If I am on a student visa in China when it expires can i renew with a Tourist L here in China?

Yes, you can apply from local PSB, but make sure to provide flight ticket and hotel reservation for extra stay. The application should be submitted 7 days before the current one expiration.

sorry but what flight ticket - im already here in China on a student X. and havent needed a flight ticket to leave for the original one.

Yes, but you need to provide a ticket with confirmed date for leaving if you want to extend it to tourist L, as well as hotel reservation. Sometimes, you may be required to show financial support as well. Generally, they want to see a bank account with at RMB 21,000 for extra 30 days.

it doesnt make any sense to me to 1 week before my X type runs out go and by a plane ticket to leave in a month or two months when i dont know if im geting it or not and if i dont want to fly from there - maybe i will go out by train from Kashgar.