Stihl MS 660 Chainsaw Full Rebuild Tutorial!

Introduction

This tutorial provides a comprehensive step-by-step guide to rebuilding a Stihl MS660 chainsaw. Whether you are a novice or an experienced mechanic, following these instructions will help you understand the process of disassembly, inspection, and reassembly, ensuring your chainsaw runs smoothly and efficiently.

Chapter 1: Chainsaw Disassembly

To begin the rebuild, you need to disassemble the chainsaw properly.

1. Remove the Handle from the Crankcase

   • Extract the plastic keepers.
   • Use a Torx screwdriver to remove the screws.
   • Carefully remove the AV rubbers to prevent damage. Use pliers or screwdrivers as needed.

2. Extract the Crankcase

   • Unscrew the six bolts holding the two halves together.
   • Remove the two alignment pins.

Chapter 2: How to Split Chainsaw Cases

There are two methods to split the cases:

1. Using a Case Splitter Tool

   • Place the tool around the counterweights.
   • Screw it into the crankshaft to push the cases apart safely.

2. Using a Brass Hammer

   • Gently tap around the seams to split the cases.

Important Note

Inspect the bearings during this process to identify any damage.

Chapter 3: Crankshaft Inspection

After separating the cases, inspect the crankshaft and connecting rod.

1. Visual Inspection

   • Check for cracks, damage, or deformation on the bearings and cage.

2. Play Test

   • Pull the connecting rod up and down to ensure no movement occurs. Test in four positions.

3. Heat Color Assessment

   • If the crankshaft is discolored, verify the condition of the bearings to rule out overheating.

Chapter 4: How to Remove Main Bearings

To remove the bearings, follow these steps:

1. Heat the Bearing Pocket

   • Apply heat to the bearing pocket.

2. Tap Bearing Out

   • Place wood under the cases and gently tap the bearing through.

3. Clean the Pockets

   • Use Scotch-Brite to clean both bearing pockets before installing new bearings.

Chapter 5: How to Install Crankshaft Bearings

You have two effective methods for installing bearings:

1. Nut and Bolt Method

   • Lubricate the bearing and pocket.
   • Use a bolt, washers, and spaces to pull the bearing through.
   • Ensure the bearing is seated straight and smooth during installation.

2. Hot-Cold Method

   • Freeze the bearing and heat the case to about 185°C.
   • Use a brass hammer to tap the bearing into place gently.

Chapter 6: How to Install a Crankshaft

Installing the crankshaft correctly is crucial for optimal performance.

1. Apply Oil

   • Apply a small amount of two-stroke oil to the crankshaft and bearing inner race.

2. Use a Crankshaft Puller

   • Align the crankshaft with the bearing and pull it in gently using the puller.

3. Check for Preload

   • After installation, ensure the crankshaft spins freely without binding or preload.

Chapter 7: Removing Bearing Preload

If you notice binding, follow these steps to remove preload:

1. Gently Tap the Crankshaft

   • Tap each side of the crankshaft lightly to align the bearings.

2. Check Movement

   • Ensure the crankshaft rotates smoothly with minimal resistance.

Chapter 8: Installing Oil Seals

Carefully install the oil seals to avoid future leaks. Refer to a dedicated video for specific tips on this process.

Conclusion

Rebuilding a Stihl MS660 chainsaw requires careful disassembly, inspection, and reassembly. By following these detailed steps, you can ensure your chainsaw is restored to optimal working condition. The next steps involve working on the top end of the engine and preparing the saw for cutting wood. Enjoy your rebuilding journey!