I have a pretty old Varadero. It's a 125cc twin-carb v-twin.
I open the choke to start it, it starts first time, warms up slowly (10-15 mins), then when I push the choke in, the idling doesn't really settle, it fluctuates.
I ride it for about half an hour, and the idling still fluctuates at ~2000rpm by about +/- 200rpm. If I then don't rev it and I leave it idle, after about 20 seconds, the idle will slowly drop and it will cut out. When it's cold, it doesn't seem to cut out and it seems to idle better.
What could be causing this behaviour? Is there anything in the carbs that may need to be replaced? Is it a mixture problem? Do the carbs need to be balanced?
Are there any simple tests I can do to narrow down the possible causes?