The hole is just to let any condensation out.
Two things that cause a jerky feeling at low revs.
The most likely cause will be that the bike is in good need of a carb balance, which isn't the most terrible of jobs, but only if you have the right equipment which i'd imagine is highly unlikely unfortunately.
http://foc-u.co.uk/index.php/topic,91.msg160372.html#msg160372A faulty or offset TPS can also upset the feeling of the bike at lower revs too. I've had 2 go wrong on my bike so i tend to know the symptoms now, even if it's just offset.
There is a simple check you can do in a few seconds, but to adjust it if necessary then a special Torx 25 security screwdriver will be needed.
The TPS is the little black plug in gadget sitting on the right side of your carbs.
A quick check can determine whether it needs adjusting, or maybe faulty.
Bear in mind though, to do a decent carb balance, your carb screws must all be set equally, your air filter must be clean, and your TPS needs to be funtioning correctly, although checking it is actually a part of the balancing procedure as well.
http://foc-u.co.uk/index.php/topic,13864.msg156715.html#msg156715
