On Thu, 22 Apr 2010 21:04:25 -0700 (PDT), Frogwatch
wrote:

I've never been able to hand crank my diesel, either the 6.5 hp nor
the 13 hp even by releasing the compression.

Is it a Yanmar? If so they have much smaller/lighter fly wheels than
the old Volvo engines, and don't have enough angular momentum to carry
the piston through a compression stroke after you close the valve.