Dolmar PS-6400 Operating instructions

1Repair Manual PS-6400/PS-7300/PS-7900
02/05
Repair Manual
www.dolmar.com
PS-6400, PS-6400 H
PS-7300, PS-7300 H
PS-7900, PS-7900 H

2Repair Manual PS-6400/PS-7300/PS-7900
Technical data ......................................................................................... 3
Troubleshooting ...................................................................................... 4
00 Special tools ....................................................................................... 5 - 6
01 Sprocket guard / Chain tensioning system .......................................... 7
02 Clutch drum / Rim sprocket ................................................................... 8
03 Chain brake ....................................................................................... 9 - 14
04 Clutch .............................................................................................. 15 - 16
05 Oil pump .......................................................................................... 17 - 19
06 Starter .............................................................................................. 20 - 22
07 Ignition system ............................................................................... 23 - 26
08 Carburetor ....................................................................................... 27 - 31
09 Vibration damper / Tubular handle .............................................. 32 - 33
10 Tank ................................................................................................. 34 - 35
11 Cylinder / Piston .................................................................................... 36
12 Outside components / Crankcase / Crankshaft........................... 37 - 38
13 Handle Heating ................................................................................. 39-41
14 Torques .................................................................................................. 42
15 Check operation .................................................................................... 43
CONTENTS

3Repair Manual PS-6400/PS-7300/PS-7900
TECHNICAL DATA
Stroke volume cm364,2 72.6 78.5
Bore mm 47 50 52
Stroke mm 37 37 37
Max. power at speed 3) kW / 1/min 3.5 / 9,000 4.2 / 9,500 4.6 / 9,500
Max. torque at speed 3) Nm / 1/min 4.2 / 6,500 4.8 / 7,000 5.2 / 7,000
Idling speed / max. engine speed with bar and chain 1/min 2,500 / 13,500 2,500 / 13,500 2,500 / 13,500
Clutch engagement speed 1/min 3,200 3,200 3,200
Sound pressure level at the workplace LpA av per ISO/CD 22868 1) dB (A) 104.3 104.3 104.3
Sound power level LWA av per ISO/CD 22868 1) dB (A) 113.3 113.3 113.3
Vibration acceleration ah,w av per ISO 7505 1)
- Tubular handle m/s26.9 6.9 6.9
- Rear handle m/s27.7 7.7 7.7
Carburetor (diaphragm carburetor) Type ZAMA
Ignition system Type electronic
Spark plug Type NGK BPMR 7A
Electrode gap mm 0.5
or spark plug Type BOSCH WSR 6F
Fuel consumption at max. load per ISO 7293 3) kg/h 1.72 2.33 2.3
Specific consumption at max. load per ISO 7293 3) g/kWh 500 510 505
Fuel tank capacity l 0.75
Chain oil tank capacity I 0.42
Mixture ratio (fuel/two-stroke oil)
- when using DOLMAR oil 50 : 1
- when using other oils 40 : 1
Chain brake engages manually or in case of kickback
Chain speed 2) m/s 19.74 20.83 20.83
Sprocket pitch inch 3/8
Number of teeth Z 7
Chain type see the Extract from the spare-parts list 099
Pitch / gauge inch 3/8 / .058
Guide bar, length of a cut cm 38 / 45 / 50 / 60 / 70
Guide-bar type see the Extract from the spare-parts list
Weight (fuel tank empty, without chain and guide bar) kg 6.3 6.3 6.3
1) Figures derived in equal part from idling, full-load and racing speed.
2) At max. power
3) For models without starting valve
Technical data PS-6400 PS-7300 PS-7900

