® Power Chain Saw @ Stihl 070, 070 AV, 090, 090 AV, 090 G Models 1106, 1109 Chain Saw Service Manual This Chain Saw Service Manual relates to our models Stihl 070, 070 AV, 090, 090 AV, 090 G beginning with machine number 1 163 000 (070 + 070 AV + 090+ 080 AV) and machine number 1302500 (090 G), April 1969. Please refer to our periodically turned out Technical Informations for repairing power saws of same model but of older design and lower machine numbers than mentioned above and for technical @ rrediicavons made after thie manuel was printed This Guide Book should be used only for the instruction of our dealers and authorized service shops. Handing over or lending this manual to other persons is prohibited. Contents ®@ specitications 2 Saw Chain drive with clutch 5 Disassembly and repair, transmission 090 G Ignition system 9 Exposing armature plate, replacing set of points, testing and re-adjusting ignition timing Driving parts — cylinder with piston 2 ] Drooosensy srcnuing parts, decompression va, pressure testing crank-case Oil pump 7 Design and operation, disassembly, chain lubricating oils Rewind starter 18 Disassembly, assembly of a new starter rope, general hints for repair AV-handle 20 Carburetor 22 Design and operation, disassembly and repair, STIHL maintenance, carburetor adjustment, pressure testing carburetor, speed governor ‘Andreas Stihl Special tools 27 Postfach 1771 a -7050 Waiblingen‘Specifications Engine Fuel System STIHL single cylinder, two-stroke engine with specially impregnated cylinder bore © Displacement: 406 om (6.47 cu. in) (070, 070 AV, 090 6) 187 cm* (8.36 cu. in) (090, 090 AV) Bore: 58mm (2.28 in) (070, 070 Av, 090 G) {86 rm (2.60 in) (090, 090, AV) stroke: 40mm (1.57 in) Compression ratio: 9:1 Max. torque! 7.7 Nm (5.7 If. ) on 070, 070 AV,090G 8,5Nm (7.0 bf.) on 090, 090 AV atn=5000rp.m, Max. engine speed: 8000r.p.m. Mean idle speed: 2000 r-p.m, (070, 070. AV) ® +1800 p.m. (090, 090 AV, 0906) Crankshaft: Two-part, drop forged Crankshaft bearings: 2 needle bushes Crankpin dia: 19,0 mm (0.75 in) Big-end bearing: Needle cage Piston pin dia: 46,0 earn (0.59 in} ‘Small-end bearing: Needle cage Starter: Fawl system (070, 070 AV) Friction shoe system (080, 090 Av, 090.6) ®@ Dotn with automatic starter rape rewind mechanism Starter rope: 4.5mm (0.18 in) dia., 1000 mm (40 in) long Chute Centrifugal cluch with tining 78 mm (3.1 in) dia. (070, 070.AV) 96 mm (8.8 in ia. (090, 080 Av, 090 G) ® | Engagement speed: approx. 2600 rp.m. (070, 070 AV) | approx. 2500 n,m, i (090, 090 Av, 090 6) Leakage testing crankcase with overpressure’ 0,5 bar (71 Ibf/in?) with vacuum: 0,5 bar (74 Ibf/in®) Carburetor: Al-position diaphragm cartuuretor with integral fuel pump Adjusiment High-speed adjustment screw H: Low-speed adjustment screw L: Short with knurled head, open 1 turn Long, open turn {Basle sting, starting with ® screws hard against their seats)Ignition System Reduction gear (090 G only) Tightening Torques Leakage testing carburetor with overpressure Fuel capacity Fuel mixture: Air filter: pe Magneto edge gap: Air gap: Ignition timing: Spark advance: Breaker point gap: Condenser: ‘Armature: Spark plug (suppressed): ‘Type: Reduction: Lubrication: Oil capacity: Crankshaft nut (ignition side) M10x1. Crankshatt nut (clutch side) M10%1 left-hand thread: M6 nuts: MB8hex. head screws: M6 socket-head screws: M6 cheese-head screws: M5 socket-head screws Other M5 screws: M4 screws: Spark plug: 0,4 bar .7 totrin®) 0,821(1.73 pt) Mix ratio 1:40 with STIHL engine oil, 1:25 for other branded two-cycle engine oils Large area flocked wire mesh fiter Breaker-controlled magneto ignition system 7....1 mm (0.26. . .0.43in) 0.2...0,8mm (0.008. , 0.012 in) 2,8...3,2mm (O41 ...0426in) before TD.C. 27°. ..29° 0,35. . .0,45 ram (0.014. . .0.018in) Capacitance: 0,15... 