Is this the small 10mm bolt that screws into the end of the crankshaft? If so, you'll have to very carefully drill down the centre of the snapped off bit and see if a screw extractor will go in. These bolts are often glued in with a thread sealant which makes removal difficult - you can soften the sealant by carefully heating things up with a gas blowtorch.
John, June 2008
