Wats the most ccs a learner motorbike rider can have? i weigh 54kg and i am 168cm tall?

If you're in Australia, it depends in which State you live. In some States it is 250cc but States like NSW (and soon Victoria) have LAMS which is based on a power to weight ratio and you can ride up to 650cc dependng on the bike. Check with your local roads authority - in NSW the RTA web site.