0.19 uF Resistance of primary winding 05...0,60 Bosch WSR.6 F (earlier designation: WKA 200 TR 6) or Champion ROJ6Y Heat range: 175 (070, 070 AV, 090) 225 (090, 090 AV) Electrode gap: 0,6 mm (0.02 in) Spark plug thread: M 14x'1,25, 9,5 mm (0.37 in) long Single-speed spur gear box a HD SAE 30 engine oil 015 (0.32 pt) 45 Nm (332 Ib. tt) 44,1 Nm (92.5 Ib.) 6.9Nm_ (6.1 Ibf.tt) 9,8.Nm (72 Ibf.tt 9,8Nm (72 Ibt.tt 6.9Nm (64 Weft) 5 (2 IDEA) 4.9Nm (3.6 Ibf.tt) 2,5 Nim (1.8 Ibf.ft) Nm (183 bf.Cutting Attachment Weights Guide bars: Bar lengths: Chain: Chain sprocket: Chain speed: Chain lubrication: Oil tank capacity Dry weight without bar and chain 070: O70 AV: 090: 090 AV: 090 G: STIHL Duromatic with stelite tipped nose; STIHL Rollomatic with sprocket nose. Both types. with corrosion-resistant finish and induction hardened track Duromatic 53, 63. 75, 80, 90, 105, 120 and 150 om (21, 25, 30, 32, 96, 41, 47 and 49 in) Rollomatic 75, 90 and 105 om (80, 35 and 41 in) for 0.404" (10.26 mm) pitch 0.404" (10,26 mm) pitch for 070, 070 AVand O90 AN Ye" (12,7 men) pitch for 080 with wrap-around handle and 090 G T-tooth for 0.404" (10,26 mm) pitch 6-tooth for %"(12,7 mm) pitch 16,7 mis (64.8 ft/sec) with 0.404" (10,26 mm) chain at 7000 r.p.m. 17,8 m/s (58.4 ft/sec) with ¥2" (12,7 mm) chain at 7000 rp.m. (070/090) 8.9 m/s (29.2 ft/sec) with ye" (12,7 mm) chain at 7000 r.p.m, (0906) ‘Spaed controlled oil pump, operative only when chain is running Integral hand pump for additional ‘chain lubrication, Supplementary oil feed control by means of adjusting screw 0,531 (142 pt) 10.7 kg (236 Ib) 11.8kg (26.0) 11.5 kg (25.4 Ib) 12.3 kg (27.1 Ib) 19.4 kg (29.5 Ib)‘Sorewing In orank-shalt locking scrow Loosening crankshaft nut ‘ ®} Fo disossembling the chain drive with clutch remove serew plug Chain Drive with eluteh in crank-case and screw in crank-shaft locking screw, by hand, Disassembly and repain which you find in the tools kit, Turn clutch counter-clockwise until web of crank-shaft is stopped by the crank-shaft locking screw. This locks the crank-shaft and the hexagonal crank-shaft nut can now be removed with a 17 SW combination wrench by turning it clockwise. Note: Left-hand thread! Remove hexagonal nut, washer and ring and then chain sprocket, © cistch ond spider from eranleshaft A “Spieth" adapter sleeve is ingerted into the spider of the clutch which gets deformed when the hexagonal nut is tightened and this adapter sleeve ensures 2 tight connection between crank-shaft and spider. The friction linings of the clutch shoes get worn with the time. If the friction linings are worn so that the clutch shoes must be renewed only the whole set of clutch shoes can be replaced. The same applies to the clutch springs: only the whole set of springs can be replaced if a spring is broken or stretched When re-assembling the clutch remove ail traces of oil or grease from the friction linings — oil or grease on the friction linings would cause slipping of clutch and would reduce the effectiveness of the clutchExposed clutch End play contr of erank-shatt Installation ot spring Disassembly of clutch with chain sprocket Replacing new clutch shoes The chain drive sprocket is supported on the crank-shaft by a needle bearing (which should be greased with bearing grease every two months). The chain drive sprocket must be renewed if it has a wear of more than 04" = 1 mm depth. Moreover, the clutch retainer between chain sprocket and clutch is to be mounted in such a way that the radius, which you find at the centre bore is positioned at the engine side. Mount clutch with absolutely dry “Spieth” adapter sleeve, ring and washer and tighten hexagonal nut with a torque wrench to 32.5 Ibf. ft (44,1 Nm). Contrary to the models 070 and 070 AV, the clutch of the models 090, 090 AV and 090 G is composed of a spider and six clutch shoes. These clutch shoes are held in place by two springs which are positioned laterally in the recesses If the set of clutch shoes has to be replaced owing to worn friction linings insert the new clutch shoes into the mounting collar on the spider. Insert mounting bolt and press spring over mounting bolt (see illustration) into the