I ran my Poulan 305 Pro for the first time yesterday and it ran fine, but it seems to develop a lot of play in the crankshaft bearings after it warms up. The play seems to go away again when the engine cools down. These are new main bearings that I got from Poulan. Could it be they are not a quality bearing? Would replacing them with a ball bearing of higher quality be a cure for this problem? The bearings fit tight on the crank and I used bearing mount in the case recess as I thought the fit was a little loose. I have not run across this problem before. Any ideas, guys? Thanks