Sheared woodruff key on intake cam

[safetyfish]

History: Performed a major service and dialed in the cams. Used OEM parts on everything (roller retaining screws, special roller nut eg.) and then everything went back together as per OEM torque values. Loctite etc

Engine was rotated by hand to check binding and all was OK, started the bike and sorted the idling etc with no issues whatsoever.

Took the bike for a ride when suddenly I lost power after about 5 miles and the bike died within meters of it loosing power. Pushed the bike home and found that the intake cam roller was "off" in comparison to the exhaust roller.

Disassembled the lot and found that the woodruff key was sheared in half on the intake camshaft. How on earth is this even possible? I really do not want to remove the cylinder head to confirm that the valves and the piston is OK.

Any ideas as to why or how this happened?

[DukeDesmo]

Looks like it was not torqued correctly at some point, so that all the load was on the key.

Hope the valves & piston are OK...

[safetyfish]

Originally Posted by DukeDesmo

Looks like it was not torqued correctly at some point, so that all the load was on the key.

Hope the valves & piston are OK...

From my limited knowledge my first guess was also incorrect torque or....
the intake valves on the way down met the piston on the way up and inertia did its best resulting in what I have now.

[moperfserv]

The key only holds the parts in alignment while the fastener is being torqued. From that point the tension/friction handles the load.
The sheared key indicates that the fastener didn't have sufficient torque to hold the parts.
In other words, I agree with the previous two posters.

Do you have all of the 'factory' tools for that operation?

Doug

[safetyfish]

Originally Posted by moperfserv

Do you have all of the 'factory' tools for that operation?

Doug

I used a roller holding tool and the special 4 pronged socket to torque up the new castellated nut. Seems that somehow I did manage to f*ck it up somehow....

SF

[lameshaft]

How come the pulleys had to come off of the cams in the first place?
Bad oil seal?

Sorry, but your head will def have to come off.
Piston may be ok, but surely you bent valves.

[efiniGTX]

I have only seen that happen in small snow blower and salt spreader engines. The flywheel is keyed and when there is enough resistance to the direction of rotation the key shears (eg: pushing heavy wet snow through the machine or a rock jams the auger). If you say that you rotated the engine by hand then a restrictive force is unlikely. If the part was not torqued enough the gear basically slams into the key in the small amount of space available.

[fastcan]

I sheared one on an exhaust cam back in the fall.
I was equally surprised when you consider how easy the cams are to turn on a duc.
Mine was one of the offset keys, and I assumed it was defective.
I don't necessarily buy that the woodruff key is only for lining things up.
Anyway, I had a crank shop build up and machine the cam, new keys and found a set of adjustable pulleys instead of the offset keys.(how many miles have been logged with the offset keys I couldnt guess)
Bent valve problem as well.

[pgeller]

Bummer about that! Don't blame yourself, you're not alone. My '08 Multi 1100s ate a cam key at 48 miles on the odo, so even the factory gets it wrong. That one ended badly, with the remainder of the horizontal rod poking intothe transmission. Crunch.

Pg
DD

[Dmitry]

I sheared plenty of keys on my vintage scooters (flywheel) usually insufficient torque, however in your case it could be a sign of bearing failure.