Pulsar C13 Timing Chain and Sprocket Qs & Workshop Manual

[Many_methods]

Hi,

I am in the process of replacing the timing chain and sprockets on my 2015 Pulsar (70k miles). 

I'm now at the point of taking the sprockets off the camshafts but not sure how I do this. Is is just the bolt in the centre of each sprocket that needs undoing? Standard thread for both?

I also now need a workshop manual to find all the torque settings as part of the rebuild. Can anyone provide a link or suggest a good manual to buy? Of course, if anyone has a list of the torque settings they could share, that would be perfect!

Finally - any ideas what may have caused the chain and sprockets to wear at this low mileage? The chain had stretched and was noisy. On removal I've noticed the tensioner was ok but the chain was clearly stretched and all sprockets are well worn - particularly on the crankshaft. I have only owned the car for the last 2 years and the car had been regularly serviced prior to that. 

Sorry for all the questions on my first post but I appreciate all responses.

Thanks