1. Decreasing-radius corners can get tricky for the simple reason that if you approach the corner as if it were a constant radius, you won't have anything in reserve when the corner tightens up. The trickiness is compounded when the decreasing-radius corner is also blind, as they often are.
A good rule to go by to ensure your safety margin is this: Never go into a corner at a speed without a "reserve" that allows you to correct for something unexpected mid-corner, whether it be debris in the road, negative camber or a decreasing turn radius.
The rider in the first photo is approaching this decreasing-radius corner on the outside edge of his lane, since doing so provides a better look through the oncoming corner and a better angle of attack should it tighten up. Regardless of the corner, make sure you don't get in too hot.
2. We always say to look through the turn and down the road, and this case is no exception. If you're on an unfamiliar road, then looking well through the corner will alert you to the decreasing radius before it's too late to react. Avoid using an early apex since you'll then be drifting to the outside of the pavement just as the radius starts to decrease. Not an ideal situation. Release the brakes before you turn the motorcycle, then crack the throttle to unload the front end as soon as possible. You'd be amazed at what a difference early throttle application makes in the willingness of the bike to arc through the corner. In this photo, the rider is off the brakes and starting his throttle input, even though he is only a third of the way through the corner.
3. The rear brake can be used to slow the bike slightly and tighten the cornering radius of the motorcycle, but first get used to the sensitivity of the rear brake so as not to lock it up. Don't slam the throttle shut in the middle of a corner as overloading the front end could cause it to wash out. As the corner tightens, simply dial in more lean angle, which shouldn't be a problem since you left some in reserve, right?
4. A large number of crashes occur when riders panic and stand the bike up, when in fact a corner can usually be taken much quicker than most people think. At the late apex of a decreasing-radius corner, you'll be nearing the inside edge of your lane, so let the bike drift out naturally to the middle of your lane and drive it out of the corner, making sure to stay well clear of the center line of the road.
On a road you don't know, it's important to ride with reserve. If you enter a corner at full lean angle and then suddenly realize it's beginning to tighten up, it'll be too late to correct. Get into each corner knowing that no matter how tight it gets, you'll be able to compensate accordingly. And make it to the next corner to do it all again. SR