Description

Yanmar YB121U, YB151U, YB121U-2, YB151U-2 1990 Parts Catalog

If you’ve ever ordered a part for a Yanmar crawler backhoe and ended up with a box full of wrong metal, you already know why this catalog exists. I’ve been turning wrenches for 28 years, and the number one cost killer on these machines is ordering from generic aftermarket lists. This is the OEM Yanmar YB121U, YB151U, YB121U-2, YB151U-2 1990 Parts Catalog – 178 pages of factory-issued part numbers, exploded diagrams, and specs that match the machines as they left the plant. No reprints, no copy-paste jobs.

Paint Codes and Model Codes for These Yanmar Backhoes

Paint color changed in January 1989. This catalog documents both old and new formulations – old YANMAR New Light Yellow (10YR6.5/8) and new Saffron Yellow (1.0Y7.5/11). If you’re restoring a machine or ordering spray cans, the correct Munsell number is here. The paint code section lists two generations of colors. For machines built before January 1989, use YANMAR New Light Yellow (10YR6.5/8) with paint code 933110-91602 for 16-liter cans and 981101-06041 for spray. After that, the factory switched to Saffron Yellow (1.0Y7.5/11) codes 933110-91603 and 977620-30381. The catalog also includes Cream White and Dark Olive II / Charcoal Gray for undercarriage parts. Order the wrong shade and your machine looks like a patchwork job. Model codes like 172138 A (YB121U Canopy) and 172137 B (YB151U Cabin) tell you exactly which machine variant you have. Get those wrong and you’ll order the wrong decal or seat.

Does This Parts Catalog Cover the 3TNA72L-UBVM Engine?

Yes. The mounted engine is model 3TNA72L-UBVM, a vertical 3-cylinder water-cooled diesel. All engine parts are listed up in this catalog. Note that engine numbers fall into three ranges: 00501~ for early YB121U/YB151U, 10501~ for 1986 minor change, and 20501~ for YB121U-2/YB151U-2. If you order a piston ring set for the wrong range, it won’t fit. Period.

That’s the difference between a job done right and a tow truck.

3 Reasons to Use OEM Yanmar Documentation Instead of Generic Lists

One: part number accuracy across engine number ranges. Reason two: paint code changes – the catalog shows old vs new Munsell numbers. Reason three: model code differences – canopy vs cabin, option packages. Without these, you might order a canopy windshield for a cab model. Generic aftermarket catalogs often combine variants or miss supersessions. This OEM catalog has three editions – the 3rd edition from December 1990 (pub. no. 000Y00K2103) discards the old ones. You get the latest parts information.

Safety is another reason to stick with OEM data. A wrong hydraulic seal can blow out under pressure, causing injury or fire. The factory catalog gives you the exact part and the correct orientation for installation. Generic lists might cross-reference a seal that’s close but not rated for the Yanmar system pressure. Close doesn’t count in this trade.

Understand the Engine Number Range Before Ordering Parts

Engine number location is stamped into the machine. The table in the preface is critical. It shows that YB121U and YB151U (without dash-two) share engine numbers up to 00501 and then 10501 with minor change. The dash-two models start at 20501. That means some parts are interchangeable, some are not. You need the engine number to decide. Find the serial number stamped into the machine frame near the engine. Cross-reference it with the table. If your machine has engine number 10500, it’s not covered – the catalog starts at 00501 and 10501. This level of detail prevents ordering parts that physically fit but are rated for different power output. The Automotive Industry Overview might teach you about vehicle classifications, but it won’t tell you which Yanmar fuel filter fits your machine.

Dimensions and Specifications: What the Catalog Lists

Page 3 of the original catalog gives transport length (3440 mm for canopy models), transport width (960–1020 mm), transport height, bucket capacity (0.06 m³), digging depths, travel speed 2.0 km/hr, gradability 30 degrees, ground pressure. You need these numbers to order the right track tensioner and shoes. Wrong ground pressure rating can cause premature track wear. The catalog also lists model-specific data for YB121U-2P, YB121U-2C, YB151U-2P, YB151U-2C. You need that detail to get the right track shoe width.

For related Yanmar parts catalogs, check the Ammann Yanmar B12 B17 Parts Catalog and the Yanmar YB271, B27 1994 Parts Catalog – OEM Factory Specs. Also the Yanmar YB301 YB351 1991 Parts Catalog – 248 Pages OEM covers larger models. Reading the Automotive Industry Overview won’t get you the part number you need – only the factory catalog will.

FAQ

What models does this parts catalog cover?

YB121U, YB151U, YB121U-2, YB151U-2 crawler backhoes with engine numbers starting 00501, 10501, or 20501.

Does the catalog include wiring diagrams or service instructions?

This is a parts catalog only – it lists every component with OEM part numbers and exploded views. It does not contain torque specs, repair procedures, or wiring diagrams. For those, you need the corresponding service manual. But for ordering the correct hydraulic hose, final drive seal, bucket tooth, or even the decal for the control panel, this is the only source you should trust. Aftermarket lists often omit supersessions or change-over points that this catalog documents across its 178 pages. For example, the engine number range split means the same pump might have a different part number after serial 10501. Without this catalog, you’re gambling with your money and your time.

How do I find the part number for the main hydraulic pump?

Locate the machine model and engine number range in the preface. Then turn to the chassis section. The catalog groups parts by functional assembly – hydraulic system, engine, undercarriage. Use the index or exploded diagrams. If you still can’t find it, check the model code (e.g., 172138 A) to ensure you have the correct variant.

Is this the same as a service manual?

No. It’s a parts catalog, not a service manual.

If you’re working on a Yanmar YB121U or YB151U series, this catalog saves you from ordering the wrong part and eating the cost. Get the exact OEM data – Access the Factory Manual.