1450- New to me, won't start. Pulling my hair out!

[sgt.porter]

I bought a 1450 this weekend. It was 2 1/2 hours away, but a decent deal and I've been wanting/needing something with a hydraulic lift (for tiller, blade, etc..) for a long time.

I get to the place and find out the guy is a recently retired International dealer, had rebuilt and over-bored the engine himself. It supposedly had about an hour of run time since rebuild. I drove the tractor around a bit, felt real good about the deal, loaded it, blade and snow blower on trailer, and happily brought it all home.

At home, I use the tractor to pull the blade and blower off the trailer and to the barn, put the deck back on, fire it up again, start the deck up, it mows about 10', it bogs down, backfires a couple times, and dies. I start it again, start the deck, same thing, bogs down, backfires, and dies. Start again, try to make it to my shop, backfires multiple times over about 20', dies, never made it to the shop, wont start at all now.

I pulled the side panels and air cleaner off, notice immediately that the carb is spitting gas while I turn it over. I remove the carb, take it to the bench, disassemble, nothing noticeably wrong, give it a good cleaning, make a slight adjustment to the float, factory set the needles, and put it back on.

Now there's no spitting gas, and after a few unsuccessful attempts to start, there's a fine fog of fuel fumes in the intake.

Here's a list of what I've done the last couple of days (In no particular order):
Checked for spark by laying plug on engine and cranking over (multiple times, and after every major change).
Ensured there was no arc at the points (multiple times).
Set and checked the timing by static timing method (checked multiple times).
Ensured 12v running to coil with key on.
Tested coil resistance (good).
Installed known to work coil from my 680.
Tested for continuity of spark plug wire (had some resistance, replaced with good wire).
Installed known to work condenser.
Watched through intake port and spark plug hole to ensure valves are moving correctly (they seem to be).

No matter what I've done, I get the same scenario. Engine cranks just fine, sometimes sounds like it's firing, sometimes puffs a little white smoke from the exhaust, has a fine fog of fuel in the intake, with no excess fuel build up that I can see, but still won't start at all.

I'm already admitting that I've been had by this supposed expert. But I took the deal, so I'll deal with it.

I don't know a lot about these engines, but I know enough about engines in general to guess that it's boiled down to a compression issue.

What's next? Do I need to tear apart this fresh, dealer rebuilt engine? Start with the valves then check the piston rings? Or is there something obvious, external, that I'm missing?

I own 5 Kohler K series engines, and I've never had this problem, and never had to do any internal engine work.

Thank you in advance, any input will be greatly appreciated.