what do you mean the clutch slips? you shouldn't start the engine with the clutch in unless in gear but most likely will not start anyway. Make sure it is nuetral and just kick start it then with the choke on I ave the same engine aswell hope this helps...
try disconnecting the clutch cable from the engine and then try and kick it. If it works you know you have a stuck/stuffed cable, easy fix. Also check if the return spring is working... good luck.