Good Afternoon (edit it's not morning any more, where has the day gone?)
....to drop onto the 11t it is a bit temperamental and only moving across first time on about half the shifts, would I be right to think i could try and wind the H screw counter clockwise a little bit?
It sounds like you've followed the setup steps of select 5th, enter setup mode and "change down" until there is a slight rub on 4th sprocket and then "change up" 4 times.
If you have done this and you can't get the smallest sprocket reliably then looking at the limit screw (stopper bolts according to the Shimano docs!) seems quite reasonable, especially if your micro adjustments have moved the cage 1 or 2 stops outwards whilst still in 5th gear.
This is where Di2 and mechanical do differ, you mustn't undo the limit screw a lot, go onto the smallest sprocket and then adjust the limit screw so that it just touches the limit plate.
It may be non obvious but on upshifts the rear mech deliberately overshoots, waits for a bit (<1 second) and then downshifts by something like 1/5th of a whole shift. You need to allow for this overshoot when adjusting the limit screw, Shimano say undo the limit screw one complete turn.
See the caveat below.
No no no. Get someone with Di2 knowledge. It needs a bit of tinkering but you need to know what you're doing. Shifts should be seamless and quiet.
I have an older 10sp Ultegra Di2, read the manual and treat it like any mechanical system apart for the overshoot, am I missing something and am about to break it?
I sometimes get a "Campag style" solid reassuring kerchunk shift and a good proper gear change when going from 3rd the 4th, 21t to 19t. This pure speculation but I suspect that this might be a point where I change harder underload, as 50x21 is quite a low gear I may be in it going up a slight but long hill and am now going downhill, spun out and already in a high, for me, cadence even after the shift.
This change is also the first change where there is an overshoot and correction.
Bye
Ian
