Define “great compression.” Those engines will run, albeit poorly, with less than stellar compression. Ideally, compression should be 100 or up.

That being said, odds are you did miss something in the carb cleaning and/or reassembly. Did you try adjusting the low speed needle more outward? (These engines take awhile to dial in the low speed adjustment, with some patience.) Did you use new packing for the mixture adjustment screws? Did you use a new main nozzle gasket between the upper and lower halves? Did the mixture adjustment screws turn with your finger tips before you tightened down the packing nuts? Does your low speed mixture needle have a good point on it? Is the float installed correctly and not upside down? (It is possible to do.) Did you use compressed air to blow out all passages? Does the throttle plate move freely? The side passage Crosbyman mentioned is the main low speed part of the carb. Using a WD 40 can with the red spray tube, blow into all those passages and make sure they are clear. I would take your carb apart again and check thsee things out. If it starts easily, that is a good sign that the engine is not junk.

• This reply was modified 1 year, 11 months ago by billw.
• This reply was modified 1 year, 11 months ago by billw.

Is this engine new to you?  If not, did it ever idle properly?  You mention having the carb apart, was it real dirty inside when you had it apart?  Like Bill said, I’m hoping this engine is OK internally.  You mention it starts well and performs well at full RPM, so that is encouraging.  The 90PSI compression reading is probably “OK”, compression gages are often inaccurate on engines with small crankcases like this one.    You also mention that the engine will idle with the choke partially engaged, another good sign.

So, let’s start at the beginning with the carburetor.  These engines have no lower cover, so the throttle linkage is exposed to all the elements, especially in salt water.  Has this engine seen salt water use?  If so, the carb throttle shaft may be binding/stuck, so the butterfly might not be closing fully.  The only way to properly determine this is to remove the carb and have a look in the back of the throat to make sure the butterfly and shaft move freely and has sufficient spring pressure so the butterfly closes completely on its own when the carb is off the engine.  This engine will not idle properly if the butterfly does not close completely and easily at idle.  The next thing to look at is the throttle plate/ignition cam on the mag plate to make sure it is properly adjusted, you will see that one end of the cam is slotted where the attaching screw goes through.  Did you mess with that at all?  In other words, if someone inadvertently messed with that adjustment, perhaps the cam is holding the throttle plate open slightly at idle.  Needless to say, this adjustment can only be checked with the carb installed on the engine.  There are two little scribe marks on that cam, which is where the throttle plate should just start to open.  Feel free to post pictures here, good pictures are worth much more than my words, and will help us evaluate and explain things for you.   D