Small Engines (Lawn Mowers, etc.): Sears Tecumseh 4.5hp carb problem, mineral spirits, fuel intake

Question
Hi,  Thanks for your help in advance!

I have several Sears, push lawnmowers with 4.5hp +/- (Tecumseh motor, no needle adjustment).  Good compression, checked and cleaned plug, good spark. Cleaned the carb, and replaced parts, (needle, seat, gasket, cleaned all passages, checked float and adjusted, ultrasonically cleaned carb, replaced air filter, manifold and carb gaskets, soaked in carb cleaner, emptied and cleaned gas tank, put in fresh fuel.  Ten times over!

Prime the bulb (min 5 times), pull the cord and the engine starts, sputters, runs for 5 to 10 seconds and dies.  Repeat the process and maybe starts again, with some gas in the cylinder head or carb cleaner in the air filter intake.

I have had the carbs on and off the machine(s) at least 10 times, nothing left to clean, spotless and compressed air passes through all of the orifices.  The only thing I have not done is remove the welch plug or soak it in caustic carb cleaner.  If I do this, I understand I need to remove the rubber parts, how about the plastic fuel intake elbow?

I know Ethanol sucks, but this is ridiculous.

I am ready to shoot the thing(s), blow them up, or crush them with my excavator (diesel - no problems) to take it out of "MY misery".  My Honda's start on one pull every time, so do the Briggss.  What goes with Tecumseh?

Thanks, Ray

Can you help?

Answer
I don't bother rebuilding them as we only have a 50% success rate, I just replace them.  Most of these are pretty cheap, though availability is getting less and less since Tecumseh shut the doors.

Personally, I think you've spent enough time trying to fix a carb that corrodes way too easily, which is probably causing your headaches.  But, if you want to soak them, the fuel intake elbow won't be eaten off by commercial carb cleaners or mineral spirits.  It's more likely to break them when trying to pull them off than the cleaner harming them.

As an aside, I switched to ultra-sonic cleaning about 8 months ago and have found it far superior to the commercial carb cleaners.  I use white distilled vinegar and distilled water in a 50/50 mix with a healthy dose of Dawn Ultra dishwashing detergent.  Then rinse with warm distilled water with baking soda added and then again with plain distilled water heated to just below boiling.  This concoction will clean most anything, and if it won't, then we scrap the carb.