The simple theoretical limit is 1.0G and occurs with the bike at a 45-deg lean angle. It assumes the tire's coefficient of friction with the ground is 1. It's the same for all bikes, even Harleys. It's also 1.0G for cars.
In reality, things get a lot more complicated. Super sticky tires can interlock with the pavement and have coefficients of friction higher than one and in this case, you can go over 45-deg and corner at somewhat more than 1.0G. OTOH, pavement isn't perfect and there are other loads on the tire which reduce maximum cornering G's. So the answer is that "it depends".
Regardless, the maximum cornering G IS limited by the tire's traction. The reason F1 cars can develop in excess of 5G of cornering load is because they have wings that push the tires into the ground letting them develop huge amounts of traction. If you could have the same on a bike, you could corner way over 1G, but putting aero downforce on a leaning bike is obviously fraught with problems.
Hanging off affects the bike's hardware lean angle, but not the lean angle of the combined bike/rider mass. It's a method of having the rider closer to the ground so that the bike can be less close and have more clearance between parts that might drag. But the overall lean angle of the bike/rider system is not changed by hanging off.
Last edited by markjenn; 11-22-2012 at 01:31 AM.