Table of Contents
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GEN
INFO
IDENTIFICATION ............................................................................................ 1-1
SERIAL NUMBER .................................................................................... 1-1
STARTING SERIAL NUMBERS ............................................................... 1-1
SAFETY WHILE WORKING ........................................................................... 1-2
FIRE PREVENTION .................................................................................. 1-2
VENTILATION .......................................................................................... 1-2
SELF-PROTECTION ................................................................................. 1-2
OILS, GREASES AND SEALING FLUIDS ............................................... 1-2
GOOD WORKING PRACTICES ............................................................... 1-3
DISASSEMBLY AND ASSEMBLY ........................................................... 1-4
SPECIAL TOOLS ............................................................................................ 1-5
MEASURING ........................................................................................... 1-5
REMOVING AND INSTALLING ............................................................... 1-7
FEATURES AND BENEFITS ........................................................................... 1-8
POWER UNIT ........................................................................................... 1-8
IGNITION SYSTEM ................................................................................. 1-9
IGNITION TIMING IN NEUTRAL .......................................................... 1-10
COOLING SYSTEM ................................................................................1-11
TILLER HANDLE .................................................................................... 1-13
BRACKET AND BOTTOM COWLING ................................................... 1-14
TECHNICAL TIPS ......................................................................................... 1-15
CARBURETOR ....................................................................................... 1-15
IGNITION SYSTEM ............................................................................... 1-18
CHAPTER 1
GENERAL INFORMATION
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Table of Contents
Related Manuals for Yamaha 25BMH
Summary of Contents for Yamaha 25BMH
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Page 1: Table Of Contents
INFO CHAPTER 1 GENERAL INFORMATION IDENTIFICATION .................... 1-1 SERIAL NUMBER ..................1-1 STARTING SERIAL NUMBERS ............... 1-1 SAFETY WHILE WORKING ................1-2 FIRE PREVENTION .................. 1-2 VENTILATION ..................1-2 SELF-PROTECTION ................. 1-2 OILS, GREASES AND SEALING FLUIDS ..........1-2 GOOD WORKING PRACTICES ............... 1-3 DISASSEMBLY AND ASSEMBLY ............ -
Page 2: Identification
Model name Approval model code Transom height Serial number STARTING SERIAL NUMBERS The starting serial number blocks are as fol- lows: Model name Approval Starting serial model code number Worldwide S:020101 25BMH L:350101 30HMH S:050101... -
Page 3: Safety While Working
The procedures given in this manual are those recommended by Yamaha to be fol- l o w e d b y Ya m a h a d e a l e r s a n d t h e i r mechanics. -
Page 4: Good Working Practices
SAFETY WHILE WORKING INFO Under normal conditions or use, there should be no hazards from the use of the lubricants mentioned in this manual, but safety is all-important, and by adopting good safety practices, any risk is minimized. A summary of the most important precau- tions is as follows: 1. -
Page 5: Disassembly And Assembly
SAFETY WHILE WORKING INFO 3. Non-reusable items Always use new gaskets, packings, O- rings, split-pins, circlips, etc., on reas- sembly. DISASSEMBLY AND ASSEMBLY 1. Clean parts with compressed air when disassembling. 2. Oil the contact surfaces of moving parts before assembly. 3. -
Page 6: Special Tools
SPECIAL TOOLS INFO SPECIAL TOOLS Using the correct special tools recom- mended by Yamaha, will aid the work and enable accurate assembly and tune-up. Improvising and using improper tools can damage the equipment. MEASURING Dial gauge set P/N. 90890-01252 Crank stand alignment P/N. - Page 7 SPECIAL TOOLS INFO Cylinder gauge P/N. 90890-06759 Outside micrometer P/N. 90890-03006 P/N. 90890-03008 Inside micrometer P/N. 90890-03010 Thickness gauge P/N. 90890-03079 Shimming plate P/N. 90890-06701 Pinion height gauge P/N. 90890-06702 Magnet base P/N. 90890-06705 Backlash indicator P/N. 90890-06706 Magnet base plate P/N.
