General Pump MK Repair Manual

MMKK

Repair Manual

MK55A-MK60A-MK65A

MK40A-MK45A-MK50A

GENERAL PUMP

INDEX

1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 3

2. REPAIR INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 3

2.1 Crank Mechanism Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 3

2.1.1 Crank Mechanism Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 4

2.1.2 Crank Mechanism Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 13

2.1.3 Refurbishing the Crank Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . .Page 23

2.2 Fluid End Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 24

2.2.1 Head Disassembly - Valve Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 24

2.2.2 Head Assembly - Valve Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 27

2.2.3 Disassembling the Plunger Unit - Supports - Seals . . . . . . . . . . . . . .Page 33

2.2.4 Assembly of the Plunger Unit - Suports - Seals . . . . . . . . . . . . . . . . .Page 36

2.2.5 Manifold Refurbishment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 41

3. SCREW CALIBRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 43

4. REPAIR TOOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 44

5. MAINTENANCE LOG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 45

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MK SERIES

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GENERAL PUMP

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MK SERIES

1. INTRODUCTION

This manual describes the instructions for Repairing MK Series pumps, and must be carefully read and
understood before performing any repair intervention on the pump. Correct use and adequate maintenance is
fundamental for the pump’s regular operation and long wear. General Pump declines any responsibility for
damage caused by the misuse or the non-observance of the instructions described in this manual.

2. REPAIR INSTRUCTIONS

2.1 Crank Mechanism Repair

Crank mechanism repair operations must be carried out after draining the oil from the crankcase. To drain
the oil, remove the oil refill cap 1, Fig. 1, and then the draining plug (2, fig. 1).

Exhausted oil must be collected in an appropriate receptacle and disposed of in
designated locations. In absolutely no case may it be disposed of in the environment.

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GENERAL PUMP

2.1.1 Crank Mechanism Disassembly

The correct sequence is the following

Completely drain the oil from the pump, then remove the key from the shaft (1, fig.2).

Unscrew the reducer flange fastening screws (1, fig. 3) and remove the flange from the shaft.

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MK SERIES

On the opposite side, unfasten the screws (1, fig. 4) and therefore remove the bearing cover.

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GENERAL PUMP

Disassemble the crankcase cover by unfastening the relevant screws (1, fig. 5).

Unfasten the reducer cover screws (1, fig. 6).

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MK SERIES

Insert 3 dowels, or 3 M8 threaded screws (1, fig. 7) in the appropriate holes to aid extraction, and two
sufficiently long M10 screws in order to support the cover (2, fig. 7).

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GENERAL PUMP

Screw on the 3 threaded screws (1, fig. 8) and simultaneously, using the appropriate tool (p/n 27516700),
hammer on the tool itself so that the bearing remains on the pinion when extracting the cover (1, fig. 9).

When this operation is complete, remove the reducer cover and then slip off the bearing from the pinion.
Remove the screws that fasten the ring gear stopper (1, fig. 10), and remove the stopper itself (1, fig. 11).

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MK SERIES

Remove the ring gear (1, fig. 12). If necessary, use a slide hammer applying it to the 2 M8 holes (2, fig. 12).

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GENERAL PUMP

Remove the key from the shaft (1, fig. 13).

Remove the pinion by using a slide hammer applying it to the M14 hole (1, fig. 14).

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MK SERIES

Lift the safety washer key (1, fig. 15)

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GENERAL PUMP

Insert a spacer under the connecting rod to block shaft rotation (1, fig. 16).

Using an appropriate wrench, unscrew and remove the ring nut (1, fig. 17) and then remove the safety
washer (1, fig 18).

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MK SERIES

Screw a SKF KM19 type ring nut onto the pressure sleeve (1, fig. 19), then loosen the sleeve using an
appropriate wrench (1, fig. 20).

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GENERAL PUMP

On the opposite side, unfasten the reducer case screws (1, fig. 21), and then remove the case (1, fig. 22).

Unscrew the connecting rod screws (1, fig. 23).

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MK SERIES

Disassemble the connecting rod caps with the split bearings; be particularly aware of disassembly order.

The connecting rod caps and the related connecting rods must be reassembled in the

exact order and coupling as during disassembly.

To avoid error, caps and connecting rods are numbered on one side (1, fig. 24).

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GENERAL PUMP

Push the connecting rods forward in the direction of the hydraulic side in order to push out the crankshaft.
Use the appropriate tool (p/n 27566200) to facilitate this operation (1, fig. 25)

Remove the pressure sleeve (1, fig. 26).

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MK SERIES

Remove the upper split bearing of the connecting rods (1, fig. 27).

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GENERAL PUMP

Remove the crankshaft with the help of a hammer on the PTO side (1, fig. 28). Remove the shaft and the
bearing (1, fig. 29).

On the opposite side, extract the bearing (1, fig. 30)

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MK SERIES

If the replacement of one or more connecting rods or plunger guides is necessary, please operate as follows:
Unfasten the screws of the tool (p/n 27566200 to unlock the connecting rods (1, fig. 31) and therefore
extract the connecting rod-plunger guide units from the opening behind the crankcase (1, fig. 32).

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GENERAL PUMP

Couple the connecting rods with the previously disassembled caps; be sure to respect numbering (1, fig. 33).

Remove the two seeger rings that block the plunger pin by using the appropriate tool (1, fig. 34).

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MK SERIES

Remove the pin (1, fig. 35) and then remove the connecting rod (1, fig. 36).

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GENERAL PUMP

To separate the rod from the plunger guide, unfasten the M10 hexagonal-head screws using a size 17 socket
wrench (1, fig. 37).

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MK SERIES

2.1.2 Crank Mechanism Assembly

Proceed with assembly by inverting the precedure indicated in paragraph 2.1.1.
The correct sequence is the following:

Connect the rod to the plunger guide
Insert the Ø5 pin in the appropriate hole on the plunger guide (1, fig. 38) and connect the rod to the plunger
guide using M10 x 35 screws (1, fig. 39).

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GENERAL PUMP

Block the rod using a clamp, and proceed with calibration using a torque wrench (1, fig. 40) as indicated
in paragraph 3. “SCREW CALIBRATION”

Insert the connecting rod in the plunger guide (1, fig. 36) and then insert the pin (1, fig. 35). Apply the
two seeger rings using the correct tool (1, fig. 34).

Make sure that conrods, plunger guides and wrist pins can move freely after being
assembled.

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MK SERIES

Separate the caps from the connecting rod; correct coupling is guaranteed by the numbering on the side
(1, fig. 33).

After verifying the perfect cleaning of the crankcase, insert the connecting rod-plunger guide unit inside the
cylinders of the crankcase (1, fig. 32).

The insertion of the connecting rod-plunger guide unit inside crankcase must be done
by positioning the connecting rods with the numbering visible from above.

Block the three units using the correct tool, p/n 27566200(1, fig 31).

Pre-assemble the bearing, PTO side, on the shaft (1, fig. 41) and assemble the bearing on the opposite
side on the crankcase (1, fig. 42).

The bearing in fig. 42 has a tapered internal ring. Verify that the taper goes from the
outside towards the inside in order to allow the subsequent insertion of the sleeve.

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