truckernix: The first clue should have been that the pistons were hitting the spark plug when I first started the motor up and it was missing. I pulled the plugs and found that the gap had closed up on a couple of them. Being new to these old inlines it didn't click. Someone had a post on anouther site that there was no way the piston can hit the plug, that started me looking into this a little deep and with breaking rocker arm shafts. The piston is domed and the dome was put together on the wrong side because now that is the way a domed piston is away from the valves and closer to the plug.
No the motor wasn't really noisy. It gave me no sign that I had any problem. It started up and ran fine. I do think it had something to do with a higher rpm because I had drove it around town for a few days both times before the rocker shaft broke. They didn't break until I took it out of town and running it at a higher rpm.
The motor is at the machine shop.
