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7. AUTOMATIC DECOMPRESSION SYSTEM

EH09D and EH12-2D engines employ an automatic decompression system as a standard feature. This
enables easy starting of the engine, with lighter recoil pull.
The automatic decompression system releases the compression of the engine by lifting up the exhaust
valve at cranking speeds. The following is the explanation of how the system  works.

At the end of the compression process, the release lever lifts up the tappet which in turns opens up the
exhaust valve slightly to release the compression. The release lever has a flyweight on its end and
another end of the lever is a crescent cam.
When the engine is cranked, the crescent cam projects above the cam profile and lifts up the tappet
because the gravity force on the weight is larger than the centrifugal force on the weight.

When the cranking speed reaches a specified r.p.m., the crescent cam is retracted under the  cam profile
because the centrifugal force applied to the flyweight becomes larger than the force of gravity on the
weight and thus it is shifted to the position shown in the illustration below.

Fig. 7-1

Fig. 7-2

FLYWEIGHT

TAPPET

CRESCENT CAM

EXHAUST CAM

EXHAUST CAM

ROTATION

CAMSHAFT

RELEASE LEVER

FLYWEIGHT

TAPPET

CRESCENT CAM

EXHAUST CAM

EXHAUST CAM

ROTATION

CAMSHAFT

RELEASE LEVER

Summary of Contents for EH09D

Page 1: ...SERVICE MANUAL EH09 EH12 2 Rammer ENGINES Models PUB ES1330 Rev 12 01...

Page 2: ...Copyright 2001 Robin America Inc 940 Lively Blvd Wood Dale IL 60191 Phone 630 350 8200 Fax 630 350 8212 e mail sales robinamerica com www robinamerica com...

Page 3: ...9 GOVERNOR SYSTEM 9 4 10 COOLING SYSTEM 10 4 11 LUBRICATION SYSTEM 10 4 12 IGNITION SYSTEM 10 4 13 CARBURETOR 10 4 14 AIR CLEANER 11 4 15 DECOMPRESSION SYSTEM 11 4 16 SECTIONAL VIEW OF ENGINE 12 5 DIS...

Page 4: ...STOPS 67 10 4 ENGINE OVERHEAT 68 10 5 ENGINE KNOCKS 68 10 6 ENGINE BACKFIRES THROUGH CARBURETOR 68 11 INSTALLATION 69 11 1 INSTALLING 69 11 2 VENTILATION 69 11 3 EXHAUST GAS DISCHARGE 69 11 4 POWER TR...

Page 5: ...n o i t a c i r b u L e p y T h s a l p S t n a c i r b u L r e h g i h r o E S s s a l C 0 3 W 0 1 r o 0 3 0 2 E A S l i O e l i b o m o t u A t n a c i r b u L f o y t i c a p a C l a g S U 9 7 0 0...

Page 6: ...t a c i r b u L e p y T h s a l p S t n a c i r b u L r e h g i h r o E S s s a l C 0 3 W 0 1 r o 0 3 0 2 E A S l i O e l i b o m o t u A t n a c i r b u L f o y t i c a p a C l a g S U 1 1 0 s r e t...

Page 7: ...th SAE internal combustion engine standard test code J1349 2 2 CONTINUOUS RATED OUTPUT The continuous rated output is the output of an engine at optimum governed speed which is most favor able from th...

Page 8: ...4 PERFORMANCE CURVES 0 2000 0 1 2 3 6 0 6 0 5 0 4 5 4 1 2 N m kgf m HP kW TORQUE OUTPUT REVOLUTION r p m 3000 4000 MAXIMUM HORSEPOWER CONTINUOUS RATED HP MAXIMUM TORQUE RECOMMENDED HORSEPOWER RANGE E...

Page 9: ...5 0 1 2 3 1 2 3 0 7 0 8 0 6 4 2000 3000 4000 6 7 8 kW HP MAXIMUM TORQUE MAXIMUM HORSEPOWER OUTPUT TORQUE RECOMMENDED HORSEPOWER RANGE CONTINUOUS RATED HP N m kgf m REVOLUTION r p m EH12 2D...

