Woodruff key

I think I might have a worn woodruff key. When the bike is idle it rattles but when I hold the clutch down it stops. Is it important that I get the woodruff key changed? Will it cause severe damage to the bike if I don't?

Is this your first KTM?  What year and model?  These bikes make a knocking sound when idling in neutral that goes away when you pull the clutch in, that's normal. 

Is this your first KTM? What year and model? These bikes make a knocking sound when idling in neutral that goes away when you pull the clutch in, that's normal.

Yeah it's my first KTM.

2005 KTM 450 exc

Find someone else with a KTM and listen to their bike idle and see if yours sounds similar. If so then you're most likely fine.

Find someone else with a KTM and listen to their bike idle and see if yours sounds similar. If so then you're most likely fine.

But if it is the woodruff key you think I will be okay?

If you think there's a bad woodruff key in there then take it apart and check it out.

The only bike that I can remember having a Woodruff Key issue was the 2003 WR450.  They did a recall and the issue was fixed for the 2004.  I never heard of any KTM's having this issue.

Early yz400's and maybe the first yz426 had a key on the crank gear also. Look at the KTM manual to make sure there is one before testing it apart.

Yes the woodruff key could be worn or the crank nut on the left side has lost its torque. My 05 450 MXC started making a louder than normal clutch noise, took the clutch apart and it looked pristine. Grabbed the crank nut, which is left hand thread and it was loose. Took the nut off and had very little play and the woodruff key was in good shape. Cleaned the threads, red lock tight and torqued to 150 nm. Let it dry overnight, reassembled and the noise is gone. I'm going to get a key and replace it next time I'm in there.

Yes the woodruff key could be worn or the crank nut on the left side has lost its torque. My 05 450 MXC started making a louder than normal clutch noise, took the clutch apart and it looked pristine. Grabbed the crank nut, which is left hand thread and it was loose. Took the nut off and had very little play and the woodruff key was in good shape. Cleaned the threads, red lock tight and torqued to 150 nm. Let it dry overnight, reassembled and the noise is gone. I'm going to get a key and replace it next time I'm in there.

Sorry I said left side, it's the right side- clutch side.

Yes the woodruff key could be worn or the crank nut on the left side has lost its torque. My 05 450 MXC started making a louder than normal clutch noise, took the clutch apart and it looked pristine. Grabbed the crank nut, which is left hand thread and it was loose. Took the nut off and had very little play and the woodruff key was in good shape. Cleaned the threads, red lock tight and torqued to 150 nm. Let it dry overnight, reassembled and the noise is gone. I'm going to get a key and replace it next time I'm in there.

What can happen if I leave it as it is? Can more complications arise?

I'm sure there are loose crank nuts running down the road right now, IMO the right side of the crank shaft holds the freewheel hub which is part of the electric start gearing. If the nut is not torqued the hub is loose and moving on the crank shaft, if left unaddressed you could damage the hub and more importantly the crank shaft.

Its an easy job if you have basic mechanical ability and tools. Just get a clutch cover gasket, clutch nut locking tab and a new woodruff key.

Let us know how it goes.

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