I think I found the problem, if I set keys on the whole arm first, and then key the elbow it seems to have done the job.. I think I was overriding keys, or not setting the right keys on the right joints.. like moving an elbow only later would also affect the keys before it.. if you know what I mean!

Although I am very interested in like you say constrain the hand to the bike.. I was already wondering how an model could for example hold another model.. I am going to PM you with the file/project (I am about to put it on dropbox) and I highly appreciate your help!