Mower - Autodrive poor after belt change

[Dr Murdoch]

I've just replaced the belts on my Hayter 41, and I've now got very poor drive. The roller turns but has what I can only describe as 'little toque'. I've maxed out on the adjustment of the clutch cable.

What else could be causing this, I appreciate that I may have put it back together incorrectly, if I have then I'm not certain where to start looking. Any tips greatly appreciated.