I have a 2014 675r with nearly 40,000 miles as my primary commuter. Riding home the other day I felt a light pop and then had reduced power. It got me home and I started tearing it down. Low and behold one of the exhaust valves broke off and was disintegrated. The valve did make a couple impacts with the piston but it doesn't seem cracked. Not having my bike is killing my commute her in southern CA. So my question is just slam a valve in it and get it back on the road, tear it all the way down and replace the piston, or replace all pistons and valves.