recesses of the clutch shoes. This must be done from both sides.29 Contrary to the direct drive models 070, 070 AV, 090 and 090 AV the model 090 G (G = Transmission) 1¢ equipped with a spur wheel reduction gear which allows the use of guide bars up to 150 cm (60°) length, The reduction ratio is about 2: 1, that means the drive gear has 17 and the driven gear 35 teeth. The chain drive is posi- tioned about in the middle of the machine under the muffler. The model 090 G is equipped with a chain drive sprocket of '/2" pitch, Alternatively it can also be equipped with a chain drive sprocket of .404” pitch. It is pressed onto the drive shaft, secured by a fitting key and fastened by a hexagonal nut. After having removed the hexagonal nut the chain drive sprocket can be pulled ‘aff the drive shaft with a puller 1109 890 4401. Before reassembling the chain drive spracket you must heat it to about 90—100° C (194—-212° F). In this way it can be easily put on the drive shaft To disassemble transmission of the 090 G, drain gear oll from gear case. Disassemble transmission cover by removing the 11 cylin drical screws and the hex.-head screws at the wrap-around handle. For removing the transmission cover from the two adjusting pirs the cover is provided with three lugs. Remove screw plug from crank-case and screw in crank-shaft locking screw by hand, Transmission 090 G Disassembly of TransmissionTightening crank-shatt nut with torque wrench Lubrication Lever off cap on clutch drum with a screwdriver. This cap protects the clutch against lubricating oil. Loosen hexagonal crank-shaft nut with 17 SW combination wrench by turning it clockwise. Note: Left-hand thread! Then remove washer and ring. Now pull off clutch drum with drive sprocket and clutch with spider from crank- shaft. Remove bracket over the small spur gear by loosening the two cylindrical screws and remove spur wheel from crank-shaft. To loosen the hexagonal nut at chain sprocket hold sprocket with a pipe wrench. Then remove washer under sprocket and pull chain sprocket off shaft with puller 1109 890 4401 Now remove large spur gear with shaft from grooved bearing. Pull spur gear from sheft with a double-claw puller. Before reassembling the transmission check the oll seal, the grooved bearing in the crank-case, the needle bearing in the gear case cover, the needle bearing of the small spur gear and the needle bearing of the drive gear. The spur gears can be replaced individually. The transmission has an oil-bath ubrication. The gear oll is SAE 30 oil. The oll quantity amounts to 150 com (9.15 cu. inches). Refill oil through oil filler hole and check oil level at oil filler hole. The oil level is correct when the oil reaches the bottom edge of the oil filler hole with horizontally positioned engine, 2 ~@ The ignition spark is produced by a Bosch fly-wheel magneto which 's positioned under the rewind starter or under the fan whee! Unscrew the four AM 5 cylindrical screws at the fan cover with rewind starter, Disassemble fan cover. Remove fan wheel which is fastened by four screws. Now lock crank-shaft by removing the am screw plug and screwing crank-shaft locking nut into the screw plug hole. The crank-shaft locking screw is included In the tools kit, Then loosen hexagonal crank-shaft nit using a 17 SW combi- nation wrench by turning the nut counterclockwise. Remove starter cup. Screw fiy-wheel puller with pressure piece onto thread of fly- wheel until snug and turn fly-wheel clockwise until the web of the crank-shaft bottoms on the crank-shaft locking screw. Screw in pressure piece of fly-wheel puller to loosen the fly-wheel from crank-shaft taper and lift t off the crank-shaft. Now the armature plate is accessible. The point set and the condenser are positioned under the dust cap on the armature plate. Remove dust cap. Take out screw which holds the breaker point base to the armature plate and remove retaining ring from breaker arm shaft. Then loosen the screw: with nut connecting