before i say anything, thanks for sharing with us. we can all learn from that.
it is not easy to see what happened over the internet, and you don't seem to be sure anyway, but here's what came to mi mind...
when you locked the rear wheel you might have killed the motor. if you were still in gear or didn't hold the clutch down, the motor was probably braking almost as much as the rear brake was before you let it go.
if you tell me that you were holding the clutch, i can only suggest riding school (no offence... we all need it).
Thanks for sharing this. Its is great you were wearing the proper safety gear. Since I only have 17,000 miles of experience, I too, am curious to hear more experienced rider's theories. I almost put my bike down in a similar way but the pavement had sand and leaves as the culprit. I was only going 15mph up a tight corkscrew so I could stand the bike up.
i did have some thoughts and also hope that other MOridians will critique what I have to say. I just retook the MSF course. In it, my instructor was pretty adamant about not braking once in the corner unless it's impossible to avoid it. He also said that once locked, leave the rear wheel that way, since releasing it can cause a high side when the tire regains grip, which sounds like what happened.
Regardless of my years of riding, I haven't had an accident like this one (thank you, knock on wood), but have hit slick spots in turns. I stay away from the brake and pull in the clutch, since a freewheeling rear tire will give you the best traction. Nonetheless, as in everything in motorcycling, there are no hard rules. Hope this helps; glad you weren't hurt more seriously. I look forward to the thoughts of others.
Sounds like your thumb might have been broken from holding the handle bar on impacting the curb or while you were tossed down the hill. I talked to a guy who was riding a demo Moto Guzi through a twisty rode when for unknown reasons the back tire locked up & he went down. I didn't see the bike but told him to check the chain or belt & brake assembly (my front brake has locked for no reason before). While you replay the incident in your head, try & remember if the rear wheel locked up and stayed that way despite you letting off of it (caused by a mechanical problem), if you locked it up & let off of it to soon causing it to straighten & throw you off
(rider induced error), or if a slick substance like oil or sand & maybe to much lean caused it (I've leaned to aggressively on new bikes before). When cornering I slow before the turn and accelerate through it, in racing I think they call it hitting the apex or something, but accelerating propels you better through the turn. You might have had a little more speed than you thought going in, locked up the back tire, started looking at the curb/ditch and despite steering, you usually go where you are looking. I am no pro just learned a little from experience. It's rarely a mechanical problem but riders becoming complacent or yucky stuff on the roadway (like spilled diesel at the intersection by the gas station) that lead to collisions. IMHO
Had something like that happen to me in Corona, CA. In my case also, no warning, just WHAM! as I came down a steeply curved off ramp from the 91 Fwy. No flip back up, though. The cause in my case was pretty obvious, though. It was that nemesis of S. California bikers, the First Rain of the Season. In my case, the only injury was a dislocated shoulder, no great pain, but VERY noticeable when "officer friendly" (CHP) told me I couldn't leave the bike there. Duh!! At least he did most of the grunting to help pick it up.
I heard three calls on his squack box while we were discussing the situation so he didn't even take the time to check DL and registration, since there was no property damage and my injury didn't show - he had more serious problems to deal with.
The family Chiropractor is VERY good with dislocations, and made no nasty wise cracks. Got a new jacket with heavier shoulder padding, and replaced the scratched helmet visor.
I was rolling off the throttle when I lost it, but no brake. However, as I recall, both tires went out together, so deceleration had little to do with it. Speed less than 20 mph. Had I known better at the time, I'd have assumed glare ice traction and "paddled" the bike - which might have meant a cage would run me down, though.
notice I said I never saw the bike (I've never seen a Moto Guzi in person) but my rear tire has locked when my belt broke and a friend's also did when his chain messed up somehow. remember I'm not a professional m/c guru.
It's always hard to diagnose a problem without seeing the scene firsthand, but two things come to mind- both very basic. The first is something someone else already mentioned- there was probably something slick on the road that you never noticed (antifreeze, oil, etc.).
The other is that once you felt like you were losing control, you probably fixed your focus on where you were going to hit as you were sliding towards the ditch. Remember the bike will usually go where you're looking, so make it a point not to look where you don't want to go. Many times (not always) you can ride out of a problem by focusing on the road where you want to go and riding it out. Doesn't always work, and you may have done that, but most riders don't have the practice and discipline to do that under emergency conditions. Maybe you did that, and nothing could have helped. Glad you're (mostly) OK.
One question, why weren't you using your front brake? On most bikes it provides most of the stopping power and is very hard to lock up while letting your back wheel still rotate which provides most of your stability, and you wont chance killing your engine if you didnt pull in on the clutch.
Rear tire traction is the most important thing especially in a turn. Stay of the rear brake period. In my squid years I have had the rear brake locked without even realizing it! On sport bikes the majority of your braking power is the front brake, use it, learn it, love it because the rear brake will only get you into trouble. My position on this would be HIGHSIDE plain and simple. if you unhook the rear tire from to much gas or braking and your in a turn and you let off the brake or chop the throttle that = HIGHSIDE... you said you noticed the rear was sliding with the rear brake locked my guess is you let of the brake the bike abruptly hooked back up and threw you off that is why the bike and you also took different paths down the hill. Anyone? 954 RR keep the rubber side down, and the knee whatever your pleasure....
Grappelli I know that you are a smart guy and an experience rider so I will not burden you with condescending advice. If you ride enough every once in a rare (hopefully) while you are going to encounter a set of circumstances that are gonna put you on the ground. The more experienced you are the more you can forstall this (and the better your odds are of coming through it relatively unscathed) but at some point no matter how good of a rider you are something like this happens to all but the most fortunate.
The mere fact that you had the wisdom and presence of mind to be wearing a full face DOT/Snell helmet and fundtional protective clothing speaks volumes about your preparedness.
I second Sean's assessmenmt. It could have just been a bad alignment of the stars. It is very possible that the same thing would have put myself and 99% of the rest of us in the same place.
One thing though. The only place I EVER touch my rear brake on any road bike is going into turn 1 at Willow Springs and then only on my 954. I have trained myself to stay away from the rear break in panic situations. Track reflexes help here immensely but I just try to ride the slide until I feel things starting to hook back up - modulating traction with throttle rather than brake. Ashley calls this "an innate sense of traction" but I think that one can develop this sense of feel with some practice. You can practice this at very low speeds on dirt bikes and it is an incredibly useful survival skill.
3 months ago I had a similar accident. I was getting on a highway onramp. I was going a littlle too fast and reluctanlty eased on the brakes just as I hit a diesel spill. The front wheel went into a tank slapper and before I could react bucked me off like a bronco, breaking 3 ribs. Since you say your bike was sliding vertically, I can only suspect that it encountered something slippery like diesel or ice.