You're forgiven - only one in a 100 ever come back to report success or to say thanks - so no matter - and you've been courteous so thanks for the thanks...
To follow the link - highlight it and type the character C (for copy) as you hold down the control key.
Now in a search engine address bar - type Control V (for paste)
And follow the link. (Copy & Paste using Ctrl C & Ctrl V)
I know nothing of scooter engines but what you describe sounds like an auto choke unit....
http://www.pedparts.co.uk/blog/automatic-choke-unit-50cc-mopeds
The carb should not behave as you explain - sparks to the chassis - I would guess the auto choke unit to have a fault and to be shorting battery +ve to the carb body.
Amazon sell an auto choke unit for £4.03 - carriage free!
ZY Gy6 Scooter Carburetor Electric Choke Moped Atv Quad Go Kart 50cc 125cc 150cc Carb
I ride a Honda MSX 125 but do not do maintenance on it.
For £7.28 you could have both a manual and an auto choke unit!
Happy fixing...
January 2015
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix motorcycles.