Check ignition timing.
Disconnect the vacuum hose from the sensor-distributor.
Connect a phase shift stroboscope between the high voltage wire of the 1st cylinder and the tachometer.
Taking division 0 of the ignition angle setting scale as a reference point, check the characteristic of the centrifugal regulator according to the graph given in subsection «Detailed Specifications».
If the characteristics differ from those given, check the ignition distributor on the stand.