This GMS 40 needed the rear bearing replaced this spring. We opted to replace the rear and front bearings.
When I removed the front bearing I discovered that it was shielded on one side, but not sealed. The shield does nothing for this bearing as it is behind the drive washer. It results in a very significant air leak. The air will go through the bearing as fast as you can blow it through. It is no wonder that this engine wouldn't shut off and was sometimes tempermental to tuned.
I put a sealed front bearing in. No shields. I left the outside seal intact and cut a small slit in the inside seal so some oil could get to it. The sealed bearing made a huge different on this engine. There is no longer a major air leak through the front bearing. The engine is now super easy to tune, very reliable, and yes it does shut off when you chop the throttle closed.
If anyone is having tuning problems with their GMS 40-47, or that your engines do not shut off and you have corrected all other potential sources of air leaks (carb and back plate) -- just replace the front bearing with a sealed bearing.
TTFN!