1992-2000 Yamaha Timberwolf (YFB250) ATV OEM Service & Repair Manual

.YAMAHA YFB250

YAMAHA ,. LlT-11616-08-17

YF8250(D) '92 SERVICE MANUAL © 1991 by Yamaha Motor Co., Ltd. 1st Edition, September 1991 All rights reserved. Any reprinting or unauthorized use without the written permission of Yamaha Motor Co., Ltd. is expressly prohibited.

NOTICE This manual was written by the Yamaha Motor Company, Ltd. primarily for use by Yamaha dealers and qualified mechanics. It is not possible to put an entire mechanic's education into one manual, so persons using this book to perform maintenance and repairs on Yamaha machines should have a basic understanding of the machanical concepts and procedures inherent in machine repair technology. Without such knowledge, attempted repairs or service to the machine may render it unfit to use and/or unsafe. Yamaha Motor Company, Ltd. is continually striving to improve all models manufactured by Yamaha. Modifications and significant changes in specifications or procedures will be forwarded to all Authorized Yamaha dealers and will, where applicable, appear in future editions of this manual. PARTICULARLY IMPORTANT INFORMATION This material is distinguished by the following notation. A WARNING NOTE: The Safety Alert Symbol means ATTENTION! BECOME ALERT! YOUR SAFETY IS INVOLVED! Failure to follow WARNING instructions could result in severe injury or death to the machine operator, a bystander, or a person inspecting or repairing the machine. A CAUTION indecates special precautions that must be taken to avoid damage to the machine. A NOTE provides key information to make procedures easier or clearer.

HOW TO USE THIS MANUAL CONSTRUCTION OF THIS MANUAL Tris manual consists of chapters for the main categories of subjects. (See "Illustrated symbols") This is a chapter with its symbol on the upper right of each page. 1 st title CD : 2nd title ® : This title appears on the upper of each page on the left of the chapter symbol. (For the chapter "Periodic inspection and adjustment" the 3rd title appears.) 3rd title ® : This is a final title. MANUAL FORMAT All of the procedures in this manual are organized in a sequential, step-by-step format. The information has been compiled to provide the mechanic with an easy to read, handy reference that contains comprehensive explanations of all disassembly, repair, assembly, and inspections. A set of particularly important procedure @ is placed between a line of asterisks" *" with each procedure preceded by " • ". IMPORTANT FEATURES • Data and a special tool are framed in a box preceded by a relevant symbol @ . • An encircled numeral ® indicates a part name, and an encircled alphabetical letter data or an alignl11ent mark (j) , the others being indicated by an alphabetical letter in a box ® . • A condition of a faulty component will precede an arrow symbol and the course of action re- ql,Jired the l>ymbol ®. EXPLODED DIAGRAM Each chqpter provides exploded diagrams before each disassembly section for ease in identifying correct disassembly and assembly procedures. 3 2.Rllmov,," ·c ....... '''.11 ill Use,hec.llnkcl,"nplrll"nlllOOI (J) 1i1 C'~:~~~;:.'."111tf tool: n--::=:::;;::;;;:==, IN'SPECTION AND REPAIR CYLIHI)ER HEAD 1, E~ ... " •• te ·C.tbo"dllPOI,ts U ••• ,oun.s.d.o::',~, H07l:, ..... :--- ...... :---.--- TlkeCII,"toIlVo.dlldlmagongthelptrkp1ue '----________ --' ~~::::C'~I:h~:;t~::lu .... ~h:.: ,nWUIO\eIl' Warpfl ...... H"'._t.net , ...... ,.e •. -"".t.,: •• U.ch." .... ' .. <D...ct.thod' ... · )----H~--A~~~~ .:':'=t~.:;~:;:.~nHtlwld ."th.w.'~i.OulOI."."ifiulion.'.· .",'.~. t"- "ybtld., h.ad • PI.~ •• 400 - eoo 'fit w., lind""", on ~ :::'::~:,:~:;;':::':':::::.:~'''''' J :::; lh. Iwlld ....... " I"'", to .... oid •• • I moving 100 m""h mat.,"1 from _ 'idil. ., "" ... """"""""'''"'''' .. ,, FRONT FOR. ICHASlbel ----------------- llnsPllel "InMtforktube 1 'O"III,IO'k lube 2 Sc .. lches/S."'dsIOamage .... Replace riDliBIID ___ _ 00 nOI """mpll0 1t,"igM." II b.", in"., lo.k IlIbe., 11111 mllvdlln, •• O"I'y ••••• n Ihllube 21nspeCI 'G'ommel Sc •• tehes/Ollm"g,,"" eplace • JOInt Id"ve ~h"nl ·Cllpld"vechllnl 6 9 7 8