Page 10: ...ration damping and durability are greatly improved by introducing a vibration proof breather mecha nism thick sheet metal reinforced casting parts with thick walls and ribs and a carburetor that pre v...

Page 11: ...IN BEARING COVER The main bearing cover is an aluminum die cast ing with thick reinforcing walls and ribs which is mounted on the output shaft side of the crank case Remove the main bearing cover to i...

Page 12: ...and the second ring are shown in the illustration The oil ring is designed for better sealing and less oil consumption 4 6 CAMSHAFT The camshaft is made of special cast iron and camshaft and gear are...

Page 13: ...8 CYLINDER HEAD The cylinder head is an aluminum die casting which utilizes wedge type combustion chamber for the high combustion efficiency Fig 4 7a Model EH09D IN EX INTAKE VALVE EXHAUST VALVE Fig...

Page 14: ...ling air capacity for the inlet and exhaust area and cylinder The cylinder baffle directs the cool ing air flow efficiently OIL SPLASHER IGNITION COIL FLYWHEEL Fig 4 12 FLOAT TYPE DIAPHRAGM TYPE 4 13...

Page 15: ...LEMENT SET PLATE AIR CLEANER CLEANER COVER CLEANER BASE ELEMENT URETHANE FOAM 4 15 DECOMPRESSION SYSTEM An automatic decompression mechanism which opens the exhaust valve before the piston reaches max...

Page 16: ...VIEW OF ENGINE Fig 4 15 INTAKE VALVE EXHAUST VALVE MUFFLER PISTON PISTON RING P T O SHAFT MAIN BEARING COVER ADAPTER FLANGE CRANKCASE CYLINDER HEAD PISTON PIN IGNITION COIL BLOWER HOUSING RECOIL STAR...

Page 17: ...13 Fig 4 16 ROCKER COVER ROCKER ARM SPARK PLUG CONNECTING ROD OIL GAUGE PLUG PUSH ROD CARBURETOR AIR CLEANER TAPPET CAMSHAFT STIFFENER GOVERNOR LEVER SPEED CONTROL LEVER CRANKSHAFT...

Page 18: ...14 Fig 4 17 INTAKE VALVE EXHAUST VALVE PISTON PISTON RING P T O SHAFT MAIN BEARING COVER CRANKCASE CYLINDER HEAD PISTON PIN IGNITION COIL BLOWER HOUSING RECOIL STARTER FLYWHEEL EH12 2D...

Page 19: ...15 Fig 4 18 ROCKER COVER ROCKER ARM SPARK PLUG CONNECTING ROD MUFFLER OIL GAUGE PLUG PUSH ROD CARBURETOR AIR CLEANER TAPPET CAMSHAFT GOVERNOR LEVER SPEED CONTROL LEVER CRANKSHAFT...

Page 20: ...ttached to them 2 Have boxes ready to keep disassembled parts by group 3 To prevent losing and misplacing temporarily assemble each group of disassembled parts 4 Carefully handle disassembled parts an...

Page 21: ...s STEP 1 STEP 2 EH09D p e t S e v o m e r o t s t r a P s e r u d e c o r p d n a s k r a m e R s r e n e t s a F 1 n i a r d l i o e n i g n E l i o n i a r d d n a g u l p n i a r d l i o e v o m e...

Page 22: ...b e v o m e r s c p 5 2 1 x 6 M D 9 0 H E s c p 2 8 x 6 M D 9 0 H E s c p 4 5 5 x 6 M D 2 2 1 H E EH09D EH12 2D M4 TAPPING SCREW 2 pcs CLAMP BLOWER HOUSING CP M6 x 8 FLANGE BOLT 4 pcs M6 x 55 FLANGE...

Page 23: ...e v o m e R g u l p k r a p s t e k s a g r e l f f u m e s o l o t t o n l u f e r a c e B t u n k c o l f l e s 8 M s c p 2 s c p 4 6 1 x 8 M 2 r e h s a w 8 M s c p s c p 2 8 1 x 6 M Fig 5 4 EH09D...

