Here's a good one for you. Just in the process of stripping and rebuilding the above, engine is on the bench so decided to check valve clearances. Set the'T' mark up, but camshaft mark was out of alignment. Stuck a shaft down the plug hole to feel for TDC and found it with all valves closed on compression stroke, cam mark lined up, but 'T' mark now 90° out. So if everything at the top end is good, it must me a problem with the rotor alighnment. Noticed that the side case had been removed before as traces of silicone sealant, took case off and tried lining everything up again with no joy. Borrowed a puller and took the rotor of and sure enough the woodruff key had sheared and the rotor had turned on the shaft. Result.

Yes a result & well spotted. It's actually not too uncommon either. I've seen it on various engines over the years. Thanks for posting!

On further analysis I reckon someone has had the rotor off and put it back on with an air impact gun to cause the damage.

Hillhopper wrote: ↑Tue Mar 11, 2025 6:59 pm On further analysis I reckon someone has had the rotor off and put it back on with an air impact gun to cause the damage.

In most cases the woodruff key is not designed to take rotational load but is there to ensure that positional accuracy is maintained during assembly. It is vitally important that the taper is locked by being a perfect fit and having the correct tightening torque which must not slacken in use. If there is any damage to the taper mating surfaces it should be polished out and the surfaces lapped with grinding paste if necessary.

Roadster, a man after my own heart! Were you/are you too a tech or engineer?

Data wrote: ↑Thu Mar 13, 2025 5:57 pm Roadster, a man after my own heart! Were you/are you too a tech or engineer?

I was at least for the first half of my working life before drifting into engineering computing until I retired.

roadster wrote: ↑Fri Mar 14, 2025 9:58 am

Data wrote: ↑Thu Mar 13, 2025 5:57 pm Roadster, a man after my own heart! Were you/are you too a tech or engineer?

I was at least for the first half of my working life before drifting into engineering computing until I retired.

Thought so!