The Bukh service manual is available online from Bukh. Should help with the job. I haven't had to do it yet. But will be doing some work on my engine over the weekend

bukh.dk/upload_dir/docs/FAQ/Bukh%20ME%20-%20Data/Bukh%20ME%20-%2010-20%20ME/Bukh%2020%20ME%20-%20Manuals/Works%20shop%20manual/Work%20Shop%20Manual%20-%20BUKH%20DV%2020%20ME.pdf

I have experience with a Bukh DV10. It did not end well. The manuals do mention a puller, but they might be impossible to find. I manufactured a puller using an aluminium square section and some long bolts, so I could exert pressure by applying a spanner to the bolts. The fly wheel was really difficult to get off, even after undoing the big nut on the front. Not sure if it had some rust or if someone had used loctite on it. The flywheel also has some copper wire as an armature behind it, which was redundant in my motor because it was not connected. In any case the armature got a beating as I struggled with the flywheel by trying to lever it off. The flywheel is held on a taper with a key in a slot, so take care not do damage the key or slot. When I got the flywheel off the last time, I found the flywheel had a crack and the key and slot on the taper were damaged. The motor was damaged beyond repair.