I was changing my oil in my yfz450 and managed to snap the allen head screw that holds the oil filter on, in the case. What is the best way to get the bolt out.

 

Ok, don't sweat it! Based on the title, I thought you blew the engine or something.

That's a pretty easy problem to fix. If you're not comfortable using a screw/bolt extractor, take it to a mechanic. I'm sure it'll be about $50 or $75 for them to remove it.

I highly recomend having a torque wrench and a service manual. Torquing down the bolts to factory spec makes removal much easier. "Tight enough" can be the difference between a bolt that's too loose and one that snaps....