'05 GS500F Bad Noises From Engine

[StreetRossi]

Just about ran bone dry on oil yesterday after a big ride due to a leak I underestimated. On the way back I noticed a sudden and dramatic decrease in power, engine revving lower and taking longer to rev up. Managed to get it home and filled it up with oil again today. I thought I might have lost the left cylinder so I took out the left cylinder spark plug and ensured it was still sparking, noticed that there was considerably lower compression in the left cylinder (checked with thumb over the plug's hole and compared to the right cylinder). While I had the spark plug out on the left I also cranked the engine over a little and could hear a relatively quiet tapping noise. Put the spark plug back in and the attached video is the bike in its current state. Any ideas on what the noise might be?

https://www.youtube.com/watch?v=HikLg6D8TmU

[Meukowi]

oh jeez, surely i can tell it overheated, pistons expanded too much and gained too much friction due to no lubrication. And by the noise it sounds like exhaust/pressure leak, but as there were no lubrication it could be many things.. needlebearings, camchaft bearings etc. or if lucky just the headgasket is burned and leaks exhaust gases. But anyway, after driving without oil it needs a big maintenance, take the block off, check cylinders, pistons and pistonrings for damage and pistonring clearance. Hope for the best