I have recently purchased a QJ Supershadow 250 for joy riding. However the past two rides have proved somewhat stressful because after getting to my destination, on my return the bike starts ok but then stalls when I stop and it seems to jerk slightly when moving. I am thinking that perhaps I am not setting the fuel tap correctly. The key has an arrow on it. On top there is a picture of what looks like a test tube half filled, on the bottom a full filled test tube and on the left (facing the tap) the writing PRI. When I start my ride, I point the arrow down to the full filled test tube. Am I doing it right? Alternatively I also noticed that the trottle cable is not secured tight to the box under the trottle handle. Could this be the problem? Any help would be appreciated. Thanks