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Page 8: Removing And Installing
SPECIAL TOOLS INFO REMOVING AND INSTALLING Flywheel puller P/N. 90890-06521 Flywheel holder P/N. 90890-06522 Small end bearing installer P/N. 90890-06527 Bearing separator P/N. 90890-06534 Stopper guide plate P/N. 90890-06501 Bearing housing puller claw P/N. 90890-06564 Center bolt P/N. 90890-06504 Drive shaft holder 3 P/N. -
Page 9: Features And Benefits
FEATURES AND BENEFITS INFO FEATURES AND BENEFITS POWER UNIT The 25B and 30H engines are designed to provide superior fuel economy, serviceability, and durability. They are based on the previous 25V and 30G with newly designed linkage that controls both throttle opening and ignition timing mechanically and simultaneously. -
Page 10: Ignition System
FEATURES AND BENEFITS INFO IGNITION SYSTEM Ignition system on the 25B and 30H consists of flywheel magnet, charge coil, pulser coil, CDI unit, and ignition coil. Similar to the previous 25V and 30G, the engine has the mechanical ignition timing advance system that works by way of the linkage. -
Page 11: Ignition Timing In Neutral
FEATURES AND BENEFITS INFO IGNITION TIMING IN NEUTRAL As the throttle is opened while the shift in neutral, the Lever moves to the right until it touches the Arm , and ignition timing advance is stopped at the point "A". The Arm moves to the right or to the left when the shift is engaged, since it is interlocked with the shift lever. -
Page 12: Cooling System
FEATURES AND BENEFITS INFO COOLING SYSTEM New structure applied to the cooling system provides additional cooling capacity in the upper casing. With additional cooling water passage (indicated by ), water walls contained in the new upper casing contribute to the reduction of outer surface temperature. Fig. - Page 13 FEATURES AND BENEFITS INFO COOLING SYSTEM Fig. 7 1-12...
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Page 14: Tiller Handle
FEATURES AND BENEFITS INFO TILLER HANDLE For the throttle grip on the steering handle of the 25B and 30H, 100 degrees of opening angle covers all ranges from full-close to wide-open positions. Also, new steering handle parts were developed to assume the long use. Inner diameter of the steering handle engagement area, and both inner and outer diameters of steering bracket are increased. -
Page 15: Bracket And Bottom Cowling
FEATURES AND BENEFITS INFO BRACKET AND BOTTOM COWLING The Bracket 1 is modified on the 25B and 30H, and newly designed rubber seal is added to provide better sealing ability for the bottom cowling. Fig. 10 1-14... -
Page 16: Technical Tips
TECHNICAL TIPS INFO TECHNICAL TIPS CARBURETOR (1) Slow air jet (idling and slow speed operation) Since the throttle valve is almost closed at low speeds, and thus the vacuum at venturi is small, air/fuel mixture is not delivered through the main nozzle. At idling, the fuel delivered from the pilot jet is mixed with the air delivered from the pilot air jet. - Page 17 TECHNICAL TIPS INFO (2) Mid range As the throttle valve opens in the mid-speed range, air/fuel mixture is fed through the bypass holes in addition to the delivery through the pilot outlet. Air/fuel mixture is also delivered through the main nozzle depending on the throttle valve opening.
- Page 18 TECHNICAL TIPS INFO (3) High engine speed In the high engine speed where the throttle valve is fully open, the fuel delivered through the main jet is mixed with the air delivered through the main air jet, which is fed into the venturi through the main nozzle.
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Page 19: Ignition System
TECHNICAL TIPS INFO IGNITION SYSTEM The 25B and 30H use the mechanical ignition timing advance system, in which the base of the charge coil and the pulser coil slides in accordance with the throttle valve opening. Mechanical ignition timing advance applied in this system makes it easier to adjust and confirm the appropriate ignition timing.