Page 24: ...e p i p r e h t a e r b e v o m e R s c p 2 t u n 6 M e c p 1 8 1 x 8 M D 2 2 1 H E CLEANER COVER CLEANER COVER PURSE LOCK BREATHER PIPE BREATHER PIPE M6 SELF LOCK NUT 2 pcs M8 x 18 BOLT AND SPRING W...

Page 25: ...5 2 x 6 M 8 r o t e r u b r a C g n i k o o h n u y l l u f e r a c r o t e r u b r a c e v o m e R r o n r e v o g m o r f g n i r p s d o r d n a d o r r o n r e v o g r e v e l 9 d n a r e v e l l...

Page 26: ...p g n i k o o h n u y l l u f e r a c r o t e r u b r a c e v o m e R r o n r e v o g m o r f g n i r p s d o r d n a d o r r o n r e v o g r e v e l s c p 2 t u n 6 M e c p 1 0 4 x 6 M 9 d n a r e v...

Page 27: ...f a h s k n a r c f o d n e l e e h w y l f n o p a T l e e h w y l f e v o m e r o t r a b m u n i m u l a 0 1 5 g i F e e S r e l l u p l e e h w y l f e h t g n i s u l e e h w y l f e v o m e R 1...

Page 28: ...n i l y C m o r f t e k s a g d n a d a e h r e d n i l y c e v o m e R 1 e s a c k n a r c r e d n i l y c m o r f s d o r h s u p e v o m e R 2 s c p 4 5 5 x 8 M D 9 0 H E s c p 4 5 6 x 8 M D 2 2 1...

Page 29: ...AY 8 pcs Fig 5 14 p e t S e v o m e r o t s t r a P s e r u d e c o r p d n a s k r a m e R s r e n e t s a F 5 1 r e v o c g n i r a e b n i a M l a e s l i o e h t e g a m a d o t t o n l u f e r a...

Page 30: ...n e t s a F 6 1 s t e p p a t d n a t f a h s m a C h s u p e d i s l e e h w y l f e h t n o e s a c k n r a c y a L e v o m e r d n a k c o l b e h t o t n i p u s t e p p a t t f a h s m a c d n a...

Page 31: ...o l a v o m e r h t i w e r e f r e t n i r e d n i l y c f o d n e r e p p u s c p 2 5 2 x 5 M D 9 0 H E s c p 2 4 3 x 6 M D 2 2 1 H E n i p n o t s i p d n a n o t s i P e v o m e r o t n i p n o t...

Page 32: ...d n a s k r a m e R s r e n e t s a F 8 1 t f a h s k n a r C t f a h s k n a r c f o d n e l e e h w y l f n o y l t h g i l p a T m o r f e v o m e r o t r e m m a h t f o s a h t i w e s a c k n a...

Page 33: ...o c t u o g n i r p s e v l a v d n a r e n i a t e r g n i r p s s e v l a v t s u a h x e d n a e k a t n i e v o m e R 2 d a e h r e d n i l y c m o r f e h t m o r f t i s o p e d m u g d n a n o...

Page 34: ...uts to specification refer to the TORQUE SPECIFICATIONS See page 76 7 Apply oil to rotating and sliding portions 8 Check and adjust clearances and end plays where specified in this manual 5 4 1 CRANKS...

Page 35: ...e MAG side of the connecting rod 2 Apply oil to the small end of connecting rod piston and piston pin before assembling Be sure to use clips on the both side of the piston pin to secure piston pin in...

Page 36: ...on M5 x 25 mm connecting rod bolt 2 pcs EH09D M6 x 34 mm connecting rod bolt 2 pcs EH12 2D 3 Check for free movement of connecting rod by turning crankshaft slowly Note 1 Apply enough oil to lubricate...

