Need help with a 1992 KTM 250 MX

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I have a friend who brought me his 1992 KTM 250 MX.  Oil keeps coming out of the cap when he rides it.  I think it's a defective one way vale inthe damping rod.  Can anyone confirm this?  And, if so, is there a replacement seal or fix for this?  Also, his cap clicker doesn't click.  It looks like someone tried to force the cap back on wrong and bent the guide dogs on the cap.  Any diagrams of exactly how this comes apart or such would be appreciated.