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LONCIN YF300, Manual, Page: 36 / 53

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LONCIN YF300 Manual Download Page 36

36 

Check flatness of driven plate by 
thickness gauge 
Standard

：

       

≤0.1 

Limit

：

0.2 

 
 
 
 
 

Check spring length under free condition 
by vernier caliper 
Standard

：

          35.5 

Limit

：

  34 

 
 
 
 
 
 

Install clutch and driving gear 

 

Install woodruff key 
Install driving gear 
Install flat washer and shaft sleeve 
of clutch 

 
 
 
 
 
 

Install outer case of clutch 
Install washer of lower surface 
of clutch center case 

 
 
 
 
 

Install center case comp. 
Install washer of locking nut of clutch 
Install locking nut of clutch 
Installation torque

：（

70

～

80

）

N·m 

 
 
 
 
 
 

Washer 

of 

locking nut 

Center case 

Summary of Contents for YF300

Page 1: ...made this maintenance manual for more convenience and better guidance for users and maintainers of Loncin All the data diagrams informations performance targets are the latest when the manual is printing Loncin motor co ltd reserves the right of revising the manual at any time without notification in advance All rights reserved by Loncin motor co ltd for any parts of this manual and no reprint is ...

Page 2: ...adjustment 10 4 Fuel system 13 5 Cooling system 16 6 Cylinder and air valves 18 7 Cylinder body and piston 28 8 Clutch component 33 9 Gearshift system 38 10 Magneto and electrical starting component 40 11 Crankshaft and transmission system 44 12 Fault diagnosis 50 ...

Page 3: ...oncin specification and requirement the motorcycle may damage 2 Washer seal parts and split pin need to be replaced when re intallation after disassembly is needed 3 Bolts and nuts should be fastened by the sequence of diagonal cross and reached stipulated torque by turning 2 3 times 4 Flammable cleaning fluid for parts washing is not allowed Spread lubricant on movable surface of parts before ins...

Page 4: ...ke OHV Ignition CDI Lubrication Pressure and splash Cooling Water Transmission device Type of clutch Manual operation clutch wet and plates Gearshift International gearshift Primary ratio 2 864 1st gear 3 2nd gear 2 3rd gear 1 5 4th gear 1 25 5th gear 1 05 6th gear 0 905 Starting Foot and electrical Carburetor Vacuum and diaphragm MV34 5A Ignition advance angle curve or working set point 1700 200r...

Page 5: ...nut of clutch M12 70 80 11 Locking nut of impeller M6 10 15 12 Controller valve comp of oil M12 10 15 13 Fastening bolt of guiding plate of ratchet M6 8 12 14 Fastening bolt of rotor of magnetor M12 100 120 15 Fastening bolt of gearshift drum plate M6 10 15 16 Bolt of check plate M6 10 15 17 Positioning bolt of gearshift arm M10 25 30 18 Oil drainage plug M12 32 40 19 Pin axis of chain adjustor M8...

Page 6: ...ge Carburetor inspection adjustment Spark plug cap Cleaning Each 4000km Oil filter Replacement Oil replacement Sprocket wheel checking Coolant replacement Each 2 years Heat radiator checking Fuel system cleaning Bolt nut washer checking Lubricant system checking Maintenance of motorcycle should be conducted according to chart above Items in chart above should be done by Loncin service maintainer i...

Page 7: ...mption B Dirt lubricant 1 Oil leakage of engine 1 Replace oil without following chart above 2 Abrasion of piston ring 2 Thread damage of oil filling port 3 Abrasion of guiding rod of air intake and exhaust valve 4 Abrasion or damage of oil drip pan C Abnormality of lubricant 1 Low level of oil 2 Blocked oil passage or filtering screen 3 Oil pump damage Lubrication system of engine Lubricant is imp...

Page 8: ...lete oil drainage in crankcase could be ensured Lay one oil plate under engine and screw off bolt A for releasing oil Check seal washer and replace if damage is found Screw up bolt A and washer when old lubricant completely released Fastening torque 18N m Fill new oil and check its level Requirement for newly added oil Fill oil by 1 5L when new engine left factory Fill oil by 1 3L when oil need re...

