Page 1 Maintenance Manual YG125-30A Chongqing YINGANG technology group co., LTD https://www.motomanuals.net/...
Page 2 YG125-30A Maintenance Manual [Foreword] Foreword This maintenance manual is only for the use of YINGANG repair shop. This manual is not available for all knowledge about motorcycles, only for maintenance and maintenance of YG125-30A. The aim is to understand maintenance principles, maintenance procedures and maintenance skills.
Page 3: Table Of Contents
YG125-30A Maintenance Manual Overview Contents Chapter 1overview…………………………………………………………………1 ……………………………………………………………………… 1 1.1 Overview 1.2 Lubrication system … ……………………………………………………………13 …………………………………………………… 24 1.3 Inspection and adjustmen ………………………………………………40 …… Chapter 2 Engine……… 2.1 Fuel system ………………………………………………………………………… 40 2.2 Removal and installation of engine ……………………………………………… 46 2.3 Cylinder head, cylinder and piston …………………………………………………51...
Page 4: Overview
YG125-30A Maintenance Manual Overview 1、Overview Engine Number Position Bar Tool About Motorcycle Maintenance Maintenance Period Table Technical Data of Main Performance Symbol Descriptions Standard Torque Values Engine Number Position Photo of Complete Vehicle: Frame Number Position: Engine Number Position: Engine Number Frame Number https://www.motomanuals.net/...
Page 5 YG125-30A Maintenance Manual Overview Maintenance Precautions To disassemble and assemble a motorcycle, Whenever reassembling after being disassembled, special service tools (SST) and general-purpose replace new washers, sealing members, etc. tools must be used in accordance with relevant regulations. While fastening bolts or nuts, proceed in diagonal...
Page 6 YG125-30A Maintenance Manual Overview The connector shall be fully inserted in place. For a connector with lock, confirm whether the lock is completely fixed. Make sure the harness is not falling off In case the fuse is blown, check for the causes and,...
Page 7 YG125-30A Maintenance Manual Overview 13. The clamp shall reliably bite the wire harness The wire harness shall not be slackened or be forcibly pulled. Do not pull! In case of a welded clamp, it shall not bite the wire If the wire harness has to contact the edge or sharp...
Page 8 YG125-30A Maintenance Manual Overview 14. When wiring, note when turning it leftwards or 18. Do not forcibly twist or forcefully bend the cable. rightwards to the limit position, the wire harness Because a deformed or damaged cable is the shall not be tightened up or slackened, and make cause of bad operation and damage.
Page 9 YG125-30A Maintenance Manual Overview Technical Data of Main Performance Item Data Length 2050mm Width 750mm Height 1040mm Wheelbase 1360mm Min. ground clearance 200mm Complete vehicle weight Non-loaded weight: 128kg, Curb weight: 136kg, Frame type Cradle type Rake angle 26° Front suspension device spring &...
Page 10 YG125-30A Maintenance Manual Overview Clutch Wet clutch, coil clutch, paper friction wafer Clutch operating system Manual mechanical Variable speed gear 5-speed constant mesh Primary reduction ratio 3.35 Ⅰ 3.077 Transmission gear ratio Ⅱ 1.789 Ⅲ 1.304 Ⅳ 1.091 0.929 Final reduction ratio 3.333...
Page 11 YG125-30A Maintenance Manual Overview Standard Torque Values ENGINE Thread diameter Item Quantity Torque value (N.m) Thread locker (mm) Cylinder head cover connecting bolt 8～12 40～50 Cylinder bolt 8～12 Valve adjusting screw nut 8～12 Timing driven sprocket bolt 7～11 Rocker-arm shaft cover 24～28...
Page 12 YG125-30A Maintenance Manual Overview Name and dimensions Torque value (N.m) 4.5 ～6 5mm bolt & nut 8 ～12 6mm bolt & nut 18 ～25 8mm bolt & nut 30 ～40 10mm bolt & nut 50 ～60 12mm bolt & nut 3.5 ～5...
Page 13 YG125-30A Maintenance Manual Overview Magnetic generator rotor puller: for dismantling Rubber hanner, Iron hammer, Copper hammer magnetic generator rotor Feeler gauge: to measure the clearance of piston, Micrometer: to measure the dimensions of piston, piston cylinder, valve, etc. pin, etc.
Page 14 C: Cleaning. R: Replacement. A: Adjustment. L: Lubrication. * This item is subject to maintenance by persons from YINGANG TECNOLOGY Service Station. If the user has special service tools, maintenance accessories or maintenance ability, it can repair it by itself.
Page 15 YG125-30A Maintenance Manual Overview YINGANG TECNOLOGY Service Station. Symbol Descriptions Meanings of various symbols in this manual: Explanation Measures to be prompted during operating, inspecting and maintaining. NOTICE: Special instructions or disposal measures given to prevent motorcycle from being damaged.
Page 16: Lubrication System
Lubrication system YG125-30A Maintenance Manual 2、Lubrication system Maintenance notice Inspection of lubricating oil Troubleshooting Replacement of lubricating oil Lubricating Position of Complete Vehicle Cleaning of Lubricating Oil Strainer Lubrication of Control Lines Cleaning and Replacement of Lubricating Oil Filter Engine Lubrication System Diagram...
