Roy, thankyou for your response. No, the engine is not running when on the centre stand, I do however revolve the rear wheel in the direction of travel, and the chain is as far as I can tell, correctly adjusted. The way in which I adjust the chain is to check the tension with the bike off of the stand so that the weight of the bike is on the suspension. I do recognise what you are suggesting though, as whenever I have set the chain tension with the bike on the centre stand it always seems to be on the tight side. The problem is I know nothing about the workings of gearboxes, and therefore I am rather reluctant to start stripping it for examination. I really would not know what to look for. The sympton of what happens while changing between 1st and 2nd is not unlike that of the return spring being weak or having failed. I have rearsets so I have 1 down 3 up, and if I hook the pedal up after 2nd has failed to engage, it will then engage after doing this. All rather weird really.