Hi Rob,
Lost motion on the kickstart is quite common and I don’t think its related to the spring (sorry Stuart). There is a a peg which pushes on the plate that holds the starter pawl out of engagement. As the starter rotates the peg releases the plate and a spring pushes the pawl forward. It may be possible to adjust the position of the peg on its splines to get it to release the plate and thus engage the k/s a bit sooner. However, I have never seen any instructions on how to ‘time’ the k/s in any of the manuals.
Sadly the only way to resolve it is to remove the outer cover (leaving the k/s in position) to examine the parts. My explanation is rubbish but its all pretty obvious when you can look at it.
Be aware there was an earlier type of mechanism used on 4 speed engines mainly. Does the same job but in a slightly different way and is completely interchangeable but only in toto.
Regards
Peter