21 hp B&S Flathead Help

How's it going, I'm new here and wondering if someone can please help me with this problem, I cant seem to solve.
So I have an Old tractor I picked up from some guys grave site he made for it in his backyard, decent deal. He informed me he lost spark several years ago and never had time or the effort to fix it.
So I brought it home and the fun began stripped it down found the initial problem being the coil, bought a new briggs coil and she was back to life. For a second ......
 
Then the hard starting began. Its got way to much compression , I thought for sure something to do with the decompression system. So the tear down began, so far I have re seated and gapped the valves, full carb rebuild, full gasket set and seals, completely tore down the motor and cleaned everything, put it all back together still hard starting, everything seems fine inside.
Starter seems strong, just not strong enough to turn it over to full potential. sometimes it will spin fast like its supposed too, but 98% of the time, it will act like the decompression mech isnt working. I'm torn with spending more money without pin pointing the problem. 
 
Any old B&S gurus out there that have any idea what i could be missing please help me out.
 
Thanks