Page 17 Lubrication system YG125-30A Maintenance Manual Troubleshooting ● ● Lubricating oil contaminated Lubricating oil consumes too fast 1. Fail to replace lubricating oil according to the There is leakage with the engine; maintenance period table; The piston ring is worn. 2. The pouring orifice thread is damaged thus causing The inlet/exhaust valve guide is worn;...
Page 18 Lubrication system YG125-30A Maintenance Manual Engine Lubrication System Diagram Camshaft oil through Cylinder head oil through Crankshaft oil through Cylinder oil through Oil filter Spindle oil through Oil pump Oil strainer Countershaft oil through https://www.motomanuals.net/...
Page 19 Lubrication system YG125-30A Maintenance Manual Cylinder block, cylinder head, camshaft bearing seat and a Left crankcase body oil through camshaft oil through Replacement of lubricating oil While replacing lubricating oil, it shall be carried out before the engine has cooled down. This will ensure quick and complete discharge of the engine oil inside the crankcase.
Page 20 Lubrication system YG125-30A Maintenance Manual CAUTION Application of engine oil of poor quality will have an impact on the functional performance and life span of the motorcycle engine. Cleaning of Lubricating Oil Strainer It shall be carried out while replacing lubricating oil.
Page 21 Lubrication system YG125-30A Maintenance Manual Oil Pump In case of failure, the oil pump needs to be removed for repair or replacement. This section includes the following contents: Steps and illustration for oil pump removal; Steps and illustration for oil pump installation;...
Page 22 Lubrication system YG125-30A Maintenance Manual Steps for oil pump installation: The installation procedures are the removal procedures in reverse order. Pay attention to the following points during the installation: 1、 The spare parts shall be clean and intact； 2、 Install clutch assembly, and the retaining nut M18 shall be coated with thread retaining adhesive LOCTITE243;...
Page 23: Inspection And Adjustmen
Inspection and adjustment YG125-30A Maintenance Manual 3、Inspection and adjustment Maintenance notice Brake system Spark plug Running system Lubricating oil Clutch control line Oil output tank Driving chain Timing phase Battery Checking Cylinder pressure Replacement of Fuse Timing chain tension Brake lamp adjustment...
Page 24 YG125-30A Maintenance Manual yellow line will be revealed at the crack point. Explanation: Unless expressly stated or indicated in the maintenance period table, check and adjust all parts of the YG125-30A motorcycle according to the contents hereof before using it. Technical specifications ●...
Page 25 Inspection and adjustment YG125-30A Maintenance Manual Spark Plug Lubricating oil Remove the spark plug cap. Remove the spark plug with Park the motorcycle on a flat surface, let the engine stop a socket wrench. Visually check whether there is any...
Page 26 Inspection and adjustment YG125-30A Maintenance Manual Timing phase While aligning It shall be carried out when the vehicle is new or there is any question about the timing phase. Remove the cylinder head cover Turn the crankshaft pulley Counterclockwise to align the scale line “I”...
Page 27 Inspection and adjustment YG125-30A Maintenance Manual The main reasons for insufficient cylinder pressure care not let the sealing washer and so on fall into the include: crankcase. Insert the tensioner 4 locking key into Incorrect valve clearance adjusted the tail end of the new chain tensioner, turn and retract ...
Page 28 Inspection and adjustment YG125-30A Maintenance Manual Valve clearance the top of the crankcase cover, and both intake and exhaust rock arms do not move but stop at their loosest Notice: position, which shows that the piston is in its top dead While adjusting the valve clearance, the engine shall center position of the compressing stroke.
Page 29 Inspection and adjustment YG125-30A Maintenance Manual Idle speed Air filter Notice Cleaning and replacement of air filter  Remove the left side covers Handle it carefully to Check and adjust the idle speed after all other items avoid scraping. of the engine have been adjusted to the specified ...
Page 30 Inspection and adjustment YG125-30A Maintenance Manual If the fine adjustment is not satisfying, separate the throttle control line with throttle valve body and unscrew the retaining nut B to make adjust the free stroke in a larger range. Screw up the retaining but B after the adjustment.
Page 31 Inspection and adjustment YG125-30A Maintenance Manual bleed air from the deflating valve of the brake caliper with Actuate the front brake handle a vacuum pump, and then refill brake fluid into the cylinder. When the vacuum pump has fully exhausted the air...
Page 32 Inspection and adjustment YG125-30A Maintenance Manual shoe has touched the wear limit and also on the brake cam alignment, shows the brake shoe has been touched the wear limit. Please change it. （2）If it needs to be changed. Please go to the designated special maintenance station.
Page 33 Inspection and adjustment YG125-30A Maintenance Manual Clutch control line specs Front tire Rear tire Clutch is the key part of transmitting power in motorcycle 110/90-17 130/80-17 transmission system，should adjust it according to the Cold tire air Front tire Front tire pressure following overhauling content．The content is the free...
Page 34 Inspection and adjustment YG125-30A Maintenance Manual remount it, and then mount the clutch control line, finally If the chain is too loose or too tight, make adjustment. adjust it to a satisfied free stroke according to the fine Adjusting methods: adjustment.
Page 35 Inspection and adjustment YG125-30A Maintenance Manual Cleaning and coating oil supply. Seriously corroded conductor connectors of the battery shall be replaced. Notice This model uses the oil seal chain, so the selected washing oil shall be in corrosive to the oil seal; while...
