the lock screw is to hold it in while you assemble the thing. after thats its not used.
ChrisU, I didn't want to shout straight away, but I was pretty sure that this statement was 100% wrong but I wanted to check in my Genuine workshop manual before opening my big gob.
The cam chain is tensioned when one of the pistons is at TDC, doesn't matter which. The lock nut is released and the bolt slackened off. This allows the spring to put the correct tension on the cam chain. The bolt is then tightened up to the correct torque setting and then the lock nut is also tightened to stop it from moving. Basically the spring is for pre-tension and I would imagine were it to be allowed to do it's own thing then there is a danger of something going catastrophically Pete Tong!
