Small Engines (Lawn Mowers, etc.): older craftsman riding tractor 12.5hp briggs intake vavle stuck open, safety switches, vavle

Question
i have an older craftsman garden tractor and she wont start
12.5hp briggs flat head intake valve  stuck open does go down if i tap wit hammer when at tdc but wont go down by self? did try lube it like crazy and carb cleaner no luck on self going down.  
Was sitting for 2 years ran when put away did changed oil cleaned carb changed filter cleaned valves without taken em out cleaned head motor does spin by hand and by starter but starter does only off jumping starter not key.   Decks up I'm on seat trans in neutral are the sensors stuck?  Trans is a stock 6 speed looks to be peerless stuck but kind of moves after wd40 lever area  very hard??
  Any suggestions,
Thank you ,
  Leonard

Answer
You may have to remove the valve and clean the valve stem and intake valve guide.  Use lots of lube and carburetor cleaner when removing the valve to prevent damage to the valve guide.  If you damage the valve guide you can always install a valve guide insert.

As for the starting, do you have a multimeter to verify/check the safety switches are funtioning?  The switches are simple on/off switches, like a house light switch.

Let me know if the intake valve frees up and if the safety switches are functioning.

Eric