Well you do need to take it off to fix it ...so .....
There is simple spring under the cover that bears on the underside that adds tension..
on originals it is flat spring held with 1 screw
on Uberti's it a coil spring
simply remove the one screw in the top cover and slide the cover to rear , the locator will slide out.
Cock the hammer and the cover will continue to the rear and detach ( be careful here, as the spring will try to leap out ..
you either replace the spring or try to stretch a bit for more tension, one other option would to add 1 # 8 steel shot in the hole then the spring.
On originals remove the flat spring hold down screw and replace the flat spring, Available from Winchester Bob