Honda CB125 & CB160 1972 Workshop Manual – Factory Specs

Description

If you are working on a 1972 Honda CB125 or CB160 and you are relying on a Clymer or a random PDF from a forum, you are asking for trouble. I have seen more than one engine ruined because some kid used a torque wrench setting from a third-party book. This is the real thing: the Honda CB125, CB160 1972 Workshop Manual published by Honda Motor Co., Ltd. in 1972. 139 pages of factory engineering, not a reprint, not a scan of a scan. Every specification in this book came from the same engineers who designed the bike. That is the only source you should trust when you are inside the engine or the frame.

The manual is split into six sections, but the two big ones are Section III (Engine) and Section IV (Frame). If you are rebuilding the top end, you need the cylinder head and cylinder procedure starting on page 12. That section covers the head gasket surface, valve clearance, and the actual torque sequence for the cylinder head nuts. I have seen mechanics skip the sequence and warp the head. Page 12 gives you the order and the foot-pounds. Do not guess. The rest of the engine section covers the clutch, oil pump, transmission, kick starter, and the carburetor. The carburetor section is especially useful if you are trying to get a 1972 CB125 to idle after sitting for twenty years.

Engine Section: Cylinder Head and Cylinder – Page 12

This is the part most people mess up. The manual shows you exactly how to disassemble the cylinder head and cylinder, including the orientation of the cam chain, the alignment marks, and the correct torque values for the cylinder head nuts. I have used this procedure on a CB160 that had a blown head gasket. The manual tells you to replace the gasket and the O-rings, and it gives you the torque in foot-pounds. It also warns you about the dowel pins. That is the kind of detail you do not get from a Haynes manual. If you are working on a CB125 or CB160, you need this page open on your bench.

3.2 Cylinder Head and Cylinder – Factory Procedure

Page 12 is where the real work happens. The manual walks you through removing the cylinder head, then the cylinder, and then the piston. It tells you to mark the cam chain before you break it loose. It gives you the torque sequence for the cylinder head nuts in three stages. I have seen guys try to torque these in one pass and strip the threads. The manual says to torque in stages, from the center out. That is the difference between a good rebuild and a leaky mess. The same section also covers the cylinder base gasket and the piston ring gaps. If you are doing a top-end job, you cannot afford to miss this.

Does This Manual Cover the Frame?

Yes, Section IV covers the frame from handlebar to rear wheel. The front wheel procedure starts on page 73. That includes the front axle torque, the spoke adjustment, and the brake disassembly. The rear wheel is on page 77. The manual also includes the steering stem, the fuel tank, the exhaust pipe, and the rear cushion. If you are restoring a 1972 CB125 or CB160, the frame section gives you the factory specs for the swingarm pivot, the rear shock absorber settings, and the fork oil level. The fork oil capacity is in the specifications section, but the procedure is in the frame section. You need both.

Get the Right Torque Data

Torque specs are scattered throughout the manual, but the main specs are in Section II (Specifications) and in the individual procedures. The engine torque values for the cylinder head, connecting rod bolts, and flywheel nut are all in foot-pounds. The manual uses metric wrench sizes, but the torque values are in foot-pounds. I have seen people try to convert from a Haynes manual and overtorque by 20%. That is how you strip a thread. Stick with the factory numbers. The manual also includes the oil capacity, the spark plug gap, and the valve clearances. All of that is in the specifications section. If you are rebuilding a 1972 CB125, you need those numbers.

Why OEM Specs Matter

Aftermarket manuals are written by people who may have never touched a Honda engine. This manual was written by Honda engineers. The difference is in the details. The manual tells you the exact sequence for the cam chain tensioner adjustment. It gives you the clearance for the cam chain guide roller. It shows you the oil pump disassembly and the filter cleaning procedure. I have used this manual to rebuild a CB160 transmission. The gear shift section on page 44 shows you the exact alignment of the shift forks. If you try to guess that, you will end up with a transmission that jumps out of second gear. The factory manual eliminates that guesswork. You can get the same results if you follow the procedures.

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For more information on the automotive industry and the importance of OEM documentation, see Automotive Industry Overview and Automotive Industry Overview.

FAQ

Does this manual cover both the CB125 and CB160?

Yes. The manual covers both models. The specifications are listed separately for each engine displacement. The procedures are the same unless noted.

Are the torque values in foot-pounds or Newton-meters?

>Foot-pounds. The manual uses imperial units for torque. All values are from the factory.

What is the page count and format?

The manual is 139 pages, published in 1972 as a printed workshop manual. The digital version is a PDF scan of the original. It includes the full table of contents and all illustrations. The text is in English. The page count includes the preface and specifications. The engine section starts on page 8 and runs to page 50. The frame section runs from page 53 to 77. The rest of the manual includes the features, specifications, and appendix. The digital format is searchable, but the images are scanned. You can print the pages you need.

Can I use this manual to rebuild the transmission?

The transmission section is on page 41. It covers the disassembly, the gear shift mechanism, and the kick starter. The manual includes the washer thicknesses and the circlip locations. If you follow the procedure, you can rebuild the transmission without pulling the entire engine. The manual also shows you how to align the shift forks. It is the same procedure the dealership used.

If you are serious about keeping your 1972 Honda CB125 or CB160 on the road, you need the factory documentation. Don’t rely on aftermarket summaries or forum advice. Access the Factory Manual and keep it on your bench. It will save you from buying parts you don’t need and from making mistakes that cost time and money. The 139 pages of OEM procedures are the only guide you should trust.