4Repair Manual PS-6400/PS-7300/PS-7900
TROUBLESHOOTING
Malfunction System Observation Cause
Chain does not run Chain brake Engine runs Chain brake actuated.
Engine does not start or Ignition system Ignition spark Malfunction in fuel supply system, com-
only with difficulty pression system, mechanical malfunction.
No ignition spark Switch on STOP, fault or short-circuit in the
wiring, plug cap or spark plug defective.
Fuel supply Fuel tank is filled Choke in wrong position, carburetor defective,
fuel filter dirty, fuel line bent or interrupted, torn,
perforated
Compression Inside Cylinder base packing ring defective, radial
system shaft packings defective, cylinder or piston rings
defective
Outside Spark plug does not seal.
Mechanical Starter does not engage Spring in starter broken, broken parts
malfunction inside the engine.
Warm engine doesn‘t Carburetor Fuel tank is filled Wrong carburetor adjustment,
start Ignition spark flooded by usage of the ckoke
Engine starts, but Fuel supply Fuel tank is filled Wrong idling adjustment, fuel filter or
dies immediately carburetor dirty. Tank venting defective, fuel
line interrupted, cable defective, STOP switch
defective. Decompression valve dirty
Insufficient power Several systems Engine is idling Air filter dirty, wrong carburetor adjustment,
may be involved muffler clogged, exhaust channel in cylinder
simultaneously clogged, spark arrester screen clogged, worn piston
No chain lubrication Oil tank/pump No oil on the chain Oil tank empty, oil guide groove dirty,
oil-pump adjusting screw incorrectly adjusted,
oil pump drive defective

5Repair Manual PS-6400/PS-7300/PS-7900
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4
5
6
00 SPECIAL TOOLS
1 Torx screwdriver
Grip (944.500.860)
T-grip, 200 mm (944.500.862)
T-grip, 100 mm (944.500.861)
2 Radial ring puller
15 mm radial ring puller (944.xxx.xxx)
17 mm radial ring puller (944.xxx.xxx)
Spindle (950.203.020)
3 Mandrel
Disassembly mandrel for
knocking the flywheel
loose without damage to
the crankshaft thread (944.500.880)
4 Setting gauge
Gauge for measuring the gap
between flywheel and
ignition armature (944.500.891)
5 Torque wrench
3/8” Drive socket (944.500.864)
Bit, 152 mm (944.500.865)
Bit, 49 mm (944.500.866)
Torque wrench
3/8” Drive (950.230.000)
6 Piston stop wedge
Wedge for blocking the motor
through the exhaust port (944.602.000)

6Repair Manual PS-6400/PS-7300/PS-7900
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10 11
9
00 SPECIAL TOOLS
7 Piston ring tensioner
Piston ring band and
assembly tool for cylinders (944.600.001)
8 Assembly and disassembly wrench
Wrench for disassembling and assembling
the centrifugal clutch (944.500.570)
9 Pressure gauge
Pressure guage for checking
the carburetor fuel valve (956.004.000)
10 Tachometer
Electronic tachometer for measuring
the engine speed of
2- and 4-stroke engines (950.233.210)
11 Installation sleeve
for radial rings (944.603.410)

7Repair Manual PS-6400/PS-7300/PS-7900
01 SPROCKET GUARD / CHAIN TENSIONING SYSTEM
How the chain tensioner works
The force applied to the adjusting screw is transferred
by the angle worm drive to the tensioning pin.
Replace the chain guide 1if it is worn.
Mount the housing 2in the sprocket guard with
slotted screw 3(3.5 x 9.5).
NOTE: The worm drive is available only as a set 5.
Grease the spindle and worm with multipurpose
grease (944.360.000).
Chip guide
The chip guide ensures that chips are deflected away
from the cut.
This is especially important for rip cuts, to prevent
clogging.
To replace it, push the catch 4inwards from the
outside of the chain guard.
Tool
1
2
5
3
(1,5 Nm ± 0,2)
4
(1.5 Nm ± 0.2)

8Repair Manual PS-6400/PS-7300/PS-7900
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7
Sprocket, clutch drum and needle
bearing
Inspect the sprocket for damage and wear.
Important customer information:
Before installing a new chain the sprocket must be
inspected.
Worn sprockets will damage a new saw chain and
must always be replaced.
Check the clutch drum bearing for damage and wear.
Assemble with multipurpose high-performance
grease (944.360.000).
Check the clutch drum for damage and wear, and
replace if worn.
Note:
Always use a new circlip (927.408.000)!
02 CLUTCH DRUM / RIM SPROCKET

9Repair Manual PS-6400/PS-7300/PS-7900
12
03 CHAIN BRAKE
Chain brake
The chain brake stops the chain within 0.1 seconds
in the event of kickback.
The brake band 2encircles the clutch drum 380°.
A spring 1pulls the brake band around the clutch
drum.

