125-200cc engine seizure

So I was riding at top speed at the highest rpm for roughly about 2-3 minutes. Suddently when slowing down the bike died. (The clutch was already pulled in) Then the next time I started the bike, it made this terrible noise and it died on idle. The piston and cylinder was fine, but the plug was extremely black. There was also some very small metal shavings on the piston and the top. I can also now lift the conrod a little up and down. So I think the bearing has seized. Why do you think this happened? Is it bad to run 2 strokes at very high RPMs for extended periods? husqvarna sm 125

what oil you use in premix? what ratio?

I mix 2% oil. So for 10 liters gasoline, I mix 2 dl of oil.

I never trust an 2t auto-lube. Sooner or later they will crap out and the only way to know is a blown motor.

isnt it hard on a two stroke to run it hard for extended time, then close the throttle?
either way it does sound a bit hard on it but it should be able to take it..if your jetting is right i would be pretty suspect of the autolube, especially max rpm, max speed for minutes at a time. its also possible the conrod bearing is highly worn and this event finished it off..rpm is what kills rod bearings. you probably used up what little it had left.
you say you mix 2%, thats probably not enough oil for running a bike like that..

the sm comes with an auto lube pump, but are you saying you don't use the pump and mix only 2% of oil to the petrol mix? That doesn't seem enough somehow, I'd run closer 30 to 1. I think you mean '' I put in 2 Cl's, not dl's. Anyway a supremely black plug means a very rich mixture so that doesn't make sense. Have you still got the top end off the engine? Can you turn the crank around by hand with force or is it completely seized up?