Don't know if you can enter the track at stavelot, but if you can it will only be about 5 minutes by bike. You can take the bike onto the circuit, which makes it a lot faster to get to the paddock from stavelot. If you cannot enter at stavelot, you have to take the long way round, be carefull, people tend to drive like idiots there, cause it is the old track. So if you bike back at night, make sure you wear reflective clothing and make sure the lights on the bikes are in working order.