peugeot vivacity 50cc will not start?

Im pulling my hair out with this bike..... Its my daughters bike and it was running fine, then for no apparent reason it just didnt want to start.

Iv cleaned the carb countless times,
New plug,
Even took the head off, and replaced the piston rings, good compression.
Sparking so so.

50% of the time its goes to start for a secound or two then dies.

Can somebody tell me what the electic componant is on the carb please and can i test this in anyway.

Its due to go in the garage this wednesday, but if some kind sole could help before, that would be good.

Many thanks in advance

Dave

Please feel free to email if you wish.

Dave@wend222.wanadoo.co.uk