Bubble aside, what issues are you having with it? The bubble itself is irrelevant.
The bike will only need 5 things to run:
A decent spark - are you getting one?
Air - Is this clear for air in and air out; filter, exhaust; vacuums?
Good Fuel - Is the spark plug wet and does it smell of fuel?
Compression - Thumb over the spark plug hole is the crude method of judging this.
Timing - has this been checked.
With all of the above the bike will start, it may not idle, rev or run right, but it will start.