well the magneto or rotor or flywheel call it what you will is keyed onto the crankshaft via a woodruff key if this shears and it slips it will put the timing out so check it hasnt sheared.also the cdi units on some of these chinses bikes do have a tendency to play up as the capacitors inside them tend to change their discharging values and of course if they discharge too early or late it will affect the ignition timing.
adam bike doctor, August 2010
