I've fixed the loose bar problem on a Husky 55 Rancher (see earlier post below), but while putting the piston stop in I noticed that the top of the piston has a pretty substantial carbon deposit on it. Then while starting I found it is extremely hard to pull when starting, although once started it runs fine. The plug was clean as was the spark arrester, although the owner had the saw serviced prior to me seeing it so these items could be new. My question--has the carbon deposit built up enough to block the exhaust port and thereby making the compression so high. Or has the deposit built up enough on the cylinder walls to make piston travel more difficult? I don't think the owner willl pop for a dis-assemble and clean (He pretty much hates this saw) but I'm still curious.