RE: Pull starter slipage proublems!
another thing that works with my older nitro truck motors is to spray a little WD40 down the pullstart where the string goes in. This degreases the one way and it grips the shaft and voila! engine starts. Also storing your engine with with pullstart higher than the crank case stops the fuel from sitting in your one way and making it slip, especially if you are using high oil content hobby shop fuel.
Ben