I use the general rule of thumb of 1:2 ratio between running and biking.
The short answer is yes... with proper diet you'll be fine at your current weight and probably loose weight.
However, I like to stress that anyone from a running background take it easy the first couple of times on a bike. Runners have the tendency to try to get a workout out of everything. Biking is a different animal. Don't worry about speed or pace. You can blow yourself if you try to go on a 3-4 hour ride with the 'feel the burn' mentality. Keep your gears in something manageable. Gearing: you should set up in your 39 sprocket up front (i'm assuming you have a road bike) and 16/15 in the rear.
So, start off with an hour bike ride and make sure you feel refreshed and comfortable on the bike at the end of it. Nice easy pace. Don't worry about your speed or heartrate.
Once you feel comfortable on the bike. Monitor yourself via a heart rate monitor. Stick your heart rate between 120-140 and do that for 2-3 hours. It may feel as if you are not doing much. You'll be fine.
As an aside to runners out there. The single most common trait of a runner starting out as a cyclist is the inability to utilize smaller gears. They feel like to get a workout, that is they push a very hard gear to 'feel something'. This is generally not beneficial. You will feel like dirt and your legs will be shot for the next day or two.
Remember nice and easy. save your legs for running
-lhd