Hobbes,
This crash wasn't due to a single error as far as I can see. Other people have mentioned some of the factors. I'll list the ones I think contributed and give you a little more information about some of them.
- Being the first lap, your tires were cool. By turn 4, you were making your third right turn.
- You're correct that you were on the throttle while adding lean angle.
- If you freeze the video right at the moment your front starts to slide, you will see a scratch on the pavement right where your bike is going to end up.
On point
#1 above, the tires were not as sticky as they would be later in the session. Q3's aren't bad when cold, but like all other tires, they're a lot stickier when hot.
On
#2, you'll often hear that it's a bad idea to roll on the gas while adding lean angle. We don't often talk about why. The relationship between throttle and lean angle change is important and if you could change one thing for a different outcome it would be when you began rolling on in relation to turning the bike.
Much more often than not, if people crash because of rolling on while steering, they lose the rear. Prior to switching to BMW S1000RR's, the Superbike School statistics showed that 45% of crashes we saw at the school were caused by spinning up the rear when the rider added throttle and lean angle at the same time.
Where it can be a problem at the front is in a bumpy corner. During cornering, the steering is part of the suspension. With the bike leaned over, the front wheel maintains best contact with the ground if it is able to wiggle back and forth to let the front wheel follow the bump contours. When we apply pressure to the bars, we are interfering with the front wheel's ability to track bumps. Off the throttle, there is enough weight on the front to force the wheel to follow the bumps to some extent. When on the gas, we take some of the weight away and the front end is more prone to skipping off the bumps. If we are pressing on the bars, we may cause the front to cock a little sideways at the top of a bump and begin to slide.
Also, note that it takes more bar force to steer the bike while on the gas than when you're off the gas. This not only makes the bike harder to point, it also worsens the problem I describe above. We would be more apt to upset the front over bumps because we are pressing harder on the bars.
The correct sequence for steering and rolling on is: Set the lean angle, make sure the bike is on line, then begin rolling on as soon as possible after that.
Note that while in the corner, rolling on the gas not only takes weight off the front, it also takes away some cornering load. Under acceleration, the bike wants to wheelie. When leaned over, that "wheelie" isn't vertical; it's both up and to the inside of the cornering arc. Had you completed the steering prior to rolling on the gas, you would likely have been fine rolling on the gas in that same location.
On point
#3, the line you were on may not have been ideal, but it should have allowed you to get through the corner with acceptable throttle control. It is interesting to see that someone else had crashed in the same location very recently before you did. It may or may not indicate a problem with the surface in that spot. It could have been an especially bumpy part of the corner, or the previous crasher may have left something slippery on the track surface that wasn't evident.
.
