N-Zeta 501/01, Workshop Manual

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If the driving gear with hub or the seal are not to be replaced, the gearbox sprocket
need not to be removed before separating the crankcase halves. Remove the gear
change shaft, the selector fork guide rod and the gears with shafts. Slacken the four
screws holding the cam plate to the LH crankcase and remove the cam plate. When
refitting the cam plate, take care to locate the stepped screw in the central position .
Now drive the crankshaft assembly out of the LH crankcase half.
To refit the bearings into the crankcase, heat the case to 80ºC / 176ºF preferably in
an oil bath. When dismantling and reassembling, the circlips securing all bearings
must not be forgotten and omitted.
Dismantling The Crankshaft Assembly
The crankshaft assembly should only be dismantled in a specialist workshop
equipped with a hydraulic press capable of exerting a pressure of 3,500kg to 5,000kg
/ 7,700lb to 11,000lb pressure, a measuring table with centres and indicator dials.
The job should be entrusted to an experienced engineer. When pressing the
crankshaft apart, care has to be taken not to damage the left thread on the pin. Care
should also be taken not to alter the position that the pins were pressed together. Of
particular importance is the position of the RH crankshaft pin in which there is an
opening for the rotor locating pin. Wrong assembly of this pin will result in incorrect
alignment and affect the ignition advance. As stated above, the crankshaft assembly
should only be repaired by a service workshop familiar with this type of engine.
If any parts, i.e. the connecting rod pin, connecting rod or its rollers are to be
replaced and if the complete unit is not being changed, it is necessary always to fit
only parts of the same grading according to the assembly table. For models 501/00
–
501/04, complete crankshaft assemblies of the ČZ 350 and 450 motorcycle models
can be used for replacement.