Remove and refit a flywheel (rotor) with a puller

The flywheel (also called the rotor) carries magnets and sits on a tapered end of the crankshaft. It must come off to reach the stator coils, pick-up or points under it. The taper grips hard. The correct puller threads into the flywheel and pushes on the crankshaft end. It lifts the flywheel without force on the casting.

Safety

• Do not hit the flywheel, lever it off, or use a general gear puller on its rim. Flywheels crack and the cost is high.
• The flywheel spins fast. A loose nut or a cracked rotor can fly apart. Tighten the nut to the manual's torque.
• Keep fingers clear of any pinch between the puller and the casting.

You need

• A puller made for your engine. The thread in the flywheel centre differs between models.
• A holding tool or strap to stop the flywheel turning while the nut is loosened and tightened.
• The torque value for the nut.

Steps

1. Remove the flywheel cover. Disconnect the battery if there is one.
2. Mark the position of the flywheel on the crankshaft with a paint pen if the manual says to. Keep the key.
3. Hold the flywheel with the holding tool and undo the centre nut.
4. Remove the washer. Check the nut and washer are not damaged.
5. Screw the puller into the flywheel until it is fully engaged, then tighten the centre bolt of the puller against the crankshaft.
6. Keep the puller bolt snug. If the flywheel does not release, tap the end of the puller bolt lightly with a hammer. The shock helps break the taper. Do not tap the flywheel.
7. Lift the flywheel off. Keep the woodruff key. Wipe the taper and the flywheel bore. Check them for damage.
8. Do your work on the coils or points.
9. Refit: line up the key and the slot. Slide the flywheel on without force.
10. Fit the washer and nut. Hold the flywheel with the tool and tighten to the manual's torque.
11. Check the air gap between the pick-up and the flywheel if the manual gives one.
12. Turn the engine by hand. It must turn freely with no rub.

Check your work

• No scraping noise when the engine turns.
• The nut is tight to the specified torque.
• Wiring is routed clear of the flywheel.

If it did not fix the problem

• Test the stator (generator coils).
• Test the ignition pick-up.
• Set points timing on a flywheel magneto.