Small Engines (Lawn Mowers, etc.): cub cadet starting problem, hp motor, cub cadet

Question
My mid 80's cub (model 1812) with the Kohler 18 hp motor is hard to start when its cold (below 40 degrees). I put in new plugs but it still wouldn't start.  I took a plug out and cranked the motor while holding the plug next to a bolt on the motor.  The spark was very weak.  I can see where that could possibly be the problem.  My question is this; what component sends the spark to the plugs on this engine?  And do you think this is the problem?  Thanks.

Answer
the ignighter coil under the flywheel. and maybe your oil is too thick. make sure your using proper oils. is battery up to full power?  if not i,d replace with heavier cranking amps.  also is starter to you seem  to be working? alot depends on your problem. one at a time i,d check it over and go from there. may want to try  new plugs.