Husqvarna 331RB Workshop Manual Download

Page: 22 / 48

7.6.7 To clean and examine the carburetor

1. Examine the wear to the lever arm and the wear of

the needle valve. Replace damaged parts.

2. Examine the other parts of the carburetor. Replace

damaged parts.

7.6.8 To adjust fuel flow to the carburetor

1. Disassemble the carburetor, refer to

To disassemble

and assemble the carburetor on page 20.

2. To adjust the fuel flow for idle speed or middle

speed: Move the clip of the jet needle to the correct

position.

a) Move the clip to the top groove (A) for low fuel

flow.

b) Move the clip to the middle groove (B) for

standard fuel flow.

c) Move the clip to the bottom groove (C) for high

fuel flow.

3. To adjust the fuel flow for high speed: Replace the

main nozzle.
a) Use a smaller main nozzle to increase the fuel

flow.

b) Use a larger main nozzle to decrease the fuel

flow.

7.6.9 To adjust the idle speed

The idle speed is adjusted at the factory before the

product is supplied. An adjustment of the idle speed can

become necessary because of changes in the operation

conditions, for example, in the air.

WARNING: If the cutting attachment does not

stop when you adjust the idle speed, speak to

your servicing dealer. Do not use the product

until it is correctly adjusted or repaired.

•

Make sure that the throttle wire is parallel with the

flexible shaft. If the throttle wire is twisted, make the

throttle wire straight.

•

If the shaft is bent, the play of the wire is changed.

Make the shaft straight and put the product in the

position you usually operate it before you adjust the

idle speed.

•

The idle speed is correct when the engine operates

smoothly in all positions. The correct idle speed is

set when the product does not stop and the cutting

equipment does not rotate.

1. Start the engine and operate the product at half

speed for >2 minutes until the engine becomes

warm.

2. Turn the idle adjustment screw clockwise until the

cutting attachment starts to rotate.

3. Turn the idle adjustment screw counterclockwise

until the cutting attachment stops.

Note: Refer to

Technical data on page 46 for the

recommended idle speed.

22 - Repair instructions

1281 - 001 -

Summary of Contents for 331RB

Page 1: ...Workshop manual 331RB English 1281 001 ...

Page 2: ...cing tools 8 6 Function overview 6 1 Type plate Product serial number 10 6 2 Fuel 10 7 Repair instructions 7 1 Product overview for repair instructions 11 7 2 To clean and examine the product parts 12 7 3 Starter 12 7 4 Muffler 15 7 5 Air filter 15 7 6 Carburetor 16 7 7 Ignition system 23 7 8 Centrifugal clutch 28 7 9 Cylinder and piston 29 7 10 Crankshaft and crankcase 33 7 11 Harness frame 37 7 ...

Page 3: ...nderstand the manual 1 3 Revisions Changes to the product can cause changes to the maintenance work and spare parts Separate information is sent out for each change Read the manual together with all received information about changes to maintenance and spare parts for the product 1 4 Safety WARNING All personnel that repair or do servicing on the product must read and understand the safety instruc...

Page 4: ...he product can result in permanent hearing loss 2 4 Symbols on the product WARNING This product is dangerous Injury or death can occur to the operator or bystanders if the product is not used carefully and correctly To prevent injury to the operator or bystanders read and obey all safety instructions in the operator s manual Please read the operator s manual carefully and make sure that you unders...

Page 5: ...e is sharp and not damaged Make sure the blade is installed correctly in the center position Examine the trimmer head Make sure that the idle speed functions correctly Examine the locknut Do a check of fuel leaks Examine the transport guard Examine the starter rope handle and the starter rope Make sure that the bevel gear grease is sufficient Clean the external part and the adjacent areas of the c...

