I suggest you check the oil for gas mixed in there. It sure sounds like the floats are leaking fuel into one or more cylinder. Wet plugs won't discharge a timing light as they represent a dead short to ground. Starts and runs fine the rest of the day. Ok so it isn't leaking that bad but it's leaking.
The only way to prove or disprove it is to let it sit overnight. Before attempting a start remove the plugs and check for wet with gas. If not plug them into the plug wires and leave them touching the heads. Then crank it.. I'm betting a fireworks display will result as each of the cylinders pushes the raw gas out through the plug holes and is ignited by the spark plugs.
Another hint was that you said it cranks then hydros slightly. If it were hydro locked you'd notice it on the first 2 revolutions at most. What you are probably hearing is a flooded cylinder dieseling and fighting the starter.
The person with the most toys wins!
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1984 GL1200 STD
2010 HD Ultraglide Classic Limited
Previous bikes:2001 GL1800, 2000 Dyna Super Glide, 1972 CB350 K4, 1985 GL1200A, 1997 1200 Sportster, 84 GL1200I, 82 Honda CM400E, 81 Suzuki GS650L, 72 Triumph Bonneville 750, 72 Honda CB350, 66(?) Honda 305 Scrambler, 6? Yamaha yz250, 62 750 Matchless (Norton-Villers).
My other 2 Goldwings.... Yeah it's MBS..