Detached carb, reattached, now hard to start. Reasons?

[RobH2]

I simply detached my carb and lowered it down. I placed a piece of paper towel in the throat to stop debris.

Then, I replaced my manifold gasket. I reattached the carb.

The engine is now extremely hard to start. After 4 or 5 grinds for about 3 seconds each, it will catch and runs great a full throttle. But under about 1/2 throttle it shuts off.

Once warm, it seems to start better but is inconsistent. Even warm, sometimes it is very hard to start but eventually always does.

I'm trying to diagnose and figure out what could be causing this.