The Phantom 85 motor that I think he mentioned he has is NOT nickel plated inside the cylinder, it has an applied ceramic coating inside that cylinder as stated in its description on bicycle-engines.com as well as the fact that I have a P-85 I ride and can attest to this as I observed the coating when I put mine together.
Hopefully the OP has been running that according to instructions using a 20:1 mix for 300 mile breakin period using Conventional oil ONLY, and then no less oil than a 25:1 mix after breakin and of course thats when synthetic oil CAN be use, but only after conventional oil breakin first.