Page 36 Inspection and adjustment YG125-30A Maintenance Manual Replacement of Fuse cause serious hurt to skin and eyes by contact. Set the ignition switch to “OFF” position. The specified In case of contact with it, wash it off for 5 minutes and see a doctor immediately.
Page 37 Inspection and adjustment YG125-30A Maintenance Manual  Loose the screw to disassemble the headlight.  Rotating , directly unplugging  Rotating and disassemble the bulb.  Install the new bulb in reverse order Headlight bulb 12V55W Front and rear lamp bulb ...
Page 38 Inspection and adjustment YG125-30A Maintenance Manual Suspension system Bolts, nuts and fasteners Front suspension All the bolts, nuts and fasteners shall be screwed up as Make the front brake in braking state and press the front per the maintenance period table. And check all the cotter fork bracket for several times, and check the front pins, safety gripping gears, locks, etc.
Page 39 YG125-30A Maintenance Manual Fuel system 4、Fuel system Fuel tank Inlet pipe Throttle valve body Fuel pump Air filter https://www.motomanuals.net/...
Page 40: Fuel System
YG125-30A Maintenance Manual Fuel system Fuel system Maintenance notice Disassembly and assembly of fuel tank Troubleshooting Removal and installation of air filter Removal and installation of fuel tank Removal and installation of carburetor Maintenance notice This section introduces the knowledge related to the fuel system.
Page 41 YG125-30A Maintenance Manual Fuel system Installation steps Removal and installation of fuel tank Disassemble step The installation procedures are the removal procedures in reverse order. Remove the seat While installing, note that the wiring of the fuel pump control wire shall be in strict accordance with the wiring diagram.
Page 42 YG125-30A Maintenance Manual Fuel system Remove and installation of throttle body Installation steps： Disassemble step： The installation procedures are the removal procedures in reverse order. While installing, the locating slot must be Removal of rear wheel aligned with the locating lobe of throttle body Warning: Do not further disassemble the removed throttle body;...
Page 43 YG125-30A Maintenance Manual Fuel system Aintenance of Air Cleaner Component Damage form Trouble symptom of motorcycle Repair method description The engine is difficult to start．Insufficient engine output；Poor performance of engine C1ean the filtering Too much dust deposit during idle run．Excessive fuel element．c1ean...
Page 44 YG125-30A Maintenance Manual Removal and installation of engine 5、Removal and installation of engine https://www.motomanuals.net/...
Page 45: Removal And Installation Of Engine
YG125-30A Maintenance Manual Removal and installation of engine Removal and installation of engine Maintenance notice Installation of engine Removal of engine Maintenance notice It is only necessary to remove the engine from the frame when performing maintenance on the engine’s crankshaft, balancing shaft, driving parts, etc.
Page 46 YG125-30A Maintenance Manual Removal and installation of engine Removal of engine Detach the earth wire from the negative pole of the Park the motorcycle on the plane ground, and battery. completely drain the engine lubricating oil. Screw plug for oil draining...
Page 47 YG125-30A Maintenance Manual Removal and installation of engine 11. Remove the gear shift pedal and left rear cover.  Remove the rear absorber and rear fork 12. To remove the rear brake pedal connecting bolt;  Unscrew the nut and take out the rear fork shaft;...
Page 48 YG125-30A Maintenance Manual Removal and installation of engine Remove the drive chain Move the engine slowly from the right. https://www.motomanuals.net/...
Page 49 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston 6、Cylinder head, cylinder and piston Cylinder head cover Cylinder head Cylinder https://www.motomanuals.net/...
Page 50: Cylinder Head, Cylinder And Piston
YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Cylinder head, cylinder and piston Maintenance notice Cylinder head Troubleshooting Cylinder Cylinder head cover Piston Camshaft Maintenance notice The lubrication of the camshaft and rocker arm is implemented by pumping oil by the oil pump through the oil troughs of the cylinder, cylinder head and cylinder head cover;...
Page 51 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Top planeness 0.05 φ52.37～φ52.39mm mm φ52.37mm Piston external diameter Fit clearance with 0.01mm～0.04mm 0.04mm cylinder Piston and piston φ12.995mm～φ13mm φ12.995mm Piston pin external diameter φ13.002mm～φ13.008mm φ13.008mm Piston pin hole inside diameter Fit clearance 0.002mm～0.013mm...
Page 52 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Troubleshooting  ● Excessive noise Low cylinder pressure Valve: Incorrect valve adjustment; Incorrect valve clearance adjusted; Valve jammed or valve spring broken; Valve ablated or bent; Camshaft worn or damaged; Valve sealing failure;...
Page 53 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Cylinder head cover with a valve clearance adjusting tool as required. To remove the cylinder head cover: Mount the valve cover, etc Remove the lower / upper eyehole covers and turn the crankshaft so that the piston is at the upper dead point of the compression stroke.
Page 54 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Camshaft To remove the camshaft: Remove the lower / upper eyehole cover and turn the crankshaft so that the piston is at the upper dead point of the compression stroke. Strip the timing chain from the timing driven sprocket, and remove the timing driven sprocket.
Page 55 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Camshaft inspection Check the camshaft for abrasion, damage, oil through jamming, etc. and check whether the decompressor flying block can rotate and return smoothly. Measure the maximum IN / EX lift. Maintenance limit: IN≥≥5.5057mm, EX ≥ 5.515mm Max.
