Can the lever handle return spring be replaced?

For our lever handle set model: SK1215, BK1216, SKGLW, HK01-I, HK357DB05, and SKAJL

No, our lever handle return spring cannot be replaced by user.

The return spring is permanently assembled in the outside housing, it isn't user accessible. 

Plus, we do not stock the return spring as spare part.

If you can access to the return spring of the handle, then the handle set is not made by Ideal Security Inc.