Alternator (actually just an extra coil on the magneto stator) has an output of approx. 350mA, and will recharge a battery after a 30 second start cycle in approx 20 minutes at full (
Phil Saunders, September 2010
Thewre is a very small alternator which does give a small top up charge as the engines running, but will never put back what you take out to initially start it. If it's not holding charge and the battery is over three yers old then replace it.
