Kawasaki Vulcan 800 Clic Twisted off piston bolt?

I was tightening the bolt on the backside of the front cylinder housing and I tightened it too tight and the bolt twisted off with part of the treads. I do not know what this part is called and I need to know. I've looked at all the schematics and it doesn't name this part. There is a about a 3" long by 3/8" diameter spring on the inside that came out with the bolt. I was wondering if this is very bad and what the part is called.