What model of 56 is it?
There should be a set of numbers on the silver plate.
There is a few different 56 with different drive system.
Also what do you mean by not driving right? No drive, slow, notchy?
Adjustment is usually in the middle of the cable with an inline adjuster.
Spring should be on the handle or at the gearbox on the end of the cable.
When adjusting, the spring should stretch about 13mm when lever applied or you can damage the transmission assy if you do more.
Possible slow speed is worn belts or variable speed pulley siezed but this depends on what model.
What colour is the deck as they changed the pros from green to grey?
Deck is green on this one. Excellent I will check all these things when I'm next there. Cuts lovely but just frustrating and hard work to keep pushing!