Page 37: ...on camshaft and install cam shaft in the crankcase See Fig 5 31a 5 4 6 ADJUST CRANKSHAFT END PLAY 1 Adjust end play to 0 2 mm 0 008 using the proper spacer The proper spacer may be determined in the f...

Page 38: ...SPACER CRANKCASE CRANKCASE MAIN BEARING COVER CP M6 x 30 BOLT AND WASHER AY 8 pcs 2 Lubricate the oil seal and bearing surfaces Coat the surface of the main bearing cover with sealant Three bond 1216...

Page 39: ...es and guides lap valves in place until a uniform ring shows around the face of the valve Clean valves and wash cylinder head thoroughly 5 Install cylinder head onto cylinder with new head gasket Tigh...

Page 40: ...ER AY 4 pcs 5 4 8 ROCKER ARMS AND PUSH RODS 1 Insert push rods into crankcase Put push rod tip in the hollow of tappet top Note An oil return slot is located next to the tappet boss If you do not put...

Page 41: ...the nut under the rocker arm and turn the bolt pivot to adjust the clearance between rocker arm and valve stem end Tighten the nut on rocker arm 3 Install rocker cover and gasket Rocker cover M6 x 25...

Page 42: ...EH12 2D e u q r o t g n i n e t h g i T D 9 0 H E D 2 2 1 H E N 1 9 4 2 4 4 m g k 0 0 5 0 5 4 m c t f 2 6 3 5 2 3 b l N 0 3 6 0 9 5 m g k 0 5 6 0 0 6 m c t f 0 7 4 0 3 4 b l D 9 0 H E e u q r o t g n...

Page 43: ...37b Model EH09D Model EH12 2D 5 4 13 INTAKE PIPE INSULATOR EH12 2D 1 Install the intake pipe to the cylinder head with gasket M6 flange nut 2pcs M6 x 40 mm bolt and washer 1pce Then put the gasket an...

Page 44: ...and gaskets for carburetor to cylinder head 6 Install carburetor to cylinder head hooking governor rod to governor lever and throttle lever of carbu retor Hook rod spring over governor rod 7 Attach ai...

Page 45: ...intake pipe hooking governor rod to governor lever and throttle lever of carbure tor Hook rod spring over governor rod 6 Attach air cleaner base to carburetor Tighten two flange nuts and a bolt Connec...

Page 46: ...governor spring and carburetor throttle valve is fully open 3 Turn the governor shaft clockwise all the way using a screw driver and tighten lock bolt to secure the lever on the shaft 4 Loosen the se...

Page 47: ...nut 2 pcs M6 x 12 mm bolt and washer 2 pcs 3 Finally tighten the self lock nut etc fully according to the following priority 1 1 1 1 1 M6 self lock nut 2 pcs 2 2 2 2 2 M6 x 12 mm bolt and washer 2 pc...

Page 48: ...ing priority 1 1 1 1 1 M8 self lock nut 2 pcs 2 2 2 2 2 M8 x 16 mm bolt and washer 2 pcs 3 3 3 3 3 M8 x 16 mm bolt and washer 2 pcs 4 4 4 4 4 M8 x 18 mm flange bolt 2 pcs Fig 5 41b 8 M e u q r o t g n...

Page 49: ...blower housing to crankcase Tighten five flange bolts M6 x 12 mm flange bolt 5 pcs Insert the high tension cord from the ignition coil into the notch of the blower housing so as not to pinch the cord...

Page 50: ...he electric current I2 flows 5 5 BREAK IN OPERATION A new engine or an engine that has been completely overhauled by being fitted with a new piston rings valves and connecting rod should be thoroughly...

Page 51: ...allowing the current I1 to bypass as current I6 At this moment the power transistor turns OFF and the current I2 is abruptly shut off resulting in the high voltage generated in the secondary coil whi...

Page 52: ...48 6 3 WIRING DIAGRAM STANDARD Fig 6 2...

Page 53: ...lever has a flyweight on its end and another end of the lever is a crescent cam When the engine is cranked the crescent cam projects above the cam profile and lifts up the tappet because the gravity f...