Page 6: ... mm 3 4 Nm 4 mm 2 3 Nm 8 mm 3 5 Nm 10 mm 7 9 Nm 10 mm 7 9 Nm 4 mm 3 5 Nm 4 mm 3 5 Nm 4 mm 4 6 Nm 4 mm 4 6 Nm 19 mm 18 20 Nm 13 mm 18 20 Nm 13 mm 18 20 Nm 17 mm 18 20 Nm 4 mm 6 8 Nm 5 mm 8 10 Nm 5 mm 6 8 Nm 4 mm 6 8 Nm 4 mm 6 8 Nm 4 mm 6 8 Nm 3 mm 2 3 Nm 6 Servicing data 1281 001 ...

Page 7: ...0 8 1 5 Nm 5 mm 4 6 Nm 0 6 1 Nm 1 5 2 5 Nm 0 6 1 Nm 4 mm 1 5 2 5 Nm 4 mm 3 5 Nm 19 mm 18 20 Nm 5 mm 3 5 Nm 5 mm 6 8 Nm 1 2 2 Nm 1 2 2 Nm 2 5 3 5 Nm 1 2 2 Nm 1281 001 Servicing data 7 ...

Page 8: ...5 Servicing tools 5 1 Servicing tools 11 9 3 12 13 14 10 1 2 4 5 6 7 8 15 16 8 Servicing tools 1281 001 ...

Page 9: ...move the fuel filter 502 50 83 01 10 Pin Lock the angle gear 502 02 61 02 11 Carburetor adjustment screwdriver Adjust the carburetor settings 501 60 02 03 12 Tachometer Measure the engine rpm 502 71 14 01 13 Grease Lubricate the parts in the angle gear 503 97 64 01 14 Hex key 4 mm 502 50 18 01 14 Hex key 5 mm 502 50 64 01 15 Air gap tool 0 3 mm Adjustment of the ignition module 502 51 34 02 16 Dri...

Page 10: ...ct the correct oil CAUTION Do not use two stroke oil for water cooled outboard engines also referred to as outboard oil Do not use oil for four stroke engines 6 2 4 To mix gasoline and two stroke oil Gasoline l Two stroke oil l 2 50 1 5 0 10 10 0 20 15 0 30 20 0 40 CAUTION Small errors can change the ratio of the mixture when you mix small quantities of fuel Measure the quantity of oil carefully a...

Page 11: ...Product overview for repair instructions 5 3 4 7 9 1 2 6 8 12 13 14 10 11 1 Starter 2 Muffler 3 Air filter and air filter holder 4 Carburetor 5 Clutch drum cover and clutch drum 6 Ignition module 1281 001 Repair instructions 11 ...

Page 12: ...crews and pull out the starter and the gasket 2 Pull out the starter rope approximately 30 cm 3 Put your thumb on the starter pulley 4 Put the starter rope in the groove in the starter pulley 5 Let the starter pulley rotate rearward until the spring tension stops WARNING Be careful the recoil spring can cause injury to your thumb when the starter pulley rotates rearward 6 Remove the screw A the wa...

Page 13: ...ble and enters the groove on the starter pulley 3 Wind the cord 3 turns counterclockwise around the starter pulley 4 Lubricate the recoil spring and the stub axle of the starter pulley with cold resistant grease or thin oil 5 Put the starter rope through the opening in the starter housing and the opening in the bearing journal 7 3 4 To assemble the starter 1 Put the torsion spring in the pulley an...

Page 14: ... 4 screws 7 Tilt the starter slightly forward to make sure that the starter is installed correctly on the cylinder cover and on the muffler 7 3 5 To replace the starter pawl assembly 1 Remove the starter Refer to To disassemble the starter on page 12 2 Remove the spark plug cap and the spark plug 3 Put a piston stop in the spark plug hole to lock the axle 4 Loosen the nut Remove the starter pawl a...

Page 15: ...orrectly attached to the product 7 5 Air filter 7 5 1 To remove and install the air filter 1 Turn the engine around its axle to get access to the air filter 2 Turn the knob A to remove the air filter cover B A B E F C D 3 Remove the air filter C 4 Remove the 2 screws D the air filter net E and the air filter holder F 5 Install the air filter in the opposite sequence 7 5 2 To clean and examine the ...

