You've got your carburetor tuning issues causing your problems. The "needle" that is attached to your throttle slide does nothing until you're at about 1/4 throttle. It does not affect how the engine starts. That is handled by the fixed jet in the bowl, and is smoothed out by the air bleed screw- which really doesn't prevent it from starting either.
Studemann had it right in his first post, raising that needle causes the engine to run more RICH, more quickly. You also said it right, because you said "raising the clip" which means "lowering the needle." The needle is sitting in the main jet hole, almost blocking fuel from going through it. As the throttle is applied, the needle lifts out of the hole. This allows more fuel to flow through that main jet. The needle does most of the "tuning" from about 1/4 to 3/4 throttle, but at wide open throttle, the needle is completely out of the hole and it's all main jet.
Your problem right now is not your needle, because it has no effect on starting the engine. Adjusting that needle is only done once the engine is starting correctly, and once you know you can achieve wide open throttle under load. (Never run these at WOT without a load)
Since you had fuel running into your intake manifold, it means you seriously flooded the intake by repeatedly trying to start the engine, and/or your float is not adjusted to 24-26mm, or the float needle seat is leaking. Again, Studemann probably called it right- that excess fuel is hydro-locking the piston. If the float is set too low, (you set the height with the carb upside down,) the bowl will over fill with fuel, sending raw fuel into your intake.
I highly recommend reading
Ian Williams Tuning article on Mikuni tuning. It's an easy read and explains the concept of operation of these carburetors as plainly as I've seen. Once I grasped the concepts there, I found that tuning these carburetors was very simple, but you have to take it one circuit at a time.
One final note here, is that plugs can become fuel soaked and stop working, even after drying out. Take nothing for granted.