Tighten your flywheel properly!

Our spare bike was bought as a non-runner. The owner said the engine made bad noises when it broke down….several years ago.

When we took off the left crankcase cover, the flywheel was loose, no puller needed! The stator was toast, but to our surprise, the starter clutch was in good condition.

Part of Fig. 2.20 Haynes Workshop Manual

What happened to the crankshaft in the above photos? The flywheel came loose because the end bolt loosened, it probably was not tight enough. What did not break is the small woodruff key (red arrow) that fixes the location flywheel – crankshaft. The heavy flywheel began to rock the small woodruff key in its cradle. I would expect the woodruff key would break in two parts. It did not break. It broke parts left and right from the crankshaft, making this otherwise impeccable part useless, except as a convincing argument to tighten your flywheel real hard, that means to 80 Nm (for our Anglo-Saxon friends: 58 Ft-lb).

Detail of the broken crankshaft. The red arrow indicates the nut for which the 46 mm

spanner is so useful. See below.