Proper seized ... !

Ok so my engine seized at about 90mph yesterday. Fortunately i managed to stay on so it couldve been worse. Anyway, im just gonna give a brief description of what happened and anything i think may be relevant to see if i've done anything wrong. If i have i need to know so i dont do it again. Also if you want to throw a vague diagnosis please do, i know its gonna be a shot in the dark having not seen the bike or heard it etc but i just want an idea of what will/may need replacing,costs,timescales etc

Ok, FS650 on a '53 plate (newer engine, 2 wires out of right hand cover)
I use Motul 300V 5w/40 oil, changed the oil every 3 hours. I use 97 RON fuel

i bought the bike mid October 2008 with 2511 miles on it and 66.8 hours
changed oil and filter when i got it. Everything ok.

28 dec 08: 2619m / 70.2 hours changed oil
17 mar 09: 2731m / 73.2 hours changed oil
seized at 2750m / 73.9 hours

Bike sat through winter (dec-end feb) on 70.2 hours. Took it out for a good ride early march and it ran like a good 'un. carb still a little out [revving itself when pulling up to junction etc and popping quite a lot on decel] but did a 2 hour ride and parked it up. few days ago nice weather arrived so i took it out down a local backroad consisting of quite a few open straights with humps etc and a few twisty bits, i did this 2 days on the trot straight after work. then it got to yesterday (seize day) i took it out for a short run and then it was due an oil change so i changed the oil as normal (no filter change as yet) . The oil was nearly as-new. not very dark and very few bits on the drain plug. I also decided to try and sort out the revving problem i was having. now on 2731 miles and 73.2 hours. after changing the oil i started the bike up and ran it for a minute and turned it off. i let the oil settle and checked the level. it was pretty much spot on. I screwed the mixture screw in about a 1/4 turn and then i set off and rode steady for a few miles then got to the backroad and rode to the far end. bike felt quicker and throttle response a bit better but had one or two little hesitations mid corner going from off throttle to on so i screwed the mixture 1/8th back out and set off home. Bike felt a bit better than both previous settings but i felt the vibes a bit more through my feet at low speeds but a lot less when upto speed (80mph). so i adjusted mixture about a 1/16 of a turn back in. i then checked the oil level again. As far as i understood it, the oil level should be at the bottom of the sight glass when cold, and middle of the sight glass when hot ?? so i looked and it was a bit below the middle so i put a bit in (40ml-ish), gave it a quick check over make sure there wasnt anything hanging off or loose then set off again. From my house to the backroad is about 2 miles which i ride sensibly, from the start of the backroad to where it failed is about 2 miles.
I pulled out of a crossroads onto a long straight and accelerated hard up into 6th gear and at about 85-90mph for a split second it felt like it'd run out of fuel then the back wheel locked solid. Snaked for a decent distance then realised i should pull the clutch in, i then coasted to a stop and had a smoke. I tapped it down into neutral, let clutch out and it freewheels so im ok to push it home. tried to press down on the kickstarter and its just solid. pushed it home and took the engine out. This is where im upto now. The outside of the engine is just the same, no leaks, no loss of either oil or coolant. It was about 8 degrees c yesterday and sunny and dry. Radiator was hot to the touch but in my opinion not overly hot. everything else fine, rear tyre is a bit scratched. dropped the oil and the plug has small-medium size silver bits in. screen has nothing on it and the filter looks to be relatively clean (tiny tiny particles in oil sat in filter housing.
Theres a few things that i did yesterday which could have led to my problem but i havent a clue what could have done it. Ive got a feeling i killed her though but maybe i didnt ? the more i look at it the more i think that extra bit of oil did it, but i cant understand why it would ? could it have overheated ? or did my adjusting the carb do something ? could it all just be a crazy coincidence ?
The engine will be rebuilt by someone/anyone who knows what theyre doing aka NOT ME. Any recommendations of stuff to install/upgrade whilst the engine is open
thanks in advance for any help/advice/comments

Im gonna take clutch cover off before it goes to Daves but wouldnt the clutch be jammed if it was in that area ?

So you dont think my adding some cool oil to a warm engine would have caused this ?

Im going to ask Dave to keep all the old bits so i can have a look myself and il put some snaps up for all to see ...

thanks so far ...

Yeh with clutch pulled it was fine so id guessed g/box and clutch may be ok. Removed clutch cover and everything looks normal. All normal under stator cover too. Took it down there today and Andy had a go at turning it, asked me what happened and just said 'yeh thats properly seized!'
Just keeping fingers crossed. Gonna ring tomoz and tell them to keep all the bits. Was gonna go over during week and watch him for a bit but im on days so i cant now
Pi44es me off because im so meticulous about amounts/torques etc etc then it goes and repays me like this !! Hoping its one thing thats failed and jammed everything up solid stopping further damage ...

Taff if it is a blocked feed im jinxed, duc 748 failed i think due to a blocked crank oil way. big end went on that but didnt seize just lost oil pressure.

why do we do it ....

heya freaky, no i didnt notice any abnormal noises and im REALLY paranoid about noises. It felt a bit more 'vibey' than i remember it being through the pegs but i noticed that maybe 10 miles previous to the seizure and put it down to my carb settings i was adjusting. Also whilst riding i did have a listen to the left hand side of the engine as it sounded noisey but i remember it was like that last year when i rode it and thought they all sounded like bolts in a washing machine.
Coolant level was fine (i checked that after my first run out, visible through top of rad but not filled to the brim). Wasnt doing much sitting around for it to get hot tbh, 8 degrees outside and minimal traffic.
I got hold of the .... flywheel i think (rhs cover) and tried to wiggle but its solid as a rock so guessing not mains ?
Ive prepared myself for a big bill whichever way it goes, ah well there go my savings ....
Anything i should upgrade before it goes back together ? Valve springs ? t-chain ?
thanks for comments

I cant afford pockets lol !! Its cr*p aint it, my bikes are the only things i enjoy anymore, so expensive drinking, going out etc etc

the engines in careful hands now, its just a matter of waiting to see what they find and then taking it from there. Want to make it reliable if poss but that normally doesnt include making it faster haha.

oooh the suspense !

Spark plug is perfect ! Looks like it WAS running nice ...
I was going to have a peak down the spark plug hole but the lamp in my torch was blown
I dunno if anything would be visible from under the rocker covers or whatever you call them but i looked in there and everything seemed ok ...

Yeh i meant valve inspection covers lol.

Ok so quick update, daves stripped it and says its seized the mains and the balancer but not sure which went first. Also interesting to note they arent the updated bearings so presumably the originals. Engines done 70 odd hours! Anyhow, very pleased with the turnaround, i only dropped it off saturday mid afternoon so thumbs up to the DCR boys.
Once i get it back il post pics of damaged parts so you can have a nosey

Hey Freaky, yeh i was gonna update it but felt like a right let down as i didnt manage to get the old mains back for pictures
I did get my balancer bearing back which looked a little mullered and also i was told the balancer was a) the wrong one and b) was meshing too close to the gear it meshes with (sorry i dunno what its called)
Basically i was told either the mains went first which took out the balancer or vice versa. These were the only damaged parts in the engine, so he fitted new bearings and did the crank mod, fitted a new timing chain, gasket kit, oil filter etc.
He said the mains were the original ones .... ?!!
Anyway, 70-odd hours on her so dont think she's done too badly without a stripdown. Mustnt have been ragged previously coz as soon as i get it and get my confidence up on it she gives up in style.

Oh, another little bummer, They mustve left the oil screen plug out before they gave me it back so im gonna have to make a 25 mile round trip to retrieve it