Page 56 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Pull off the spark plug cap, Installation is in the reverse order of removal. Precautions for installation: Confirm the location pin; clean all parts and components, and check whether the cylinder head oil through is unobstructed, clean and free of leak.
Page 57 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston The spark plug must be tightened to the specified tightening torque of 15～20N.m for fear of leak. While mounting the intake / exhaust valve, coat the mixture of engine oil and molybdenum disulfide on valve stem for preliminary lubrication.
Page 58 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Cylinder head inspection Measure the width of the valve contacting surface. Maintenance limit: ≤1.7mm Check whether the cylinder head is unobstructed, clean and free of leaks; check the cylinder head’s spark plug hole and valve seat for cracks;...
Page 59 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Cylinder inspection Check the cylinder for abrasion or damage, and check the cylinder wall for scratch. Whether the cylinder wall is scratched Notice: Do not drop the location pin into the crankcase.
Page 60 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Piston Mount the cylinder (See Installation of cylinder). To remove the piston: Mount the cylinder head (See Installation of cylinder Remove the cylinder head cover (See Removal of head); cylinder head cover) Mount the camshaft (See Installation of camshaft).
Page 61 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Notice: Do not damage the piston pin and piston ring. Do not reverse the mounting position of the first ring (ATG marker) and second ring (A marker). With side with marker face the top of...
Page 62 YG125-30A Maintenance Manual Cylinder Head, Cylinder and Piston Piston inspection Measure the piston pin external diameter. Check the piston for abrasion or damage, cracks, etc. and Clearance gauge Maintenance limit: ≥φ19.98mm check the skirt section for scratch. Measure the piston external diameter at the position Work out the clearance between the cylinder and piston.
Page 63: Clutch And Right Crankcase Cover
YG125-30A Maintenance Manual Clutch and Right crankcase cover Clutch and Right crankcase cover Clutch Engine Right crankcase cove https://www.motomanuals.net/...
Page 64 YG125-30A Maintenance Manual Clutch and Right crankcase cover Clutch and Right crankcase cover Maintenance notice Clutch Troubleshooting Right crankcase cover Maintenance notice To carry out the maintenance stated herein, it is unnecessary to detach the engine from the frame. However, the engine lubricating oil must be discharged.
Page 65 YG125-30A Maintenance Manual Clutch and Right crankcase cover Troubleshooting  Clutch In case of clutch operation failure, a better correction may usually achieved by adjusting the clutch handle free stroke.  Clutch slipping while accelerating Insufficient free stroke; Clutch disc abrasion;...
Page 66 YG125-30A Maintenance Manual Clutch and Right crankcase cover Right crankcase cover To install the right crankcase cover: To remove the cylinder head cover: Confirm the location pin; clean up the residual Remove the oil drain plug to drain the engine oil sealing paper gaskets on the right crankcase and inside the crankcase.
Page 67 YG125-30A Maintenance Manual Clutch and Right crankcase cover Adjust the direction of the clutch operating lever, Mount the clutch operating lever, rear brake return spring, cotter pin, rear brake lamp switch, etc. Refill engine oil. Notice: Do not scrape the crankshaft oil seal.
Page 68 YG125-30A Maintenance Manual Clutch and Right crankcase cover Disassemble and assemble of right crankcase cover Procedure Quantity Remarks Removing order Installation is in the reverse order of removal Right crankcase cover Right crankcase cover sealing paper gasket Replace it with a new one while assembling...
Page 69 YG125-30A Maintenance Manual Clutch and Right crankcase cover Clutch To install the clutch: To remove the clutch: Mount the clutch washer with the sabotage side Remove the right crankcase cover (See “Removal of facing the main shaft right bearing. right crankcase cover").
Page 70 YG125-30A Maintenance Manual Clutch and Right crankcase cover Mount the clutch push rod with the clutch push rod assembler Assemble the right crankcase cover by turning the clutch push rod until its rack side faces the crankshaft. (See “Installation of right crankcase cover").
Page 71 Removal / Installation of Clutch Procedure Quantity Remarks Removing order Installation is in the reverse order of removal Tightening torque 12N.m. clutch bush clutch assembly Nut M14*1 Flat washer Deep groove ball Gum base, soaking oil while assembling bearing Clutch out cover Clutch lug washer Clutch center bush Clutch friction plate...
Page 72 damage will occur. Explanation: While unscrewing bolt, do it in a crossing way twice or thrice. Do in the same way for screwing up bolt. Procedure Quantity Remarks Removing order Installation is in the reverse order of removal Tightening torque 12N.m. clutch bush clutch assembly Nut M14*1...
Page 73 Clutch inspection Check whether the housing splice has scars or cuts Measure the free length of the clutch spring. Maintenance limit: ≥41.3mm. due to the collision of clutch disc. Inspection Clutch spring free length measurement Vernier calipers Are there scars or cuts? Check the clutch disc.
Page 74 YG125-30A Maintenance Manual Magneto and starting system 8、Magneto and starting system Idle gear Double-linked gear cover Left front cover Rotor assembly Double-linked Gear Disk gear Engine https://www.motomanuals.net/...
Page 75: Magneto And Starting System
YG125-30A Maintenance Manual Magneto and starting system Magneto and starting system Maintenance notice Rotor assembly Left front cover Starting motor and starting transmission system Maintenance notice To carry out the maintenance stated herein, and the engine lubricating oil must be drained.。...
