I have been debugging an Onan DJC, 4 cylinder 12KW, air cooled diesel
generator. In chasing down a rough running engine when cold I just
heard the unmistakable hiss of a leaking exhaust valve.

I have not torn into it yet to pull the head and do valves or even to
check clearances yet. I have to do that. Anyone out there with some
experience on these engines? Are there any tricks or suprises to watch
for.

Thanks,
Bob