Timing Gear Assembly
Incorrect fitting of timing gears will damage the pump.
Please read this section carefully.
The pump is supplied with the rotors set up so that no metal to metal contact occurs between
the rotors. When this was achieved each gear and shaft was marked with a dot punch, see
Fig 9b and 9c. The procedure for timing gear assembly is as follows:
1. Refer to the Rotor Assembly section for rotor and shaft keyway position.
2. Each shaft and gear spline is paired together by dot punch identity marks,
for example, two dots for both drive shaft and matching gear, and one dot each for
the auxiliary shaft remaining gear, see Fig. 9b.
3. Fit the drive shaft gear onto the drive shaft making sure the identity marks lie on the
same plane. Fit circlip.
4. Locate the remaining gear onto the auxiliary shaft, carefully engaging the teeth with
the drive shaft gear. The dot mark on the auxiliary gear tooth must be positioned
between the two dot marks on the drive shaft gear, see Fig. 9c. If new gears are
being fitted:
4.1 Load one gear onto the drive shaft spline. Fit circlip.
4.2 Locate the remaining gear onto the auxiliary shaft spline and engage the teeth into
the drive shaft gear.
4.3 Check the clearances of the rotors with feeler gauges at the measurement positions
shown in Fig. 9a. If the clearances are approximately equal either side, turn the
drive shaft to ensure there is no interference between the rotors.
4.4 If clearances are correct, proceed to step 5.
4.5 If the clearances are incorrect, the auxiliary gear will have to be removed, rotated by
3 teeth, and replaced.
4.6 To move the gears, mark (with a suitable pen) the tooth of the auxiliary shaft gear
which fully engages with the drive shaft gear teeth.
4.7 Repeat the above until the correct clearances are obtained. The gears and shafts
should be dot punched as detailed in procedure step 2, to avoid repetition of the
above in future maintenance of the pump.
5. Now that the rotors have been correctly timed, the remaining circlip should be care
fully relocated in the shaft recess using circlip pliers. If the pump is fitted with
hydraulic drive, the drive adaptor should now be replaced.
Page 16
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