Page 9: ...e washer C and elastic washer B and then remove axis of oil pump Screw off screw E of oil pump cover and remove cover A Remove rotors of inner and outer Inspection of oil pump Open oil pump and then check pump body A outer rotor B inner rotor C and cover D change each damaged part or complete oil pump in case any damage is found Washing of oil screen Remove right crankcase and take out oil screen ...

Page 10: ...plug B8RC Clearance of spark plug 0 6 0 7 Clearance of valves Air intake valve 0 1 0 19 Air exhaust valve 0 15 0 24 Lead angle for ignition 1700 200r min when 0 1 5000 200r min when 25 1 Rotation speed in idling 1500 150r min Pressure of cylinder 1200kPa Spark plug Remove spark plug by its sleeve and visually check damages on insulator of spark plug and also check ablation on electrode and replace...

Page 11: ...uld be parallel with joint surface on cylinder head Note Air intake cam corresponds scale line of IN while air exhaust cam of EX Checking of valve clearance Insert feeler gauge between camshaft and tappet rod for checking valve Clearance Clearance of air intake valve 0 1 0 19 Clearance of air exhaust valve 0 15 0 24 Adjustment is needed when clearance is incorrect Adjustment of valve clearance Rem...

Page 12: ...1500 150r min Adjustment screw of idling speed Pressure test of cylinder Start engine for pre heating and then turn off engine and remove spark plug and install pressure tube B on installation position of spark plug and then install pressure meter A on pressure tube B completely turn on choke and throttle and finally turn on starting motor for 4 6 times Note Check air leakage on each joint of pres...

Page 13: ...gasoline in float chamber Troubleshooting A Engine could be ignited but unable to start C High concentration of mixing gas 1 No fuel in fuel tank 1 Too high the fuel level in caburetor 2 No fuel entered carburetor 2 Air nozzle of carburetor blocked 3 Too much fuel in cylinder 3 Float seized ot float needle failure 4 Air filter blocked 4 Dirty air cleaner B Low concentration of mixing gas D Unstabl...

Page 14: ...of float arm Remove float and its needle Check abrasion or damage on contact surface of float needle Replace float needle in case it is necessary Remove main jet foam tube main nozzle and idling jet Caution Keep in mind installation position of screw and its turning times or trouble will be met in re assembly Wash surface of carburetor its holes and passage by cleaning fluid and then clean up dirt...

Page 15: ...d needle of float and float height could be also adjusted on height gauge Installation of carburetor After carburetor installed adjust the free moving distance of throttle lever by adjustment device on throttle cable Free moving distance of throttle lever 2 3mm Adjustment for idling speed Start engine and raise its temperature to working condition and adjust throttle screw for raising idling speed...

Page 16: ...t allowed due to water has cooling function only without functions of antiscale antifust and raising boiling point in this case engine usually uses running and hard water easily lead to rustiness on water pump shaft scaling and bad heat radiation of water passage and overheating of engine Check coolant in water tank when engine is cold in case much reduction is found it indicates there is coolant ...

Page 17: ...nd water rotating ring In case damage is found replacement is needed Check damage on end surface of cooling pump cover In case damage is found replacement is needed Installation of cooling pump Press and install static water seal ring on right cover Press and install water rotating ring on impeller of water pump whose surface matches static ring faces outwards Tightly lock impeller of cooling pump...

Page 18: ... Height of air exhaust cam 36 17 36 27 36 07 Diameter of camshaft 22 967 22 980 22 94 Diameter of hole of camshaft bracket 23 000 23 021 23 08 Clearance between camshaft and bracket 0 020 0 054 0 15 Valves Width of line of air intake valve 0 7 0 45 Width of line of air exhaust valve 0 8 0 5 Diameter of rod of air intake valve 4 475 4 49 4 460 Diameter of rod of air exhaust valve 4 455 4 470 4 440 ...

Page 19: ...g 2 Cylinder head Noisy Poor connection between cylinder head and spark plug 1 Incorrect valve adjustment Damage of leakage on cylinder head gasket 2 Valve seized up or spring crack Crack or sand hole on cylinder head 3 Camshaft worn out 3 Cylinder body piston 4 Long timing chain Wide clearance between piston rings or crack 5 Wrong timing of gas distribution Pistion with crack or damage 6 Abrasion...

