Gillera DNA 50cc wont start... help please guys

Hi Guys,
i need help, big time!
I have a gillera DNA 50cc (same engine as a piaggio or modern day vespa) i had it for a day and i noticed a loss in power especially on hills but it was not too bad on the flat. this got progressivly worse untill it only moved on a down hill or flat, i presumed this was my clutch so fitted a racing clutch. still the same problem.
so i have changed the piston ( i ensured the piston rings where the correct size using th barrel to size them. the arrown pointed down at the exhaust.) i also changed all of the gaskets. the piston is now in but i cant start the bike.
i am getting a spark from the plug, i tested it on the engine block and was geting a spark.
i put my finger in the hole and kicked the bike and it blew my finger out.
the end of the plug is damp with petrol.
the exhaust is kicking out pressure, so no blockage there.
the carb is sucking my hand in.
still it won't start. i have tried starting fluid in the manifold and directly in to the barrel from the spark plug hole. nothing. !
Could it be that the spark plug is not igniting enough ?
i have also noticed air bubbles in the main large petrol feed in to the top of the carb. but the bubble is not moving. does this mean the fule is not moving ( blockage in the carb? )

Please help it has stumpped me, !

 

just an update, i stripped the carb, it was full of petrol ( i presume thats normal) the small petrol pipe inlet was blocked so i free'd that up, the water pipe was clogged up so i unblocked that. none of which i woul think would affect the bike starting. there is only one thing left i can think of is changing the petrol all together.

any other ideas ?

 

thanks will do ill let you know how i get on.

 

hiya have u check u have a gd spark, as my dna had a spark but was not a great spark so had to replace the stator plate, the bloke from thre garage told me that dna are know to keep replace the stator plate.

 

ill give it a go mate thanks.