Wr390 1980 Kickstart Not Returning Anymore

Hi I Just finished a Vintage enduro today on my trusty WR390 1980 and the Kickstart lever unfortunately now doesn't return to the top position anymore. It looks like the spring must be inside of the left hand cover. Is this spring failing a common problem? If so can anyone please explain what is the usual fix and what is involved to remove the left hand cover as I do not have any manuals. So far I have done a google search and have only found part 3 of a video where someone modifies the broken spring, the other 2 video parts seem to be missing on YouTube.

Here is a Service Manual to start with (Thanks to SteveJ):

https://onedrive.live.com/?authkey=!AKkEZ82cP3I-3kc&cid=2953AAE2DD855B48&id=2953AAE2DD855B48!243&parId=root&o=OneUp

-And a Parts Manual:

https://www.hva-factory.com/catalogue

Thanks for that VinsKord, I ended up just leaving the left kick lever and gear lever in place and then removed the LH case cover. The return spring is broken as you can see in this picture and I have now ordered a new one from HVA along with a new kick lever rubber