Hi, should be 5W40 for cooler temps (around or below 0 deg C) and 10W50 for warmer temps.
Fully synthetic is recommended. Your clutch will not slip as long at it is proper motorcycle oil (or "MA" qualified). MA or MA2 basically says that it is wet clutch compatible.
I run 20W50 as it is much more common that 10W50, just let the machine warm up for a bit longer.
Many people run mineral oil without issues, but as you said before, you are not too concerned with $$$, so use synthetic. It is better, but it costs more.
Again, find a balance between frequency and quality.
Lower quality oil (mineral) = more frequent changes
Higher quality oil (synth) = still frequent changes!
These engines love fresh oil. After having torn into my engine I can truly appreciate the importance of having a better oil in there and switching more often.
If it were me, I would choose a cheap oil and switch it often. If Belray is a good price, go for it. If not, then choose something else. Trouble with this forum and oil discussions is that the pricing map for Canada/US vs. Europe is completely different. Over here, Rotella is dirt cheap and Motorex costs more than gold. Perhaps over there it's the opposite.
Some decent oils from what I've read/used:
-Amsoil 20W50 (now they make a 10W50 as well $$)
-Lucas oil 20W50 ($$)
-Ipone 10W50 (from France, $$$)
-Motorex 10W50 (great quality, $$$$)
-Shell Rotella 10W40 mineral for diesel engines ($)
