You can jump start the bike, but from what I've seen in print, if you use the battery from another vehicle, you may want to just do this with the vehicle not running, maybe too much current for the bike to handle, don't really know, I don't have any first hand experience .
If the battery voltage is down in the 9-10 volt range, the electronic ignition won't work if you try to 'bump' start the bike, you may be able to with a contact breaker points type ignition like the '78-'80 bikes have .
If your battery is low on charge, you're use of the bike may be the cause, the charging system on our bikes, really don't do too much to charge the battery, below 3500 rpms .
So, if you ride in 'city' traffic, lots of traffic lights, you pretty much aren't charging the battery .
Check the charging system to see if it's operating correctly, with a fully charged battery, above the 3500-4000 rpm area, you should get around 14 volts, the regulator is set for 14.2 volts .
Checking the fluid level in the battery cells is critical, if you have a serviceable type battery .
Let the fluid level go down on one cell, where the plates are exposed, has pretty much doomed the battery to a shorter service life .
If you do add water to the battery, use only distilled water or RO water (water run through a reverse osmosis treatment system), unless you're out in the middle of nowhere, then you need to do what needs to be done to get you home .
I'm relatively new to battery maintainers, but I am sold on them now .
I put one on whenever the bike is parked for the day in the garage .
This is especially important if you reside in an area where the bike is parked for the winter .