How did it get unwound.. IF the spring got unwound due to some error like leaving it out in a wind storm that broke the arm.. It is easy... But if it suddenly went SPRRROOONNNGGGGG without nothing outside the tube being broken... You gonna need a replacement.
Tools needed,, A small metal rod roughly 1/8" diamater but I can not give you the proper size without finding the proper rod.. A drill bit may work here.
And a wrench. You may also need vice grips.
I won't describe the procedure though as there is too great a chance of injury if you have to ask how to do it.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times