I have the same engine (Yanmar 2GM) and have also experienced hard starting when cold. In my case, advancing the throttle when starting seems to help.
In my experience, valve clearances and injector spray pattern can both contribute to this problem. I got the clearances adjusted correctly this Fall, and I plan to replace both injector nozzles in the Spring.
BTW, I am very pleased with this little engine generally. It is well worth working on to solve the problem.
In the (unlikely) event you need a rebuild, this particular model has dry cylinder liners. To renew the cylinders, you simply replace them and install a new set of rings (or piston/ring assemblies). No boring required.
Last edited by Goodnewsboy; 12-20-2006 at 02:07 PM.