Page 16: ...at to the needle valve The carburetor float is in the float chamber The carburetor float is connected to the needle valve with the lever arm The carburetor float moves up if the fuel level in the float chamber is high The carburetor float moves down if the fuel level in the float chamber is low When the fuel level decreases the carburetor float moves down and opens the needle valve When the needle...

Page 17: ...ion 7 6 3 2 Part throttle position 7 6 3 3 High speed position 7 6 4 Gravity fuel supply The fuel tank is installed above the carburetor Gravity causes the fuel to go from the fuel tank to the carburetor The fuel valve B is installed between the fuel tank and the carburetor and stops the fuel The gravity fuel supply limits the product from tilted 1281 001 Repair instructions 17 ...

Page 18: ...operation If the product is tilted too much the fuel does not go into the carburetor B 18 Repair instructions 1281 001 ...

Page 19: ...26 17 22 6 19 1 Top cap 2 Piston valve 3 Needle valve 4 Idle adjustment screw 5 Choke plate 6 Washer 7 Nut 8 Gasket 9 Hose 10 Screw 11 Fuel drain screw 12 Float chamber housing 13 Carburetor float 14 Fuel jet 15 Lever arm 16 Axle 17 Needle valve 18 Choke lever 1281 001 Repair instructions 19 ...

Page 20: ...ntenance on the engine the fuel valve must be closed 1 Disconnect the throttle wire 2 Turn the engine to get access to the air filter assembly Remove the air filter assembly A B C D E and F A B E F C D 3 Disconnect the fuel hose from the carburetor 4 Remove the 2 screws G the carburetor H the washer I the distance piece J and the washer K G I J H K 20 Repair instructions 1281 001 ...

Page 21: ...he lever arm V the axle X and the needle valve Y Y V X U 8 Remove the idle adjustment screw Z AD AB AA AH AI AE AF AG AJ AK AC Z 9 Remove the nut AA the washer AB the choke lever AC and the choke plate AD 10 Remove the 2 screws AE the adapter AF and the sealing AG 11 Remove the 2 screws AH and the washers AI 12 Remove the fuel valve AJ and the washer AK 13 Assemble the carburetor in the opposite s...

Page 22: ...speed can become necessary because of changes in the operation conditions for example in the air WARNING If the cutting attachment does not stop when you adjust the idle speed speak to your servicing dealer Do not use the product until it is correctly adjusted or repaired Make sure that the throttle wire is parallel with the flexible shaft If the throttle wire is twisted make the throttle wire str...

Page 23: ...ark plug is dirty clean it and make sure that the electrode gap is correct refer to Technical data on page 46 Replace the spark plug if it is necessary 7 7 3 To do a spark test of the ignition module 1 Disconnect the spark plug cable from the spark plug 2 Disconnect the spark plug from the cylinder 3 Connect the ignition tester to the spark plug cap and ground the clip to the cylinder 4 Use the kn...

Page 24: ...pliers to make the new hole 6 Put the spring into the new hole 7 Put the cable with the open spring into the other slot in the pliers Close the pliers to bend the spring CAUTION Make sure that the spring is bent 90 degrees along the cable 8 Lubricate the cap with soap and water or equivalent to make it easier to push it into position 9 Push the cable into the spark plug cap 24 Repair instructions ...

Page 25: ...ed spark plug cap can cause an electrical shock 7 7 5 To disassemble the ignition system 1 Pull up the knob and remove the shaft 2 Remove the spark plug cap 3 Remove the spark plug 4 Put a piston stop in the spark plug hole to prevent movement of the piston 5 Disconnect the throttle wire from the carburetor 6 Disconnect the cables 1281 001 Repair instructions 25 ...

Page 26: ...ve the 5 screws and the flywheel cover 11 Remove the screws the washers the cables and the ignition module 12 Remove the 2 screws and the 2 washers that hold the centrifugal clutch Remove the centrifugal clutch and the 2 washers between the flywheel and the centrifugal clutch 13 Attach the flywheel puller apart from the center unit on the flywheel 26 Repair instructions 1281 001 ...

