Weak links in the four-valve BMW GS Boxer Twin are the cylinder heads, which have valve covers secured by just two bolts. The covers are prone to damage if they hit something, which can cause the cover to rotate and dislodge the gasket. AltRider's (www.altrider.com) 1-inch stainless-steel crashbars (silver, $424; black or white, $436) wrap around the head. AltRider's 4.75mm-thick, heavy-duty anodized aluminum skidplate (black or silver, $286) protects the engine, exhaust headers and cross pipe, and the oil filter. Handguards on any bike as big and heavy as these need to be tough, which is why we recommend an aluminum-reinforced type like Barkbusters' VPS ($155) available from Twisted Throttle (www.twistedthrottle.com). Put them on your KTM ($96) or Yamaha ($155), too.