Mower blades keep turning after PTO engaged on Agway 11/38 rider?

I'm having a problem in that the blades keep turning, at a slower pace, when the deck handle is pulled back to the dis-engaged position. I have replaced the switch with same part MTD 925-080C3 but no help. I checked the switch with ohmmeter and confirm operating correctly. I'm also having a great deal of difficulty in starting the mower and thought that the above problem may be related. I have rebuilt carburator, changed spark plug, air filter, fuel filter, battery, & flywheel key checked good. I have to use a battery charger in start engine mode to finally get it going, but once started the mower runs great and idles well also.. Does anyone have any suggestions.

Thanks,
Peter