Page 27: ...ot on the thread 2 Make sure that the keyway in the flywheel and the keyway in the crankshaft are not damaged Make sure that the key is not damaged 3 Attach the flywheel and the centrifugal clutch with the spacers and screws as shown in the illustration Note Turn the clutch until you can see the arrows that show the direction of rotation 4 Assemble the cables to the ignition module Use the 2 screw...

Page 28: ...site sequence as the were removed Refer to To disassemble the ignition system on page 25 7 8 Centrifugal clutch 7 8 1 To remove the centrifugal clutch 1 Pull up the knob and remove the shaft 2 Remove the 4 screws Remove the clutch drum assembly 3 Put a piston stop in the spark plug hole to prevent movement of the piston 28 Repair instructions 1281 001 ...

Page 29: ...ace damaged parts 3 Clean all parts 7 8 3 To examine the clutch drum 1 Examine the clutch drum for wear Replace the clutch drum if it is worn or damaged 2 Measure the diameter of the clutch drum Replace the clutch drum if the diameter is more than mm 7 8 4 To install the centrifugal clutch 1 Put some grease on the clutch screw but not on the thread 2 Install the centrifugal clutch in the opposite ...

Page 30: ... access to the cylinder and piston 2 Loosen the 4 bolts and pull the cylinder up 3 Remove the cylinder base gasket 4 Put a cloth on top of the crankcase opening to make sure that no dirt goes into the crankcase 5 Use a pointed tool to remove the G snap rings for the wrist pin 6 Push the wrist pin from the piston with a punch of the correct dimension 7 Remove the piston and the needle bearing from ...

Page 31: ...inder is not worn especially in the top end of the cylinder Make sure that the cylinder does not have score marks 7 9 5 To examine the piston Make sure that the piston ring can move freely in the groove Examine the surface of the piston for damage and wear Examine the piston pin Refer to To examine the piston pin on page 32 Examine the snap rings If the snap rings have cracks or discoloration repl...

Page 32: ...rations or damages 7 9 6 To assemble the cylinder and piston 1 Carefully put the piston ring on the piston Make sure that you do not cause damage to the piston ring or the piston 2 Lubricate the needle bearing with two stroke oil and put it into the connecting rod Make sure the needle bearing moves freely in the connecting rod 3 Attach the piston to the connecting rod Point the arrow at the piston...

Page 33: ...ase 7 10 1 To disassemble the crankshaft and crankcase To get access to the crankshaft and crankcase you must remove all components of the product Refer to the manual section for each component for instructions 1 Remove the starter Refer to To disassemble the starter on page 12 2 Remove the ignition system Refer to To disassemble the ignition system on page 25 3 Remove the muffler Refer to To remo...

Page 34: ... be replaced if it is worn or damaged 1 Examine the large end of the connecting rod Replace the crankshaft if you see scratch marks discoloration on the sides or damaged needle holders 2 Examine the small end of the connecting rod Replace the crankshaft if you see scratch marks or discoloration in the bearing track 3 Examine the bearing Make sure the connecting rod does not have radial play Make s...

Page 35: ... The sealing ring on the flywheel side must be 0 5 1 mm below the edge of the bearing seat Make sure that the sealing ring levels with the crankcase on the starter side 3 Attach the crankshaft a Lubricate the stub axle of the crankshaft and the large end of the connecting rod with some drops of two stroke oil Do not put oil on the threads b Carefully move the crankshaft C into the bearing in the c...

Page 36: ...ngs of the wrist pin in the slots c Put the flywheel key in the crankcase keyway with the flat surface parallel to the center line of the crankshaft d Attach the flywheel 7 Attach and lubricate the cylinder a Put the cylinder base gasket G in the correct position b Put the plate from the piston assembly kit H below the piston to make sure that the piston is stable c Lubricate the piston and piston...

