On a previous post a fellow A.S. member said that sparks were caused by lack of lubrication. I have a PS7900 that never sparked before, installed a 32" bar to chew through some cottonwood, sparks galore, in oak it was OK. Are the sparks due to sand in the bark? A longtime wood cutter once told me that a sign of lack of bar oil was fine sawdust buildup on the side of the chain. There is no such buildup evident, but the sparks, coming mostly from the tip of the bar are unnerving. I certainly don't want to burn up a bar. Any thoughts as to the cause?