Part of the Yanmar Parts Manuals.
Need the factory part numbers for your Yanmar 4TN78TL or 4TNA78TL-DBWVM engine? This 46-page parts catalog (OEM #Y00B3322) covers the full engine family, including the 4TNA78TL-RBW and YB401W variants. Inside, you get exploded-view diagrams for every major assembly: governor rack and pinion, control lever bracket, starting motor, generator, magnetic relay, and the complete gasket and tool set. Each diagram pairs component illustrations with OEM part numbers and cross-references so you can identify exactly what to order before you pick up the phone. The main bearing undersize for 4TNA78TL-DBW and RBW variants is listed at 0.25 U.S.; V-belt type is A-38. Wrong part, wasted trip. Bookmarked by system, this PDF opens on any device; pull it up at the parts desk and have the right number ready before you say a word.
What's Inside This Yanmar 4TN78TL / 4TNA78TL Series Parts Manual
| System | Pages | Key Topics |
|---|---|---|
| Governor | 33-34 | Lever Bracket, Joint Retainer, Circlip, Pin |
| Control Lever Bracket | 35-36 | Starter, Pinion Stopper Set, Pinion Stopper Clip, Field Coil Assy, Pore Core Screw Set, Brush, Rear Cover Assy, Rear Cover Metal |
| Starting Motor | 37-38 | Generator, Rotor Assy, Spacer, Stator Assy, Rear Cover Assy, Regulator Brush Assy, Brush Assy, Regulator Assy |
| Generator | 39-40 | Earth Cord, Cord, Magnetic Relay, Bolt |
| Magnetic Relay | 41-42 | Dust Filter, Air Cleaner Assy, Outer Element, Cleaner Body, Air Cleaner Cup, Baffle, Inner Element, Unloader Valve |
| Tropics & Desert Type | 43-44 | Gasket Set, Cylinder Head Gasket, Hydraulic Oil Pump Gasket, Oil Seal Case Gasket, Bonnet Gasket, Suction Manifold Gasket, Exhaust Manifold Gasket, RHB31 Turbo Gasket |
| Gasket Set & Tool | 45-46 | Gasket Set, Gasket, Cyl. Head, O-Ring, HYD.OIL Pump, SUC.MANIFOLD |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Main Bearing Undersize | 0.25 U.S. | p. 2 |
| Bearing Pin Undersize | 0.25 U.S. | p. 16 |
| Piston Ring Set Oversize | 0.25 | p. 16 |
| V-Belt Type | A-38 | p. 22 |
| Ball Bearing Size | 13/32 | p. 18 |
| Wire Diameter | 0.6 | p. 32 |
| Governor Link Length (Mark 05) | 30.5 | p. 31 |
Yanmar 4TN78TL / 4TNA78TL Series Common Problems This Manual Covers
Need the correct governor link part number for a Yanmar 4TNA78TL-DBW engine surging at idle p. 33
Check the parts breakdown on page 33 for the control bush and rack pinion components. Verify the Mark 05 governor link length is 30.5 on page 31 before ordering your replacement linkage to ensure correct fitment and resolve the surging issue.
Manual Section: GovernorCannot locate the correct undersize bearing pin part numbers after finding low oil pressure and knocking p. 45
Inspect the engine parts diagram on page 16 to find the 0.25 U.S. undersize bearing pin part numbers. Review the complete gasket set and tool list on page 45 to ensure you order all necessary cylinder head and suction manifold O-rings for reassembly.
Manual Section: Gasket Set & ToolNeed the severe duty air cleaner assembly exploded view because the engine is ingesting heavy dust p. 43
Review the Tropics & Desert Type breakdown on page 43. Locate the correct part numbers for the outer element and dust filter body. Check the V-belt type A-38 listed on page 22 and add a fresh belt to your maintenance order while replacing the filtration components.
Manual Section: Tropics & Desert TypeNeed to order replacement internal bearings and field coils for a starter grinding during engagement p. 37
Examine the starting motor exploded view on page 37. Identify the correct part numbers for the center bearing assembly, field coil, and starter stopper set. Verify your ball bearing size is 13/32 on page 18 to ensure you order the exact match for your specific starter variant.
Manual Section: Starting MotorFrequently Asked Questions
What are the replacement specifications for fuel filter?
The manual identifies the fuel filter element as "ELEMENT, FUEL" with part number 129100-55650, as shown in Fig. 14 on page 30. It also lists a "STRAINER ASSY, FUEL" with part number 129100-55621. However, the manual does not provide specific replacement specifications such as micron rating, flow rate, or recommended replacement intervals.
What are the replacement specifications for oil filter?
The manual identifies the oil filter as "FILTER 90X80L" with part number 129150-35150, as depicted in Fig. 9 on page 19. The manual provides the part number for replacement but does not include specific replacement specifications such as micron rating, flow rate, or recommended replacement intervals.
What governor and rack pinion parts are listed in the catalog?
Check the parts breakdown on page 33 for the control bush and rack pinion components.
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