Page 76 YG125-30A Maintenance Manual Magneto and starting system Left front cover To remove the left front cover: Remove the gear shift pedal and left rear cover, and separate the magneto lead connector with the main cable. Gear shift pedal Left rear plate...
Page 77 YG125-30A Maintenance Manual Magneto and starting system Disassembly and assembly of left front cover Disassemble and assemble the left front cover according to the following diagram. Use the thread retaining adhesive LOCTITE 648 while assembling the pressure plate bolt. Use the thread retaining adhesive LOCTITE 648 while assembling the magneto stator connecting bolt.
Page 78 YG125-30A Maintenance Manual Magneto and starting system Rotor assembly Disk gear Disk gear washer To remove the clutch: Remove the left front cover (See Removal of left front cover). Remove the starting idle gear, double-linked gear, Double-linked Gear Notice: Do not let the semicircular key drop into the crankcase.
Page 79 YG125-30A Maintenance Manual Magneto and starting system Disassembly and assembly of rotor assembly Disassemble and assemble the rotor assembly according to the following diagram. Use thread retaining adhesive LOCTITE 648 on the screw while assembling, with the tightening torque being 10-14N.m...
Page 80 YG125-30A Maintenance Manual Magneto and starting system carefully take it out from the left side. and screw up the nut M12 to the torque of 45N.m Take it out from the left Torque wrench Rotor fastening to Motor connecting bolt...
Page 81 YG125-30A Maintenance Manual Magneto and starting system 1、Check the spline gear of output shaft of the starting motor for defect, squeezing, deforming, etc. 2、Check the idle gear and double-linked gear for missing teeth, etc. To install the double-linked gear cove: ⑴Clean up the left front cover and parts，mount the...
Page 82 YG125-30A Maintenance Manual Magneto and starting system 7、Measure the washer thickness, the maintenance limit: ≥0.4mm Vernier calipers https://www.motomanuals.net/...
Page 83 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism 9、Crankcase, crankshaft and Shift mechanism Right hand crankcase body Gearshift drum Crankshaft Main shaft Counter shaft Left hand crankcase body https://www.motomanuals.net/...
Page 84: Crankcase, Crankshaft And Shift Mechanism
YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Crankcase, crankshaft and Shift mechanism Maintenance notice Crankshaft and balance shaft Troubleshooting Variable transmission system Crankcase Maintenance notice To carry out the maintenance stated herein, the engine must be removed from the frame.
Page 85 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Troubleshooting  Noise from engine Crankshaft bearing worn; Connecting rod big end bearing worn; Driving/driven shaft bearings worn; Balance shaft supplementary tooth spring failure.  Driving/driven shaft gears engaged badly Shift fork bent or damaged;...
Page 86 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Crankcase Notice To remove the crankcase: Do not pry the left/right hand crankcase body by Remove the engine from the frame (engine oil fully inserting such tools as screwdrivers into the mould drained) and put it on the assembly operating table.
Page 87 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Mount other parts and components of engine, mainly include right hand crankcase cover, clutch, gear shifter, cylinder head cover, camshaft, cylinder head, cylinder, piston, left front cover, rotor assembly, electrical starting transmission system, driving drive sprocket, etc.
Page 88 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Removal and installation of crankcase Procedure Quantity Remarks Removing order Installation is in the reverse order of removal Right hand crankcase O-ring engine oil filter net Release oil bolt Left hand crankcase...
Page 89 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Do not remove breather pipe joint, otherwise damage will be caused. Generally, do not remove the bearing; if it is removed, coat engine oil on surfaces of spare parts while pressing it in; mount it with SST and confirm the press-in depth of the bearing.
Page 90 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Disassembling the needle bearing may damage it; in case it is damaged, always change a new one. Replace washer with new ones after being removed. Apply the thread retaining adhesive LOCTITE 648 while assembling the stud bolt.
Page 91 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Remove the (left hand) crankcase (See “Removal of Use a high power electric drier to heat the right left hand crankcase"). crankcase body balance shaft bearing until the Remove the balance shaft.
Page 92 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Knock Procedure Quantity Remarks Removing order Installation is in the reverse order of removal Left hand crankcase Crankshaft Balance shaft Right hand crankcase https://www.motomanuals.net/...
Page 93 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Disassembly and assembly of crankshaft and balance shaft Do not further disassemble the crank shaft, otherwise the spar parts may be damaged. Disassemble and assemble the balance shaft according to the following diagram.
Page 94 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Nut M14*1.25 Apply engine oil while assembling bear clearance, the maintenance limit: ≤0.80mm. Crankshaft and balance shaft inspection Check whether the crankshaft journals are abnormally worn, whether the connecting rod can Clearance gauge rotate flexibly and whether there is significant noise while rotating.
Page 95 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Variable transmission system Assemble the shift fork with To remove the variable transmission system: Mount the gearshift drum.。 Remove the (left hand) crankcase (See “Removal of Change the O-shaped sealing ring, mount the shift left hand crankcase").
Page 96 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Attention: the washer, retainer, etc. must be assembled in place at the correct positions, the spare parts 8 apply lubricating oil. while assembling Procedure Quantity Remarks Sequence of disassembling Assembling reverse order disassembling.
