SO here is my problem, my Simplicity mower will not turn over. Bought it used and it ran great for a few hours, no issues except that the clutch/brake did not seem to engage, brakes didnt work and the really hard to shift gears. SO I parked the mower and tightened the nut around the spring like the manual told me too so my brakes would work. I turned the mower back on and the motor was loud and high pitched and sounded fast, so I dropped the throttle all the way down and turned off the mower, when I did this a big ploom of smoke came out of the exhaust. I backed off the nut some and noticed that now my parking brake was firm, the brakes worked and that it was really easy to move through the gears, (mower is off), when before it was very stiff to move through the gears even when off. I tried to turn over the engine, it tried and got nothing. DId it again and it made a louder "whirring/whining" type sound. I took out the spark plug and noticed oil on it and also oil on air filter. I let it sit overnight and this morning, same thing. Doesnt start, just sounds like something is spinning and goes "whirrrrr". There were no leaks anywhere. I figured being an older mower, a head gasket or something will need to be replaced at some point and have no qualms fixing it, just not sure where to start. Is it a head gasket? Is it a starter? Battery is new and belts are newish. Good gas and oil is at right level. Any ideas where to start? Thanks for the help.