10Repair Manual PS-6400/PS-7300/PS-7900
03 CHAIN BRAKE
Engage the chain brake
Push the hand guard forward so that the linkage
release the spring tension.
Safety note:
Strong spring!
Never work on the chain brake when the spring
is under tension!

11Repair Manual PS-6400/PS-7300/PS-7900
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1
5
3
4
6
89
2
(1,5 Nm ±0,2)
7 (1,5 Nm ±0,2)
03 CHAIN BRAKE
Removing the sprocket and clutch drum,
exposing the chain brake
Remove the sprocket guard, saw chain and guide
bar.
Remove the chain guide plate 1, assembly with
slotted screw 2(3.5 x 9.5 mm).
Remove the washer 3and pull off the sprocket 4
with discs.
Pull the hand guard slightly towards the tubular
handle (do not let it disengage!) and hold it firmly,
to cancel the brake force on the clutch drum.
Important: If the hand guard disengages, push
it forward again.
Never actuate the hand guard without the
clutch drum! This could break the linkage or the
housing.
Remove the clutch drum 5(note needle bearing 6)
and release the hand guard again slowly.
Remove the covering plate 8, assembly with slot
head screw 7(3.5 x 9.5 mm).
Remove foam sponge 9.
Tool

12Repair Manual PS-6400/PS-7300/PS-7900
1
3
(1,5 Nm ± 0,2)
2
Replacing the brake band
Loosen screw 2.
Lever brake band 1out of the housing and turn it
90° to disengage it from the lug 3.
Check the inside of the brake band for signs of wear.
The chain brake is an important safety
component. Always check it for wear.
A worn brake band must be replaced
(927.408.000)!
Tool
03 CHAIN BRAKE

13Repair Manual PS-6400/PS-7300/PS-7900
1
2
3
4
5
Removing the brake spring
Disassembly
Secure the engine unit against slipping.
Disassamble the muffler.
Remove circlip 1.
Using the universal wrench as shown in the picture
and push against the spring pressure, while twisting
it back and forth slightly and pulling up. This will
lever the linkage from the pin.
Pull the disengagement mechanism 2out of the
spring 3.
Pull the spring 3out of the spring housing 4and
pull the spring housing out of the housing.
Assembly
Before assembly, drive the slotted pin 5out of the
housing with a mandrel (dia. 4 mm) in the direction
of the muffler.
Install the disengagement mechanism and insert
the grooved pin.
Important: The circlip 1 must be inserted in the
bottom groove.
Tool
03 CHAIN BRAKE

14Repair Manual PS-6400/PS-7300/PS-7900
1
(4,0 Nm + 0,5)
2
(4,0 Nm + 0,5) 3
45
Removing the hand guard
Engage the chain brake.
Unscrew Torx screw 1(M5 x 20).
Remove bushing 2.
Unscrew Torx screw 3(908.005.206, M5 x 25,
microencapsulated). When reassembling, always
replace screw 3or secure it with “Loctite 243”
(980.009.000).
Remove bushing 4.
Push linkage arm 5up slightly and disengage (it
may be necessary to hold the pin against it).
Remove hand guard.
Tool
03 CHAIN BRAKE
(4.0 Nm + 0.5)
(4.0 Nm + 0.5)