Page 97 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism Removal of left hand crankcase cover(See “Removal and pit corrosion; check whether the shift fork is bent and whether the gearshift drum guiding slot is damaged. of left hand crankcase cover ").
Page 98 YG125-30A Maintenance Manual Crankcase, crankshaft and Shift mechanism 3、Mount the rotor assembly(See “Mount of left hand crankcase cover "). 4、Mount the left hand crankcase cover(See “Mount of right crankcase cover "). Warning Thread retaining adhesive LOCTITE243 must be applied to the rotor retaining nut M12 while assembling, with the tightening torque being 45N.m.
Page 99 YG125-30A Maintenance Manual Frame and exhaust system 10、Frame and exhaust system https://www.motomanuals.net/...
Page 100: Frame And Exhaust System
YG125-30A Maintenance Manual Frame and exhaust system Frame and exhaust system Maintenance notice Removal and installation of rear mudguard Troubleshooting Removal / installation of exhaust muffler Coverings, headlamp and meter Rear position lamp assembly Maintenance notice To carry out the maintenance stated herein, take special care of the scratches and damages to the coverings, meter and light fittings.
Page 101 YG125-30A Maintenance Manual Frame and exhaust system  Side cover and seat Pull off the headlamp patch plug to remove the  Remove the two nut, remove the seat. headlamp.  Pull off the left/ right turn lamp connecting wire from the headlamp bracket.
Page 102 YG125-30A Maintenance Manual Frame and exhaust system Headlamp dimming Replacement of turn lamp bulb  Before driving, check the brightness, direction, etc. of the Loosen the screws, remove the lamp lampshade  headlamp. Lightly press bulb, rotate in counter-clockwise. ...
Page 103 YG125-30A Maintenance Manual Frame and exhaust system  Dismantle the suspension bolt on the muffler, check whether it is sliding. Connecting bolt  Dismantle muffler connecting nut, check whether the nut and bolt is sliding.  Dismantle the muffler, check whether the washer is damaged.
Page 104 YG125-30A Maintenance Manual Front wheel, front overhang and steering stem 11、Front wheel, front suspension device and steering stem https://www.motomanuals.net/...
Page 105 YG125-30A Maintenance Manual Front wheel, front overhang and steering stem Front wheel, front suspension device and steering stem Maintenance notice Front suspension device Troubleshooting Front brake Control subassembly Steering stem Front wheel Maintenance notice This section introduces the removal, installation and maintenance of the front wheel, front suspension device (front fork), front brake and steering stem.
Page 106: Front Wheel, Front Overhang And Steering Stem
YG125-30A Maintenance Manual Front wheel, front overhang and steering stem Tire pressure insufficient Shift fork bent or damaged.  Insufficient suspension device rigidity Insufficient front fork spring Insufficient hydraulic oil refilled in the front fork  Poor brake performance The brake is not adjusted as per regulations...
Page 107 YG125-30A Maintenance Manual Front wheel, front overhang and steering stem 2mm) Gear is damaged． Speedometer Replace The indicator of the speedometer gear The gear drive speedometer fails to move gear box ring is damaged． Maintenance of Front Shock Absorber Component...
Page 108 YG125-30A Maintenance Manual Front wheel, front overhang and steering stem For the damage form, fault symptom and repair method of front brake Item Damage form Trouble symptom of Trouble symptom of Repair method component motorcycle brake 1iquid is brake liquid is...
Page 109 YG125-30A Maintenance Manual Front wheel, front suspension device and steering stem  Remove the right brake cylinder body. Control subassembly Remove the right brake cylinder body 1、Remove the left/right balance weight.  Remove the clutch control line and disassemble the 2、Remove the right handle and right combination switch...
Page 110 YG125-30A Maintenance Manual Front wheel, front suspension device and steering stem  Remove the clip and take out the grip tube Maintenance of wheel To remove the front wheel Support the motorcycle with a jack to lift the front wheel Bolt.
Page 111 YG125-30A Maintenance Manual Front wheel, front suspension device and steering stem Disassembly and assembly of front wheel Disassemble and assemble the front wheel according to the following diagam. After the bearing is removed, replace with a new bearing along with dust seal.
Page 112 YG125-30A Maintenance Manual Front wheel, front suspension device and steering stem Unscrew the upper / lower connection plate bolt and. the Check Dismantle oil drain bolt and check bolt whether or direction of the tube bolt not is loose. Pull off the front damper Drain off absorber oil and check quality whether or not is turned.
Page 113 YG125-30A Maintenance Manual Front wheel, front suspension device and steering stem Dismantle circlip and return spring to check whether 10) Fill absorber oil per standard. or not there are elasticity Oiling quantity of one front absorber: 440 ± 2ml/(cafe racer); 220ml(scrambler), the brand is CN1# shock...
Page 114 YG125-30A Maintenance Manual Front wheel, front suspension device and steering stem To mount of steering stem Removal of steering stem Installation is in the reverse order of removal Steering stem While installing the steering stem, adjust the adjusting nut Park the motorcycle on the plane ground, and...
Page 115 YG125-30A Maintenance Manual Front wheel, front suspension device and steering stem Warning: When it is replaced with a new brake strip or brake disc, do not drive it immediately; instead, drive it after holding and releasing the front brake handle until the brake strip and the brake disc are well engaged.