the ground Ignition system Exposure and Disassembly of Armature Plate lustrations: Exploded view: Removing starter cup and inserting ‘y-wheo! pullor 1 Hexagonal nut 2 Washer 3, Starter cup 4.Hex-head screw 5 Puller sleeve 5. Thrust bolt Disassembly of fan whee! ‘Remaving fiy whee! Replacing Point Set 9erg | i Removing rubber cap trom grommet Breaker points expased far adiustment Exposed ignition system Torque wrench Tightening hoxagonal out with torque wranch Checking and Re-adjusting Ignition Timing 10 lead and the lead to the ignition coil as well as the spring of the breaker arm. Now remove the point set and replace the whole set For this purpose reassemble the dust cap and place tly-wheel, starter cup and washer on crank-shaft, Make sure Woodruff key is correctly positioned in the keyway of the crank-shaft and the fiy-wheel. The Woodruff key should be absolutely grease free Tighten hexagonal nut. The correct torque of the crank-shaft nut is 33.2 lof. ft (45 Non) and should be checked with a torque wrench. Remove crank-shaft locking screw from crank-case and screw screw plug into the screw plug hole. Turn fly-wheel and check to be sure that there is no metal to metel contact between magneto and fly- wheel. Now remove rubber cap from dust cap and adjust breaker point gap to 0.4 mm (.016"). The adjustment of the breaker point gap should be made in the following way: Screw timing dial gauge into spark plug hole and turn fly-wheel in direction of engine rotation Until piston is at top dead centre. Now adjust timing dial gauge to “0” position. In this position the breaker point gap should be 0.4 mm 016"). Check to be sure that the breaker points face each ather correctly and that they lift in parallel position. Conneet one terminal of ignition timing device with the ground lead and the othr terminal with the ground. Now lower piston te 23.0 mm (0.12") before top dead centre by turning the fly-wheel in reverse direction of engine rotation (clockwise). Loosen the screws retaining the armature plate through opening in the fiy-wheel and turn armature plate counterclockwise if ignition timing is too much advanced, or clockwise if ignition timing is not enough advanced until pilot lamp of ignition timing device will indicate when the breaker points open. Re-tighten the retaining screws of armature plate, Re check timing to be sure adjustment is correct. When turning the flywheel in direction of engine rotation the pilot lamp should light up when piston is at 3.0 mm (0.12") before top dead centre. Use only @ correct spark plug (Bosch WSR 6 F) with a correct spark gap. Frayed or worn insulation of the breaker point base, the breaker points and the ground lead or fouled breaker points may cause short Circuits in the primary circuit of the ignition system. Therefore, abways inspect the ignition system for such shorts when repairing it. Furthermore, check to be sure that the ground lead does not cause a short circuit where itis connected with the breaker point base. in case of malfunction of the ignition system also check ignition switch, high tension lead and spark plug terminal. Connecting ignition dial gauge and “nition timing cevioe Tanition dial gauge Jonition timing deviee Looking for malfunction 1Crank-shatt 14 rollers, The bearing fits at the conrod are classified into two dimen- sion groups: 1. Green dimension group: Shaft 17, 996 — 18, 000 Conrod 24, 010— 24, 014 2 Red dimension group: Shaft 18, 001 — 18, 005 Conrod 24, 015—24, 019 The split needle cage can be replaced at will. The radial play of the crank-shaft in the needle cage is 0.010—0.018 mm (0.004—0.0072") f a worn or damaged needle bearing should necessitate the removal of the crank-shaft from the conrod re-use parts only if bearing sur- faces at crank pin and at conrod bearing are in perfect condition If these surfaces are rough, scarred or worn reject the whole crank- shaft. When installing the needle bearing check to be sure that the bearing surfaces of the Coe ©0 oo -— am