CD ® I~EF~I"'I ISPECI )Ofl ® @ Ih~rlfil 1 ENG 1'-1 ® ® ICARBI'I IOR1VI.p1 (j) @ ICHASlhl I HECI iii I ® @ ~ I~~¥~? 1 (jJ) ~ @ lEJ @ ~ ® ~ @ § @ [ml @ 1 @ @ 1 1 OJ - a m ® ® @ ~ ~~ @ , A ILLUSTRATED SYMBOLS (Refer to the illustration) Illustrated symbolsCDto@aredesignedasthumb tabs to indicate the chapter's number and content. CD General informati6n ® Specifications ® Periodic inspection and adjustment @Engine ® Carburetion ® Drive train (j) Chassis @ Electrical ® Troubleshooting Illustrated symbols @ to @ are used to identify the specifications appearing in the text. @ Filling fluid (jJ) Lubricant @ Special tool @Tightening ® Wear limit, clearance @ Engine speed @n,V,A Illustrated symbols @ to @ in the exploded diagram indicate grade of lubricant and location of lubrication point. @ Apply engine oil @ Apply gear oil @ Apply molybdenum disulfide 011 ® Apply wheel bearing grease ® Apply lightweight lithium-soap base grease @ Apply molybdenum disulfide grease @ Apply locking agent (LOCrITE~)

INDEX GENERAL INFORMATION SPECIFICATIONS PERIODIC INSPECTION AND ADJUSTMENT ENGINE OVERHAUL CARBURETION DRIVE TRAIN CHASSIS ELECTRICAL TROUBLESHOOTING 0'1 GEN INFO SPEC R INSP ADJ ... ENG • CHAS ELEC ? • to--- TRBL SHTG

CONTENTS CHAPTER 1. GENERAL INFORMATION MACHINE IDENTIFICATION ..................................................................................... 1-1 VEHICLE IDENTIFICATION NUMBER (FOR USA, CDN AND AUS) ................. 1-1 FRAME SERIAL NUMBER (EXCEPT FOR USA, CDN AND AUS) ..................... 1-1 ENGINE SERIAL NUMBER ................................................................................. 1-1 IMPORTANT INFORMATION ................................................................................... 1-2 PREPARATION FOR REMOVAL AND DISASSEMBLY ...................................... 1-2 ALL REPLACEMENT PARTS ............................................................................... 1-2 GASKETS, OIL SEALS, AND O-RINGS .............................................................. 1-2 LOCK WASHERS/PLATES AND COTTER PINS ................................................. 1-2 BEARINGS AND OIL SEALS ............................................................................... 1-3 CIRCLIPS ............................................................................................................... 1-3 SPECIAL TOOLS ........................................................................................................ 1-3 FOR TUNE-UP ..................................................................................................... 1-3 FOR ENGINE SERVICE ........................................................................................ 1-4 FOR MIDDLE GEAR SERVICE ............................................................................. 1-7 FOR FINAL GEAR SERVICE ................................................................................ 1-8 FOR ELECTRICAL COMPONENTS ..................................................................... 1-9 CHAPTER 2. SPECIFICATIONS GENERAL SPECIFICATIONS .................................................................................... 2-1 MAINTENANCE SPECIFICATIONS .......................................................................... 2-4 ENGINE ................................................................................................................ 2-4 CHASSIS ............................................................................................................ 2-12 ELECTRICAL ...................................................................................................... 2-15 GENERAL TORQUE SPECIFICATIONS .................................................................. 2-17 DEFINITION OF UNITS ............................................................................................ 2-17 LUBRICATION POINTS AND LUBRICANT TYPE .................................................. 2-18 ENGINE .............................................................................................................. 2-18 CHASSIS ............................................................................................................ 2-19 LUBRICATION DIAGRAMS ..................................................................................... 2-20 CABLE ROUTING .................................................................................................... 2-22

