It could be you need a suspension wire,they are very fine temprature compensated,some sort of steel,metal.I am just a novice and have just repaired a wind up 400 day ball clock.They have a suspension spring,it was a KERN. But I know KUNDO,also use same sort of wire.,and other ball clocks.But you must have the correct thickness for the clock.You can find out by noting any numbers or initials on the back plate,and the height of the back plate. Most suppliers of this wire will ask you for this info,and supply you with correct thickness. Its not very expensive to buy,about three pound,fifty,for three lengths..You can get it on e-bay,or internet.Hoping this helps.
Mr.James Devlin.
March 2008