If the idle is low, please read my post in Technical Reports on how to fix the Hose Clamp problem in the BV500. You should also make sure the spark plug is gapped properly (.028 - .031").
The idle adjust is accessed inside the pet warmer (storage area under the seat). There is a cover near the front with one phillips screw. Remove the cover. Turn the throttle and observe what moves. You'll see the cable turning a device over to one side. Right next to it in a counterbore is a male Torx adjustment knob. The proper socket for it is an "E4". They are hard to find, and when I got one, I had to turn it down on a lathe to get it to fit in the counterbore.
Adjust it when fully warmed up to 1440RPM +/-50RPM
I'd really check the hose clamps and plug gap first though.
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