Yamaha YZF R125 engine strip

Yamaha YZF R125 engine strip , cases split , gearbox , engine repairs 

This is a post showing you a strip down of a whole bottom end if you need any advice its best to visit the dedicated posts for each section.

⚠️ SAFETY FIRST: This is an advanced repair. Ensure you have a clean workspace, the correct tools, and a factory service manual before splitting the engine cases.

Learn the process for a complete Yamaha YZF-R125 engine strip-down and bottom-end repair. This guide covers removing the clutch side cover, splitting the crankcases using the built-in tabs, and identifying critical balance shaft timing marks.

Key Technical Highlights:

• Case Splitting: Guidance on using the Yamaha-provided tabs to gently separate cases without damaging the mating surfaces.

• Timing & Alignment: Visual reference for balance shaft gear timing marks essential for reassembly.

• Critical Components: Important warning regarding the clutch actuator pin ball bearing which is easily lost during disassembly.

• Gearbox Layout: Detailed photos of the gearbox assembly to assist with correct gear and shim placement during rebuild.

Torque Specifications & Technical Data

To complete this guide, you should note these additional torque settings for the bottom end:

• Crankcase Bolts (M6): 10 Nm (1.0 m·kg, 7.2 ft·lb) — Tighten in a staged, criss-cross sequence starting from the center.

• Balance Shaft Gear Bolt: 60 Nm (6.0 m·kg, 43 ft·lb)

• Oil Pump Bolts: 7 Nm (0.7 m·kg, 5.1 ft·lb)

• Stator/Generator Cover Bolts: 10 Nm (1.0 m·kg, 7.2 ft·lb)

Pro Tip: When splitting the cases, "slow and steady" is the rule. If the cases don't separate with gentle pressure on the tabs, double-check for a missed bolt (often hidden behind the sprocket area or under oil residue). Never use a screwdriver to pry the mating surfaces, as this will cause permanent oil leaks.

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removing the clutch side cover

use a 2 pence piece here to lock gears to hold for removal of this tight bolt

remove clutch see our post here on that 

then remove all other components , best to photo them for ease of replacement or use mine .

Balance shaft gear timing marks 

Beware of this ball bearing for the clutch actuator pin 

As you see Yamaha give you little tabs to help you separate the cases it can take some time just go gentle and steady until things start to move make sure all bolts are removed though as you will always miss one .

a few gear box shots for you for rebuilding 

Need engine parts try un Ebay UK  here