CHAPTER 3. PERIODIC INSPECTION AND ADJUSTMENT INTRODUCTION ........................................................................................................ 3-1 PERIODIC MAINTENANCE/LUBRICATION ............................................................. 3-1 FENDERS AND FUEL TANK ..................................................................................... 3-2 FRONT FENDER .................................................................................................. 3-2 REAR FENDER ..................................................................................................... 3-3 FUEL TANK .......................................................................................................... 3-6 ENGINE ...................................................................................................................... 3-8 VALVE CLEARANCE ADJUSTMENT ................................................................. 3-8 TIMING CHAIN TENSIONER ADJUSTMENT .................................................. 3-11 IDLE SPEED ADJUSTMENT ............................................................................. 3-11 THROTTLE CABLE FREE PLAY ADJUSTMENT .............................................. 3-12 SPEED LIMITER ADJUSTMENT ....................................................................... 3-13 SPARK PLUG INSPECTION .............................................................................. 3-14 IGNITION TIMING CHECK ................................................................................ 3-15 COMPRESSION PRESSURE MEASUREMENT ............................................... 3-16 ENGINE OIL LEVEL INSPECTION .................................................................... 3-18 ENGINE OIL REPLACEMENT ............................................................................ 3-19 CLUTCH ADJUSTMENT ................................................................................... 3-21 AIR FILTER CLEANING ..................................................................................... 3-22 CHASSIS .................................................................................................................. 3-23 FRONT AND REAR BRAKE LINING INSPECTION ........................................... 3-23 FRONT BRAKE ADJUSTMENT ........................................................................ 3-24 REAR BRAKE LEVER AND PEDAL ADJUSTMENT ......................................... 3-25 DRIVE SELECT LEVER POSITION ADJUSTMENT .......................................... 3-27 FINAL DRIVE GEAR OIL LEVEL INSPECTION ................................................. 3-27 FINAL DRIVE GEAR OIL REPLACEMENT ........................................................ 3-28 DRIVE SHAFT DUST BOOT INSPECTION ....................................................... 3-29 STEERING SYSTEM INSPECTION ................................................................... 3-29 TOE-IN ADJUSTMENT ..................................................................................... 3-30 FRONT AND REAR SHOCK ABSORBERS INSPECTION ................................ 3-32 TIRE INSPECTION ............................................................................................. 3-33 WHEEL INSPECTION ........................................................................................ 3-35 ELECTRICAL ............................................................................................................ 3-35 BATTERY INSPECTION ..................................................................................... 3-35 FUSE INSPECTION ........................................................................................... 3-38 HEADLIGHT BEAM ADJUSTMENT ................................................................. 3-39 HEADLIGHT BULB REPLACEMENT ................................................................. 3-40 .1(0. t----- GEN INFO SPEC fi t----- INSP ADJ ~- t---- ..... ; ENG J-----' CARB -ra- t----- DRIV CHAS ELEC ? 1---- ..... TRBL SHTG

CHAPTER 4. ENGINE OVERHAUL ENGINE REMOVAL ................................................................................................... 4-1 PREPARATION FOR REMOVAL ......................................................................... 4-1 FRONT FENDER AND REAR FENDER ................................................................ 4-1 ENGINE OIL ......................................................................................................... 4-2 EXHAUST PIPE AND MUFFLER ......................................................................... 4-2 CARBURETOR ..................................................................................................... 4-2 STARTER MOTOR ............................................................................................... 4-3 REAR BRAKE CABLES AND FOOTREST ........................................................... 4-3 WIRINGS AND HOSES ....................................................................................... 4-3 REAR WHEEL DRIVE ASSEMBLY AND SWINGARM ....................................... 4-4 ENGINE REMOVAL ............................................................................................. 4-4 ENGINE DISASSEMBLY ........................................................................................... 4-5 CYLINDER HEAD ASSEMBLY, CYLINDER AND PISTON ................................. 4-5 STARTER PULLEY (EXCEPT FOR USA) AND CDI MAGNETO ......................... 4-8 MIDDLE DRIVEN PINION GEAR ....................................................................... 4-10 PRIMARY AND SECONDARY CLUTCHES ....................................................... 4-11 OIL PUMP AND SHIFTER .................................................................................. 4-13 BALANCER DRIVEN GEAR ............................................................................... 4-15 CRANKCASE (LEFT) .......................................................................................... 4-15 BALANCER SHAFT, TRANSMISSION AND CRANKSHAFT ........................... 4-16 CYLINDER HEAD ............................................................................................... 4-17 VALVE ................................................................................................................ 4-18 RECOIL STARTER (EXCEPT FOR USA) ........................................................... 4-19 INSPECTION AND REPAIR ..................................................................................... 4-20 CYLINDER HEAD ............................................................................................... 4-20 INTAKE AND EXHAUST VALVE ....................................................................... 4-20 VALVE GUIDE .................................................................................................... 4-21 VALVE SEAT ...................................................................................................... 4-22 VALVE SPRING .................................................................................................. 4-25 VALVE INSTALLATION ..................................................................................... 4-26 CAM SHAFT ....................................................................................................... 4-27 ROCKER ARM AND ROCKER ARM SHAFT ..................................................... 4-28 TIMING CHAIN .................................................................................................. 4-30 CAM SPROCKET AND CAM DRIVE SPROCKET ............................................. 4-31 TIMING CHAIN GUIDE ...................................................................................... 4-31 TIMING CHAIN TENSIONER ............................................................................ 4-31 TAPPET COVER AND CAM SPROCKET COVER ............................................. 4-32 CYLINDER AND PiSTON ................................................................................... 4-32 PISTON RING AND PISTON PIN ...................................................................... 4-33 CRAN K SHAFT .................................................................................................. 4-36 BALANCER DRIVE GEAR AND DRIVEN GEARS ............................................. 4-37 PRIMARY GEARS AND STARTER .................................................................... 4-37 PRIMARY CLUTCH ............................................................................................ 4-38 SECONDARY CLUTCH ...................................................................................... 4-38

1992-2000 Yamaha Timberwolf (YFB250) ATV OEM Service & Repair Manual

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