My 87 cane started making what sounded like a way-rattley squeal which then got worse. Have you ever been hugged by a pregnant woman and the baby kicked you? It was kind of like that: I was riding home and the experience was like a metal (rod?) leg kicking the inside wall of the engine. I made it home several miles and there it sits.

 

Is the oil level correct? also check for some chain adjustmnet or a loose bolt on the fairing.

V's,
Luis

 

Hopefully its not anything serious like a connecting rod. Take it to someone who can listen to it. If its terminal, you might not want to start it anymore so that you dont do any permanant damage to the case. Throwing a rod is not good. Although, these engines dont have atendancy to do that. It could also be a number of other things too. Did the enginge sound or run different just before you heard the noise? How many miles on the bike? How long since a cam chain replacement?Any oil on the ground? Ccheck the drive train too, that can throw many noises your way too.

 

Sounds like a semi-seized chain - try oiling it as a first step......if it's old, replace it.....
if not, let's hope it's not a conrod gone mad[X(]