I screwed up literally. Not paying attention I removed the wrong bolt when changing the oil. The bolt on the left side of the engine has a large spring and a cylinder in it that popped out. Which way does the cylinder and spring go back in???????

 

I've done that not once but twice, and I'll probably do it the next time as well. Can't tell you from memory which way I put it back in, but the engine has survived so I must have gotten it right. Seems like I studied the ends of the plunger for a while, then it finally made sense which end went against the spring and which into the engine.