Page 54: ...on The fuel flows from the fuel tank into the float chamber through the needle valve When the fuel rises to a specific level the float rises and when its buoyancy and fuel pressure are balanced the ne...

Page 55: ...pplied to the engine 8a 1 4 CHOKE The choke is used for easy starting when the engine is cold When the starter is operated with a closed choke the negative pressure applied to the main nozzle increase...

Page 56: ...to the body Otherwise the fuel may become too rich and cause engine malfunction b The bolt 0 0 0 0 0 tightening torque is 90 kg cm Be sure to set the gasket 5 5 5 5 5 and washer 4 4 4 4 4 for chamber...

Page 57: ...ion The fuel flows from the fuel tank into the float chamber through the needle valve When the fuel rises to a specific level the float rises and when its buoyancy and fuel pressure are balanced the n...

Page 58: ...to the engine 8b 1 4 CHOKE The choke is used for easy starting when the engine is cold When the starter is operated with a closed choke the negative pressure applied to the main nozzle increases and...

Page 59: ...n nozzle 5 5 5 5 5 3 Reassembly a Fasten the main jet and main nozzle securely to the body Otherwise the fuel may become too rich and cause engine malfunction b The bolt 2 2 2 2 2 tightening torque is...

Page 60: ...through the fuel pump valve 3 FUEL INLET The fuel inlet is the opening through which fuel is sucked from the fuel tank 4 INLET VALVE The inlet valve opens when the diaphragm is submitted to the actio...

Page 61: ...11 METERING LEVER The metering lever has the function of opening shutting the inlet needle valve by transmitting the move ments of the metering diaphragm to that valve 12 METERING LEVER SPRING The met...

Page 62: ...at a high speed position 18 MAIN NOZZLE The main nozzle is the hole through which fuel is ejected when the engine is operating at high speed and when the throttle is at a high speed position 19 VENTU...

Page 63: ...or the like and blow it with compressed air However make sure not to blow compressed air into the check valve unit of the carburetor equipped with primer pump 2 Check the gaskets for any deformation a...

Page 64: ...them gently clockwise to the fully shut position and then adjust them to the specified opening by returning them counterclockwise from that position Be particularly careful when carrying out this adj...

Page 65: ...pecified idling speed 4 Next turn the idle needle 0 0 0 0 0 counterclockwise for the engine to operate at the specified idling speed 8c 5 2 HIGH SPEED ADJUSTMENT 1 Set the throttle valve 6 6 6 6 6 at...

Page 66: ...rope out of the reel unfasten the knot and pull it off to the di rection of the starter knob 2 persons re quired 5 By controlling the reel with the thumbs of both hands unwind the rope gently until t...

Page 67: ...ose to pop up redo the steps of 3 1 and 3 2 again WARNING Do not drop or shake the reel and put it on a level table because there is a spring set in the disassembled reel Disassembly is complete WARNI...

Page 68: ...ghtly by hand so that the ratchet guide won t move and tighten the set screw 4 Storing the spring power 1 Hold the case tight and using both hands wind up the reel counterclockwise 6 times 2 Set the r...

Page 69: ...your hand off the reel gently and re lease the rope slowly checking the wind ing power of the spring until the knob reaches the rope guide Assembly is complete Fig 9 9 ABOUT 20mm 6 Test the operation...

Page 70: ...pen by dirt or gum This trouble can be detected as the fuel flows out of the carburetor when the engine is idling Overflow This trouble may be remedied by lightly tapping the float chamber with the gr...

Page 71: ...irty or wet 5 Spark plug electrode gap incorrect 6 Spark plug electrodes are connected or bridged 7 Incorrect spark timing 8 Proper connection of all wires 10 2 ENGINE MISFIRES 1 Incorrect spark plug...

Page 72: ...tricted or carbon deposits in the combustion chamber 9 Engine running on low octane gasoline detonates due to heavy load at low speed 10 5 ENGINE KNOCKS 1 Poor quality gasoline 2 Engine operating unde...