Page 20: ...m bracket Remove cylinder head cover Remove bolt connects bracket Remove cam bracket Removal of camshaft Remove cylinder head cover Remove tensioner comp on cylinder head and bolt on cylinder body Remove bolt connects bracket Remove cam bracket Remove chain Remove camshaft Note No timing chain drop into crankcase is allowed ...

Page 21: ...ticlockwise and aline timing mark A on left front cover and mark B T shaped scale line on magnetor through viewing C on left front cover and now the piston is at upper stopping point of compression stroke Timing scale line should be parallel with joint surface of cylinder head when installing camshaft Note Air intake cam corresponds scale line of IN while air exhaust cam of EX Spread lubricant on ...

Page 22: ...475 4 49 4 460 Exhaust valve 4 455 4 470 4 440 Insert each valve into guiding tube and observe its movement Measure inner diameter of each guiding tube of valve by internal micrometer and finally calculate clearance between tappet rod and guiding tube Standard Limit Guiding tube of intake valve 4 510 4 522 4 59 Guiding tube of exhaust valve 4 510 4 522 4 59 Clearance between intake valve and its g...

Page 23: ... Inner spring 36 2 34 5 Outer spring 41 1 39 4 Replace guiding tube Fix cylinder head and remove guiding tube from valve hole outwards by puller Caution No damage to cylinder head is allowed when disassembling guiding tube of valve Press and install new guiding tube and o ring on cylinder head and make expansion for new guiding tube Caution Spread cutting oil on reamer A when hole expansion is con...

Page 24: ... door line of seat ring is unqualified repair seat ring until it meets the demand for correct sealing Check valve Remove valve and check its contact surface In case coarse uneven abrasion of contact surface of valve is found or contact to valve seat is abnormal replacement for valve is needed Repair valve seat Milling cutter of valve seat Milling cutter with three different angle Mill upper ring b...

Page 25: ...een valve and its seat is important for sealing performance of engine In case too high the contact surface decrease its height by milling cutter of 32 In case too low the contact surface rise its height by milling cutter of 60 Finally mill by milling cutter of 45 until the width of contact surface of valve seat reached stipulated data After valve seat finished machining spread abradant on valve se...

Page 26: ...ion for cylinder head Clean up plane of cylinder after cylinder gasket Removed and then install new gasket and positioning pin Caution No dust or impurity enter into cylinder is allowed 1 Install new gasket and locating pin 2 Install bolt A B and washer on cylinder head 3 Install bolts connect cylinder body 4 Install adjustment washer and tappet rod of valve 5 Install camshaft 6 Install positionin...

Page 27: ...ead Screw up fastening bolts on cylinder head cover Fastening torque for bolts should be 8 10 N m Note When seal ring of fastening bolt for cylinder head cover is in installing the side of seal ring with metal lining faces upwards This side matches flange face of bolt on cylinder head cover ...

Page 28: ... 008 17 04 Width of groove of 1st ring 1 01 1 03 1 11 Width of groove of 2nd ring 1 01 1 03 1 11 Width of groove of 3rd ring 2 01 2 03 2 11 Connective rod Hole diameter of small end 17 013 17 025 17 05 Piston pin Outer diameter 16 994 0 17 000 16 96 Clearance between piston and cylinder 0 03 0 06 0 12 Clearance btween piston pin and its hole 0 002 0 014 0 02 Clearance between piston pin and small ...

Page 29: ...ylinder head Refer to section 6th Remove gasket and positioning pin Remove cylinder body Caution No timing chain drop into crankcase is allowed Clean up remains on cylinder surface by scraper Caution Immerse into gasoline may lead to easy work while avoiding damage on contact surface of cylinder Check cylinder Check abrasion and damage on cylinder Measure inner diameter in three positions which ar...

Page 30: ...rings and their grooves by thickness gauge A Standard data 1st ring 0 02 0 06 2nd ring 0 02 0 06 Limit data 1st 2nd ring 0 16 Remove piston ring Caution No damage to piston rings during disassembling is allowed Insert each piston ring into cylinder and measure clearance Standard data 1st ring 0 15 0 3 2nd ring 0 20 0 35 Limit data in maintenance 1st ring 0 65 2nd ring 0 7 Check abrasion or damage ...

