Front derailer wont stay on largest chain ring

[dixonia]

Hi I have just purchased a new Dawes 200 giro bike that has a 7 speed down tube shifting lever. I need to adjust the tension on the front derailer but can not see how to adjust the tension on the LHS friction shifter. The bike has been sent out with the service instructions for a SL-SY20 but it does not appear to have any information other than a parts breakdown. The fixing bolt is either over tightened or has a plastic cover which needs to be removed to expose the bolt. I am reluctant to force anything so can you please advise on how to adjust the LHS shifter on this bike?

[DaveM]

The bolt or screw that holds the left shifter on needs to be tightened a little. Tighten it enough so the shifter can still move, but it will stay in place when you let go.