Page 73: ...n of the hot air used for engine cooling and temperature rise of the machine Keep the engine room temperature below 50 C even in the hottest period of the year 11 3 EXHAUST GAS DISCHARGE Exhaust gas i...

Page 74: ...E D T S t i m i L D A E H R E D N I L Y C s s e n t a l F N A H T S S E L 5 0 0 2 0 0 0 1 0 4 0 0 0 h t d i w t c a t n o c t a e s e v l a V X E N I 0 1 7 0 9 3 0 0 8 2 0 0 0 2 9 7 0 0 a i d e d i s...

Page 75: ...9 6 2 1 5 0 5 2 1 5 5 8 1 0 2 7 7 1 0 2 o t t i D 9 6 2 0 6 0 5 2 0 6 8 2 7 3 2 0 2 7 3 2 o t t i D t s 2 g n i r o b e r 9 1 5 1 5 0 0 5 1 5 3 8 2 0 2 6 7 2 0 2 9 1 5 0 6 0 0 5 0 6 6 2 8 3 2 9 1 8 3...

Page 76: ...5 1 0 6 0 0 0 g n i r l i O 5 6 0 0 0 1 0 0 6 2 0 0 0 4 0 0 0 0 5 1 0 6 0 0 0 5 7 0 0 0 2 0 0 0 3 0 0 0 8 0 0 0 0 5 1 0 6 0 0 0 9 0 0 1 1 1 9 9 0 1 4 3 3 4 0 7 2 3 4 0 5 3 0 1 1 4 4 3 4 0 2 0 0 3 1 1...

Page 77: ...0 5 1 0 0 0 2 0 8 0 0 0 6 4 0 0 0 2 0 0 8 1 0 0 0 8 0 0 0 0 2 0 8 0 0 0 1 2 0 1 1 0 1 0 1 1 9 3 3 4 0 5 3 3 4 0 8 0 1 1 2 6 3 4 0 1 2 0 3 1 0 1 0 3 1 6 2 1 5 0 2 2 1 5 0 8 0 3 1 0 5 1 5 0 9 2 0 0 0 1...

Page 78: ...E V L A V a i d e d i s t u o m e t s e v l a V m e t s e v l a v n e e w t e b e c n a r a e l C e v l a v d n a a i d e d i u g e c n a r a e l c e v l a V N I 5 5 4 5 0 4 4 5 8 4 1 2 0 2 4 1 2 0 5...

Page 79: ...7 0 4 1 3 0 4 3 1 3 0 5 1 0 8 0 0 0 8 6 5 1 3 0 0 5 1 3 0 5 1 0 8 0 0 0 8 6 5 1 3 0 0 5 1 3 0 5 5 0 0 5 2 0 0 2 2 0 0 0 0 1 0 0 0 5 5 0 0 5 2 0 0 2 2 0 0 0 0 1 0 0 0 H T G N E L E E R F G N I R P S E...

Page 80: ...l o b p a c D 9 0 H E 8 7 9 5 0 8 0 6 7 5 3 4 D 2 2 1 H E 0 1 1 8 8 5 1 1 0 9 3 8 5 6 t u n l e e h w y l F D 9 0 H E 1 9 4 2 4 4 0 0 5 0 5 4 2 6 3 5 2 3 D 2 2 1 H E 0 3 6 0 9 5 0 5 6 0 0 6 0 7 4 0 3...

Page 81: ...c e n e c a l p e r r o s r e n e t s a f n e t h g i t e r f i n e t h g i t e r d n a e r a w d r a h e s o o l r o f t c e p s n I 3 y r a s s e c e n n i t l u s e r d n a f f o e m o c y a m s t...

Page 82: ...n a s g n i r n o t s i p e c a l p e R r a e y a e c n o s e n i l l e u f e c a l p e R 2 e g a k a e l l e u f y b d e s u a c s d r a z a h d i o v A 13 4 EVERY 100 200 HRS MONTHLY MAINTENANCE 13...

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Page 84: ...PRINTED IN THE USA...

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