If an engine has good compression, a good plug, and good fuel, it will start. If it's hard starting, something has gone off somewhere. Either it's not getting fuel, is being over-flooded, has compression loss, a bad carb setting, bad technique, and so on.

A bad idle can be traced to low compression, a bad plug, bad fuel, a bad needle setting, and so on.

As far as the bubbles in the lines are concerned, your note doesn't mention where they are, but if they're between the needle and the carb, it's the same difficulty that's been plaguing other modelers, and we've sent to O.S. all of the threads on the subject. They've told us they're looking into the problem.