Page 37: ... the harness frame 1 Drain the fuel tank 2 Pull up the knob and remove the shaft 3 Disconnect the throttle wire and the cables from the carburetor 4 Disconnect the fuel hose from the carburetor 5 Remove the nut A and the washers B and C B A C 6 Remove the engine from the support plate on the harness frame 1281 001 Repair instructions 37 ...

Page 38: ...fuel tank from the frame 7 12 Handle and throttle trigger 7 12 1 To disassemble the handle 1 Remove the 7 screws and 2 nuts 2 Remove the handles halves from the rod 3 Remove the throttle trigger A and the spring B Remove the spring C Remove the throttle lock D C A B D 4 Remove the throttle wire E from the throttle trigger A E A 38 Repair instructions 1281 001 ...

Page 39: ...1 Assemble the black cable G and red cable F in the cable retainer K Install the cable retainer on the left handle half Assemble the stop switch H on the throttle G F K H 2 Attach the connection plate J and the screw I below the stop switch H Use the correct torque see Servicing data on page 6 I J H 3 Attach the throttle wire E in the throttle trigger A Put the spring B into the hole L in the thro...

Page 40: ... G F C H A B D 5 Put the shaft in the left handle half and attach the right half with the screws and the nuts Make sure to use the correct torque see Servicing data on page 6 7 13 Gearbox 7 13 1 To remove the gearbox 1 Put a rod through the hole B to lock the axle J C Y A G F E D B H I 2 Remove the trimmer head A 3 Remove the support flange Y 4 Remove the protective plate C 5 Remove the screw D th...

Page 41: ...shaft assembly 6 Remove the input shaft assembly O from the gearbox T V U X P O S R Q P 7 Increase the temperature of the gearbox to approximately 140 C 8 Remove the bearing T on the output shaft If it is necessary hit the gearbox against a wooden block until the bearing falls out 9 Remove the the gear V and bearing X from the output shaft U 10 If it is necessary to replace the bearings R and Q re...

Page 42: ...position is attached 7 Make sure that the gearbox is approximately 110 C 8 Put the input shaft assembly into the gearbox with a pair of pliers or a sleeve 9 Attach the snap ring L for the bearing on the output shaft K L N M 10 Attach the bushing K on the output shaft 11 Attach the grease plug N 12 Attach the snap ring M for the bearings on the input shaft 13 Fill the gearbox with grease about 10 t...

Page 43: ...e carburetor is not attached correctly The lever arm of the needle valve does not operate correctly The idle speed is too low Defective heat insulation seal The lever arm of the needle valve is damaged The lever arm of the needle valve is too high The lever arm of the needle valve does not operate correctly The needle valve is worn Object in the needle valve groove The idle speed does not become s...

Page 44: ...ncorrect unsatisfactory fuel The needle valve is defective The carburetor is not attached correctly The lever arm of the needle valve is damaged The lever arm of the needle valve does not operate correctly The needle valve spring is damaged The needle valve spring is not attached correctly The needle valve is worn Object in the needle valve groove Increase and decrease speed The engine does not in...

Page 45: ... creased The lever arm of the needle valve is too high The lever arm of the needle valve does not operate correctly The needle valve is worn Object in the needle valve groove The engine cannot increase speed Defective heat insulation seal 1281 001 Troubleshooting 45 ...

Page 46: ...nt sound pressure level at the operator s ear measured according to EN ISO 11806 and ISO 22868 dB A min max 84 8 Vibration levels2 Equivalent vibration levels ahv eq at handles measured according to EN ISO 11806 and ISO 22867 m s2 Front handle m s2 4 6 Rear handle m s2 5 0 Product data Maximum rpm output shaft 7800 Output shaft thread mm M10x1 25 Lefthanded Tube diameter 26 Tube length 1430 Transm...

Page 47: ...1281 001 Technical data 47 ...

Page 48: ...1141483 26 2019 09 27 ...

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