15Repair Manual PS-6400/PS-7300/PS-7900
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04 CLUTCH
Clutch
The clutch has 3 centrifugal weights. At speeds over
3200 rpm it engages the clutch drum.
The weights are held on the clutch hub with 3 tension
springs.
The maximum idle is 2600 rpm.
If the clutch drum engages (i.e. the chain turns) under
3200 rpm, clean and inspect the clutch. It may be
necessary to replace the springs.
Remove the muffler.
Block the engine with piston stop wedge
(944.602.000).
Remove the clutch drum (see page 11).
Loosen the clutch 1with assembly tool (944.500.570)
by turning clockwise.
Tool

16Repair Manual PS-6400/PS-7300/PS-7900
(55,0 Nm ± 2,5)
(10,0 Nm + 1,0)
1
2
3
4
04 CLUTCH
Replacing the springs
If the chain moves at engine speeds below 3200 rpm,
replace the springs (024.184.021).
Remove and replace the springs with needle-nose
pliers.
Insert the centrifugal weights with the “TOP” lettering
towards the outside.
Careful!The springs can fly out and cause injury.
Assembly note: Disassemble the starter assy to
prevent a damage of the starter ratchets.
Push the disc washer 1into the clutch.
Use the assembly wrench (944.500.570) to tighten
the clutch.
The lug 3of the clutch drum should not be on the
arms of the oil pump drive 2.
Replace the muffler gasket 4(965.531.130).
Tool
(10.0 Nm + 1.0)
(55.0 Nm ± 2.5)

17Repair Manual PS-6400/PS-7300/PS-7900
4 (8,0 Nm + 1,0)
2
1
3
05 OIL PUMP
General
The oil pump is driven by the clutch drum.
Lugs 1on the clutch drum transfer power to the arms
on the oil pump drive 2. The drive worm of the oil
pump drive engages in the teeth of the oil pump
piston 3.
This means that oil is supplied only when the saw
chain is moving.
The oil pump is attached to the crankcase with 2
Torx screws 4M5 x 12.
Removing the clutch drum, see page 11.
Removing the clutch, see page 15.
Tool
(8.0 Nm + 1.0)

18Repair Manual PS-6400/PS-7300/PS-7900
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3
1
05 OIL PUMP
Oil tank
The oil tank 1holds 0.42 liter and is formed by the
halves of the crankcase.
The large oil tank cap 3makes oil filling easy.
The oil tank is ventliated by valve 2in the crankcase.
To replace it, drive the valve into the tank with a
mandrel (dia. 4 mm) and press in a new valve from
the outside with a mandrel (dia. 8 mm).
CAUTION: Use mandrel with planar surface!

19Repair Manual PS-6400/PS-7300/PS-7900
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7
2
34
5
6
05 OIL PUMP
Oil lines
The oil screen 1must be cleaned periodically.
The oil suction line 2connects the oil tank and oil
pump.
When inserting the suction line into the hole in the
crankcase coat the collar with silicone paste
(980.007.100).
Note the position of the lug 3!
Then insert the angle nipple 4and oil hose 5.
The oil pressure line 6links the oil pump and the
guide bar connection.
Adjusting the supply rate
CAUTION: The adjustment range is smaller than
1/4 turn (70°)!
The oil supply rate is regulated with the adjusting
screw 7.The adjusting screw is on the bottom of the
housing.
The oil pump is factory adjusted to a medium supply
rate.
To change the setting, use a screwdriver (max. 5
mm tip) to turn the adjusting screw:
• Right for reduced oil supply
• Left for more oil supply
Even very small turns of adjusting screw 7influence
the amount of oil supplied to the bar and chain.
Adjustment range 70°

20Repair Manual PS-6400/PS-7300/PS-7900
1 (4,0 Nm + 1,0)
4,5 Nm ± 1,0
2
06 STARTER
Starter
The fan housing is bolted onto the crankcase with 3
Torx/slotted screws 1(M5x20).
Induction channel
The air duct 2guides the inducted cool air to the
cylinder for proper operation.
Tool
(4.0 Nm + 1.0)
4.5 Nm ± 1.0