Page 31: ...ngs Caution No damage on piston and its rings during installation is allowed The side with mark of rings face upwards Flexible turning of piston ring is needed after installed No opposite installation for top and 2nd ring is allowed Issues need pay attention during installaion Opening on 1st ring face to direction of exhaust Opening on 2nd ring and oil ring face to air intake Interval between open...

Page 32: ...rlace opening on piston New circlip must be used when in re installation No circlip drop into crankcase is allowed Install cylinder body Install new gasket and positioning pin Spread oil on cylinder and piston rings Install cylinder Caution No damage to piston During installation is allowed No timing chain drop into crankcase is allowed Install gasket and positioning pin Install cylinder head ...

Page 33: ...fter right crankcase cover removed without taking down engine from motorcycle No damage to right crankcase cover and joint surface of crankcase is allowed no impurity enter engine is allowed Specification of each part Items Standard mm Limit mm Clutch Free moving distance 2 3 Thickness of driving plate 2 95 3 05 2 7 Thickness of driven plate Max flatness0 1 0 2 Length of spring under free conditon...

Page 34: ... needed Install clutch cover Install positioning pin for clutch cover Turn downwards the operation rod Replace new gasket for clutch cover Install clutch cover Fasten installation screw Fastening torque 8 10 N m Remove right crankcase cover Drain off oil Drain off coolant Remove water pipe Remove clutch cover Remove cover of water pump Remove impeller of water pump Loosen connective bolts of right...

Page 35: ...at washer on clutch Remove primary driving gear Remove semi round key Disassemble clutch Loosen spring bolt Remove lifting plate spring and center case Remove driving plate with friction material and driven plate steel plate Check clutch Check thickness of driving plate by vernier caliper Standard 2 92 3 08 Limit 2 7 Pushing rod Pushing plate Locking nut Bolt Spring Center case Lifting plate ...

Page 36: ...nstall clutch and driving gear Install woodruff key Install driving gear Install flat washer and shaft sleeve of clutch Install outer case of clutch Install washer of lower surface of clutch center case Install center case comp Install washer of locking nut of clutch Install locking nut of clutch Installation torque 70 80 N m Washer of locking nut Center case ...

Page 37: ...and driving gear when installing washer of locking nut of driving gear and clutch Install right crankcase cover Install positioning pin and new gasket Install right crankcase cover Install fastening screw screw up bolt at hole of positioning pin Torque of installation 8 12 N m Install clutch cover Install secondary filter and its cover Install impeller of water pump Install cover of water pump ...

Page 38: ...ift device no impurity drop into engine is allowed Remove cover of gearshift device Remove gear indicator comp Remove installation bolt B of gearshift cover Remove cover of gearshift device Remove gearshift spindle Remove installation screw of touching plate of gear indicator Remove touching plate of gear indicator Remove gearshift spindle comp Loosen installation screw of check plate Remove check...

Page 39: ...all check plate Install positioning pin of gearshift drum plate Install gearshift drum plate Install touching plate Install screw of touching plate Screw fastening torque 8 12 N m Install check plate comp Install bolt of check plate Installation torque of bolt of check plate 8 12 N m Install gearshift arm Install positioning bolt F of gearshift arm Installation torque of positioning bolt 25 30 N m...

Page 40: ... front cover Install left front cover Remove magneto Install magneto Remove electrical starting gear Notice in maintenance This section introduce removal and installation of magneto the work could be done without removing engine only need remove left front cover Remove starting motor Remove installation bolt A of starting motor Remove starting motor B ...

Page 41: ...tion bolt A of stator Remove installation screw C of wire pressing plate of stator Remove stator B of magneto Remove washer and installation bolt of rotor Remove rotor comp of magneto Remove electrical starting gear Remove plate shaped gear A and collar below it Remove small double gear and flat washer Remove installation bolt of gear chamber cover on left front cover Remove cover of gear chamber ...

Page 42: ...ped gear Install plate shaped gear Install small double gear and flat washer Install magneto Install rotor comp of magneto Install fastening bolt of rotor Bolt fastening torque 100 120 N m Install stator comp B of magneto Install fastening bolt A of stator Fastening torque 5 7 N m Install wire pressing plate of stator Fasten bolt of wire pressing plate Fastening torque 8 12 N m ...

