A bad day for my bike

The two of you who read this blog probably know that I have a job in Annapolis and commute home to DE on weekends. Last Sunday I rode home to join the family for our boy's high school graduation party. In preparation for that trip, by the way, I had visited Bob's BMW and gotten an oil change and a new back tire.  You might recall that I had the clutch replaced a month or two back, so the bike was in pretty good shape. I thought.

About 25 miles from the house, tooling north on I-95, the bike suddenly lost power. I headed for the shoulder, thinking something electrical must have happened, but the bike kept running, and except for the loss of power, it sounded okay, so I figured the closer I got to the house, the better, so I kept going. I got all the way home. Later, after the bike cooled down,  I poked around, checked the oil, and couldn't see anything bad. I started the bike. Still ran weakly, but the exhaust felt the same on both sides. I called my buddy, Davis. He asked a couple questions  took note of my mention that I could detect a little oil at the end of the right exhaust. He said pull the right spark plug, so I did. Ordinarily, when you unscrew a spark plug, once you crack it loose, it's easy to unscrew. Not this one. I was afraid it had been cross-threaded. That wasn't the case. Here's what the end of the plug looked like:

I still have this in my pocket, as a souvenir. Ask and I'll show it to you.

My bike had run smoothly, if weakly, for 25 miles on one cylinder. It was too late to attempt further diagnosis, and I had to get back to Annapolis, so I borrowed a spare bike from Davis. When he saw the plug, he expressed his astonishment several different ways, none of which are repeatable in this family-friendly blog.

Today Davis and I took off the right cylinder. This is a fairly easy thing to do on these old BMWs. Here's what the inside of the head looks like: 

The mechanically inclined among you will notice immediately that the exhaust valve is missing, and the surface has been battered. 

Here's a view of the top of the piston:

Obviously something banged around in there a bit, and at about ten o'clock you can see the blackness of a hole punched clear through the poor piston. 

The valve itself was nowhere to be found. The sides of the cylinder appear undamaged.  Near as we can figure, the valve managed to escape through the exhaust port and it's resting somewhere in the exhaust header or muffler. 

sigh. Anybody interested in a parts bike? Except for the right cylinder, it's in pretty good shape. Oh. I'm in the market for a BMW K series with a full fairing.