Dip tube is the tube in the
fuel tank that pulls
fuel from the bottom. As the
engine starts easy when warm, probably not that.
A small vacuum leak in the
fuel system can cause the same starting issues as bad rings. Hard to start at first, easy after first time.
BTW
yanmar lists moving the throttle forward a bit when first starting. I generally only need this on a cool/ cold day. The GM being a strict
compression engine (no glow plugs), well it can be a tad cold blooded first thing on a cool day
If there is no sound difference on the decompression levels and there is no venting of air / smoke from the
oil fill hole when running, then
compression is good.
IF you do get a venting noice and smoke out the
oil fill, then you have excessive blowby. Normally caused by bad / broken rings. With a
yanmar GM engine ring wear would not normally fall outside new tolorances with 1100 hours on it. So a low hour engine with bad compression would need R&R ing.
If you do have bad rings, you can read about how to
rebuild a yanmar gm here with my summer of discontent, back in 2013:
http://www.cruisersforum.com/forums/...ar-107705.html