Briggs Stratton Lawnmower engine 17.5hp

Hi all, 
 
Some help would be appreciated here. I am coming from a place of trying to learn, but so far being unsuccessful in getting this engine running. 
 
Initially, the engine would not turn over, it just turned a bit and then got stuck. A google search led me to change the camshaft through this video (). That did not work, so I also changed out the battery, carburetor and spark plug. I could turn the motor by hand, but it is hard work. If I remove the metal cover at the front, I see the springs and rocker caps alternate movement and get decompression. 
 
I then noticed the positive wire on the battery was getting warm, as well as the wire to the starter. So I figured maybe the motor was bad and drawing too much current to try and turn. Changed the starter motor out. 
 
Now the engine turns better, but then gets stuck and will not fire. video is here () Spark plug gap is set, and it looks like fuel is getting to it. 
 
Any ideas from here would be welcome, and much appreciated. 

Sure - its on a Toy-Built Pony riding mower. 
 
The engine model number is 31C707, Type 3346 G2. 
 
Does that help?
 

What you may want to do as well is get a known good battery and wire it to
the starter DIRECT so your by passing your battery, possible bad battery cables, etc.
 
You'll have to touch a fairly HEAVY GAUGE wire between the positive line between the battery and starter.     If with the above, ^^^, and the starter is good, and still no crank, your probably looking at a bad camshaft.
 
You can also pull the starter and simply bench test it...
 
 
.
 
 

Your not going to hear the compression release.
 
It's a little pin, attached to the cam that bumps a valve open ever so slightly to release compression
ONLY WHEN CRANKING OVER.  Once running, centrifugal force swings it out and disables it.
 
Do you see a SMALL OPENING OF THE VALVE (I forgot which one) I think of the intake, 
BEFORE THE MAIN/FULL OPENING of the valve...
 
.