I think it is an emissions rating. The wild thing is a newer design and has a cleaner burning engine. The 4620 will just blow dirtier exhaust sooner than the Wildthing. I am pretty sure with a little care and tuning they will both last a good long time. :msp_rolleyes:
I am pretty sure all my saws would fail emissions testing within a few minutes of operation....just as soon as I richen them up a tad to make them live a good long dirty life. :msp_scared::msp_scared:
I think the EPA would like for every saw to run so lean as to not leave any emissions but burn up a piston every time you use it..