Motorcycle Repair: motorcycles, head gasket, dirt bike

Question
i have a 1972 kawasaki 100cc 2-cycle dirt bike and i have no clue how to set the timing ?
when i choke it it will start but only run for 30 sec why is this ?

ps i just replaced the head gasket  

Answer
Hi Andy.
 My guess is that the bike sits in storage over the winter and/or doesn't get ridden a whole lot, like a newer, larger bike would.

 Start by getting the repair manual.  That will have all specs as well as directions and diagrams for setting the timing.  You should do a full service tune-up (timing, valves, etc) anyway.

 The pull the carb and clean it properly.  It probably has a huge amount of residue build up in it.  drain and reseal the tank and replace the fuel line.

 Once that is done and everything is reset, including the idlespeed, which could be off, then it should run like new.

Good luck.
FALCON