110 and thought it would be OK, expensive mistake!!!