But the large sprocket runs at half speed!
Advanced timing is good Matt - as the chain wears in and stretches it will fall back slightly. If it was mine - I would be leaving it as is.
A simple way to find true TDC is to screw a bolt into no1 plughole (I knocked the centre out of an old sparkplug & stuck a bolt through that)then turn the crank slowly until the piston touches the bolt mark the pully inline with the pointer then turn crank the other way until it touches the bolt again mark the pully and the point halfway between the two marks will be TDC.
They keep on stretching! And whose to say your 'advanced' timing isn't ideal for your engine/use anyway ? Unless you compare on RR or with hill climbing trials you really won't know. How do the valves look on overlap at TDC - is there much difference in the lift of the two valves ?
Maybe - but then maybe he's just quoting the standard figures. If you really feel you need to move it - then offset key is the way, as I'm sure you know. But it really is a tiny tiny amount that it gets moved - and it's a load of work to do it. And when I did this some time ago (on 1340 Mini) I certainly couldn't detect any difference in the engine whatsoever! All I can say is that - in my experience - advanced cam is a whole better than retarded cam! I urge you to compare the valve lifts at overlap - you may get a pleasant surprise.