Page 116 YG125-30A Maintenance Manual Front wheel, front suspension device and steering stem https://www.motomanuals.net/...
Page 117 YG125-30A Maintenance Manual Rear wheel and rear suspension device 12、Rear wheel and rear suspension device https://www.motomanuals.net/...
Page 118 YG125-30A Maintenance Manual Rear wheel and rear suspension device 12、Rear wheel and rear suspension device Maintenance notice Rear fork Troubleshooting Rear shock absorber Rear wheel Maintenance notice This section introduces the removal, installation and maintenance of the rear wheel, rear brake, rear fork and rear damper .While repairing the rear wheel and rear damper, reliably stand the motorcycle from under the engine a jack or...
Page 119 YG125-30A Maintenance Manual Rear wheel and rear suspension device For the damage form, fault symptom and repair method of rear wheels Component Damage form Trouble symptom of Trouble symptom of Repair method description component motorcycle Rear rim is twisted Rear rim is twisted and Off racking in running．rear...
Page 120 YG125-30A Maintenance Manual Rear wheel and rear suspension device Rear wheel tightening torque of 60-90N.m Warning To remove the rear wheel The rear wheel spindle must be firmly screwed 1) Stand the motorcycle with a jack to lift the rear wheel up to the required torque of 60-70N.m...
Page 121 YG125-30A Maintenance Manual Rear wheel and rear suspension device 3、Remove the rear damper and rear fork connecting bolt. Take out bush and dismantle bolt of rear driven chain Bolt disc. Normal tooth shape Check rear driven chain disc whether it is exceed limit 4、Take out the rear fork backwards.
Page 122 YG125-30A Maintenance Manual Rear wheel and rear suspension device Rear Brake Rear fork bearing inspection Pulling the front & rear brake, checking the wear and tear Replace the removed seal ring and needle bearing with of the brake shoe. If the mark "△" on the drum brake new ones.
Page 123: Chapter 4 Electrical System
The development of electronics will especially influence the motorcycle’s electrical system significantly. YG125-30A’s electrical system uses a lot of advanced vehicle electronics technologies that are much more complicated then the traditional motorcycle. It comprises the following sub-systems: •...
Page 124 Power supply system is the precondition for a complete vehicle to operate, capable of providing sufficient electric energy for other electrical systems. The main contents include recharging, charge storing and discharging. YG125-30A power supply features large power supply capacity as high as more than 250W. It comprises the following parts and components: •...
Page 125 YG125-30A Maintenance Manual Power supply system Maintenance of Charging System Check plate electrode whether is damaged Disassemble. assemble and check charging system Check socket whether contact well. Socket check connector socket of rectifier and measure Dismantle rectifier bolt and measure two yellow output voltage by multimeter to (13.0-13.3)v...
Page 126 YG125-30A Maintenance Manual Power supply system Major faults diagnosis Phenomenon Possible causes Solutions    No electricity in the complete Main fuse is blown; Replace main fuse   vehicle: Main fuse circuits contact poorly; Re-plug.   Accumulator’s positive and ...
Page 127: Starting System
When the engine starts to work, an exogenous action is needed to help it run, thus entering the ignition & fuel supply procedure to enable the internal combustion engine to combust repeatedly and work steadily. YG125-30A motorcycle is only equipped with electric controlled starting. First, release it from the protection of shift position switch, side stand switch and clutch switch;...
Page 128 YG125-30A Maintenance Manual Starting system Maintenance of starting system Disassemble, assemble and maintain Check positive and negative pole of battery Turn on ignition switch and flameout switch to whether contact well check electrical start whether energize. Battery Check relay whether is damaged...
Page 129 YG125-30A Maintenance Manual Starting system 12. Check switch plug of relay whether is loose. 13. Check clutch electrical starting switch plug whether is damaged or loose. Major faults diagnosis Phenomenon Possible causes Solutions    Starting relay Accumulator voltage too low;...
Page 130 YG125-30A Maintenance Manual Illumination signal system 16、Illumination signal system Overview Major parts and components Circuit schematic drawing Major faults diagnosis Overview Illumination signal system is an important guaranty for the safe driving of the vehicle. It includes the headlamp illumination system, signal lamp control system and horn system.
Page 131 YG125-30A Maintenance Manual Illumination signal system Circuit schematic drawing https://www.motomanuals.net/...
Page 132 YG125-30A Maintenance Manual Illumination signal system Take off headlamp switch socket to check whether Maintenance of illumination system there is current Turn on ignition switch and flameout switch to check electrical start whether energize. Dismantle headlamp bolt to check lamp case whether is damaged.
Page 133 YG125-30A Maintenance Manual Illumination signal system 13. Check tail lamp and brake lamp socket whether lose 18. Check neutral socket whether contact well. contact or bulb is burned 19. Signal lamp control systems 14. Take off ignition switch socket to check whether Check flasher whether is burned or plug is loose.
Page 134 YG125-30A Maintenance Manual Illumination signal system Major parts and components Right combination switch Head lamp Fuel level sensor Combined rear position lamp Horn Front brake lamp switch Rear brake lamp switch Left combination switch https://www.motomanuals.net/...
Page 135: Illumination Signal System
YG125-30A Maintenance Manual Illumination signal system Major faults diagnosis Phenomenon Possible causes Solutions    Headlamp does not Accumulator voltage too low; Recharge the accumulator;   illuminate; Corresponding fuse is not connected or is Connect the fuse or replace it;...
