Right old struggle with this tonight. What’s the best way to do this without taking the whole system off the bike. The main problem is getting the reservoirs level to top the system up.

I had to remove it from the bike.
Sorry couldn’t be more helpful.

Fiddly pia.
I did mine yesterday as I ,ahem, damaged a caliper changing pads. 🙁
I took the reservoir &caliper off, but discovered or caused(!) a kink in the shifter cable and outer ,which wouldn’t allow it to pump ,so needed to replace that . I pushed the pistons by hand to bleed(from the “rear” of the v twin). Then put the new cable on….
There was more oil on the floor than in the bloody reservoir at the end!.
Work a treat now though.

Check corrosion of the cable first (unless you’re certain a bleed is necessary.

Well over due fluid change defiantly required judging by the colour of the fluid that came out…