How do you remove the blade adapter from the Crank shaft on a Model 917.378900 7.0 Horsepower powere porpelled rotary lawn Mower?

After removing the center bolt that secures the blade the blade adapter is just a slip on piece that has a key.

However, most Blade Adapters will be somewhat rusted on. It is advisable to apply a penetrating oil such as Blaster or Corrosion X on the shaft and allow it to run down into the adapter for an hour or so.

If necessary you may have to use a puller to remove the Blade Adapter. If so, it is advisable to use a longer bolt that bottoms in the engine shaft or some other means of keeping the puller screw from damaging the shaft threads.