Did you pressure test it after assembly? I am very unhappy with the 660 nikasil cylinder I got. I will wash my hands of them if they don't make it right. I was the only huztl solider who saw benefit in them.I just ordered the 660 big bore kit and hope it comes in niksel. Kind of funky I started it today to cut some wood and it was idling very high and I tried to adjust it down. It all at once idled down after turning it all the way down. I turned it back to where it was and the saw will not start. I changed the plug, no help. I squirted some fuel into the carb and it would start on that fuel and then quit. I pulled the carb and cleaned it but it was not dirty at all. Could spray threw everything. I am wondering if maybe one of the crank seals have gone?
The kits they sell normally are chrome they had the one I purchased label nikasil on eBay.
It sounds like a leak. I had a big leak and it would not start no matter what I did. My first kit was a real lesson. Bought me a tester and never had that issue again. Just too many ways for it to leak. Soapy water under pressure is amazing. Like an old pointer dog.