Page 136: Electrical Starting Control System
The information display system displays the dynamic and static information of the complete vehicle on the instrument panel for the driver’s safe operation. The complete vehicle information the YG125-30A displays include: vehicle speed, engine speed, fuel indicator, Neutral indicator, turn indication, high-beam indication, total / subtotal mileage traveled and EFI Indicator.
Page 137 YG125-30A Maintenance Manual Electrical starting control system Major parts and components ○ Combination meter Outline drawing Line color function corresponding table COLOUR FUNCTION COLOUR FUNCTION Black Power Supply(+) Green/ Red Neutral indicator The rotational speed signal green Power Supply(-) Black/ Yellow...
Page 138 YG125-30A Maintenance Manual Electrical starting control system Maintenance of electrical starting control system Turn on ignition switch and flameout switch to check electrical start whether energize. Check fuse whether is burned. Fuse whether Dismantle headlamp holder to check holder whether there is current.
Page 139 YG125-30A Maintenance Manual Electrical starting control system Major faults diagnosis Phenomenon Possible causes Solutions    Winker indicator is out of The winker indicator filament is burnt Replace winker indicator bulb work    Meter dial illuminator is out...
Page 140 YG125-30A Maintenance Manual Engine management system 18、 Engine management system System Overview Tools Major parts and components Maintenance depending on the malfcode Maintenance depending on the performance Circuit schematic drawing Maintenance of Engine management system System Overview Components of system and Operating principle...
Page 141: Engine Management System
YG125-30A Maintenance Manual Engine management system Major parts and components Fuel Injector Throttle body Cylinder Head Temperature Sensor Idle speed control valve Intake air pressure sensor Throttle sensor Electronic control unit( ECU) Oxygen sensor https://www.motomanuals.net/...
Page 142 YG125-30A Maintenance Manual Engine management system Circuit schematic drawing https://www.motomanuals.net/...
Page 143 YG125-30A Maintenance Manual Engine management system ITEM PIN No. DESCRIBE ITEM PIN No. DESCRIBE J1-1 IACAHi J2-1 COILA J1-2 MAGNETO CUT RELAY J2-2 J1-3 J2-3 KW2000 J1-4 J2-4 CRANK HI J1-5 J2-5 INJA J1-6 TACH J2-6 J1-7 CANLo J2-7 O2AHTR...
Page 144 YG125-30A Maintenance Manual Engine management system Maintenance depending on the malfcode. Description If the issure cannot repeat, the issure analysis may be wrong. The multimeter below means the digital type. Pointer-type is forbidden. If the malfcode shows the voltage is low, it means maybe the wire is short to ground. If the malfcode shows the voltage is high, it means maybe the wire is short to battery.
Page 145 YG125-30A Maintenance Manual Engine management system Malfcode：P0107 Information：MAP Circuit Low Voltage or Open ITEM OPERATION RESULT NEXT STEP Connect the diagnostic tool, and ignition on. Next Check the data of ‘BARO’. Make sure whether it is about 100kPa Step 5...
Page 146 YG125-30A Maintenance Manual Engine management system Malfcode：P0113 Information：IAT Circuit High Voltage ITEM OPERATION RESULT NEXT STEP Connect the diagnostic tool, and ignition on. Next check whether the data of ‘intake air temperature’ equals to the real intake Setp 5 air temperature.
Page 147 YG125-30A Maintenance Manual Engine management system Malfcode：P0122 Information：TPS Circuit Low Voltage or Open ITEM OPERATION RESULT NEXT STEP Connect the diagnostic tool, and ignition on. Next Step 5 Check whether the data of ‘Throttle opening’ is bettwen 0%-1%. Next Open the throttle to 100% slowly, check whether the data of ‘throttle Step 5 opening’...
Page 148 YG125-30A Maintenance Manual Engine management system Malfcode：P0201 Information：Injector 1 Circuit Malfunction ITEM OPERATION RESULT NEXT STEP Connect the diagnostic tool, and ignition on. Next Remove the conneter of injecor 1, use multimeter to check whether the Step 4 voltage of Pin A is about 12V.
Page 149 YG125-30A Maintenance Manual Engine management system Maintenance depending on the performance. Before issue analysis, please check: The MIL works well. Clear the history malfcode. When the malfcode comes again, note the condictions. Check the appearance Whether there is leakage of the fuel pipe or not.
Page 150 YG125-30A Maintenance Manual Engine management system Next Check wether the fuel pump pressure is about 250kPa at idle. Check the pump. Next Pull out the spark plug, check whether the sparkover is normal. Check the ignition system Check the engine...
Page 151 YG125-30A Maintenance Manual Engine management system engine works well Change the sensor Check whether the air filter is blocked and whether the intake Intake system maintenance pipe leaks. Next Next Check whethe the fuel pressure is about 250kPa. Check the pump...
Page 152: Electrical System Diagram
YG125-30A Maintenance Manual Electrical System Diagram 19、Electrical System Diagram https://www.motomanuals.net/...
Page 153 Mar. 2017 The copyright is owned by the company ; and shall not be copied or reproduced without permission Chongqing YINGANG technology group co., LTD Address: No. 71 tongxing nan road, beibei district, chongqing, China Tel: 400-809-6638 URL: http://www.cqyingang.com...

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