Page 43: ... N m Install starting motor Install starting motor into left cover Fasten installation bolt of starting motor Fastening torque 8 12 N m Install big double gear and flat washer 1 pcs each at upper and lower position of gear chamber cover on left front cover Install new gasket of gear chamber cover Install gear chamber cover Fasten bolt of gear chamber cover Fastening torque 8 12 N m ...

Page 44: ...kcase cover Remove clutch comp Remove oil pump comp Remove starting spindle comp Remove left front cover Remove magneto comp Remove electrical starting gear and starting motor Remove cover of gearshift device Remove gearshift arm comp Remove check plate comp and gearshift drum plate Remove cylinder head comp Remove cylinder body comp Remove piston comp Remove chain chain adjustor and tension plate...

Page 45: ...ring Breaking down crankcase Remove sleeve A and o ring B of countershaft Loosen bolt connects crankcase Remove right crankcase body Remove positioning pin of case body Clean up seal glue on end face and no damage on end face of case body is allowed Caution Break apart left and right crankcase by knocking by a soft hammer left and right by turns no prying by screw driver is allowed Remove transmis...

Page 46: ...t Measure total clearance B between end face of bigger end of connecting rod and crankshaft by thickness gauge A Standard 0 2 0 4 Limit 0 6 Turn the crankshaft by hand and inspect its radial bounce by dial gauge Standard 0 03 Limit 0 05 In case damage or abrasion is found on bearing of crankshaft replacement is needed ...

Page 47: ...eck abrasion or damage on each gear of main and counter shaft Check width B of fork groove Standard 5 0 5 18 Limit 5 33 Check thickness A of fork and its plate Standard 4 93 5 0 Limit 4 83 Check diameter A of fork pin Standard 5 9 5 95 Limit 5 8 Check groove width B for fork on gearshift drum Standard 6 05 6 15 Limit 6 2 ...

Page 48: ...nkcase together Install gearshift drum Install forks and insert forks into main and counter shaft and put fork pin into line shaped groove of gearshift drum Pay attention to mark on forks and no wrong installation is allowed Aline holes on each fork and insert axle of forks through the holes Turn and check flexibility of main and counter shaft in case poor flexibility is found re installation and ...

Page 49: ...hain chain adjustment plate and chain tensioning plate Install piston comp Install cylinder body comp Install cylinder head comp Install check plate comp and five star shaped plate Install gearshift arm comp Install cover of gearshift device Install electrical starting gear and starting motor Install magneto comp Install left front cover Install starting spindle comp Install oil pump comp Install ...

Page 50: ...e 8 Break or short circuit of power source 3 Check cylinder pressure Low pressure 1 Starting device skidding and engine starting failure Normal pressure 2 Narrow valve clearance or no clearance 3 Distortion of guiding rod of valve 4 Poor matching between cylinder seat and valve 5 Abrasion on cylinder and piston ring 6 Poor sealing performance of gasket of cylinder head 7 Incorrect installation 8 W...

Page 51: ...or Carburetor blocked 1 Dirty fuel Carburetor without blocking 2 Carburetor without periodic washing 7 Check spark plug Carbon buildup and incorrect color 1 No periodic maintenance was made Normal spark plug 2 Incorrect heat value of spark plug 3 Too narrow the clearance between spark plug and electrode 8 Check oil through view windown Incorrect oil Quantity 1 Too high the oil level Normal oil qua...

Page 52: ...nce when engine under high speed Diagnosis Cause 1 Check valve clearance and ignition timing Incorrect 1 Magneto failure Correct 2 CDI failure 3 Sensor failure 4 Incorrect valve clearance 2 Open fuel tube of carburetor Fuel flow was limited 1 Fuel in fuel tank used up Fuel smoothly flow out 2 Ventilation hole on fuel tank cap blocked 3 Fuel tube from fuel tank to carburetor blocked 4 Fuel switch b...

Page 53: ...ston and cylinder body 2 Abrasion on piston pin and smaller end of crankshaft connecting rod 3 Abrasion on bigger end of crankshaft connecting rod 3 Abnormal noise of bearing 1 Bearing on crankshaft connecting rod damaged 2 Bearing of camshaft damaged 4 Abnormal noise of chain of cam 1 Lengthened chain 2 Teeth abrasion of timing sprocket wheel 3 Abrasion on guiding plate or tension plate 4 Incorre...

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