Engine has stopped working!!!

Hi guys.
I recently installed my little 50cc onto the pushie. It was going great for about a week (with a couple of hours of solid riding on it) but then it gradually died. At first it would just not give power when i gave it full throttle, then it gradually got worse, conking out when i gave it about half throttle.

Then today it just stopped giving any power. It will kick over and start when the choke is in, it will idle like this also. But when i depress the choke i loose all power and gradually come to a stop.

A few things about the bike. The spark plug was oily black, does this mean i have a serious air leak or something? I recently took apart the carby to check if it had junk in it (when it started loosing power) but found nothing. I am using 20:1 fuel mixture. I assume the spark plug is working fine as it still idles using the choke. I recently put some gasket sealant stuff on the exhaust gasket as it was leaking fuel (could this have got into the engine and stuffed it?). And for all those people who have no confidence in me, yes the gas is turned on and it has fuel.

Any help would be appreciated. It is frustrating as i just had it going great.

Boz

worked it out guys.

pulled the carby apart and that pole in the fuel bit (sorry about the terminology) had unscrewed.

purring like a kitten now.

got pulled over by the cops as i was test driving it though. they said it was totally illegal and i said in NSW (Aus) it is legal as a power assisted bicycle if the engine is under 200 watts (i think my 50cc is more like 1000 watts, oh well). they looked stumped and let me off with a warning.

cheers anyway, boz.