motor problem 21 k&b

[NAMBA860]

Hi to all and all the best to everyone for this new year,anyway my k&b 21, idles fine ,1/2 trottle fine,3/4 fine,but as soon as i put to full throtle goes for couple sec and stops,any ideas thanks,peter.

just looked at mine and the crankcase is cracked threw the bottom check yours there also.