Azhar,
It does sound like it could be a little rich on the low. The best way to do the low is keep leaning it until it won't transition. Then richen it enough to get transition back. Do all adjusting once it is good and warmed up. The thing is, if it is a little too lean it will do the same thing, so that is why I say to lean it until it won't transition. That way you found the point of being too lean and have somewere to work from.