Check your hall sensor and ignition connections.they can go bad and lose contact even though they are fully plugged in. I have had two hall sensor connections fail.

What is the compression like right now compared to when it did run good...like in hand propping the engine over...not using electric starter. How about cold compression verses when engine is warm? Also with the 2 different rings you tried. Thanks

Jeez, this has pretty much become a quest for you. Many would have given up long ago.

One last suggestion (about the only thing besides demonic possesion that hasn't been suggested -- maybe have some fuel blessed and hit it with 'holy-gasoline').

The original symptom of dying back on a full throttle pass, and crudded up (rich) both could be caused by partially plugged exhaust. If you store it where them XXXXXing mud wasps can get to it, I've seen them get into a muffler and build the nests (mud plugs) INSIDE the muffler.
They love 1/4-3/8 openings. Chainsaw/weedeater mufflers, compressed air and hydraulic quick connects, and bolt holes.

The case of internal muffler plugging was on my old towmotor. It became a quest too, with all the truck drivers that delivered to my shop throwing out ideas. (the OLD internet) It would run about 25-30 sec, start skipping, and stall with a backfire. It would idle fine. I finally found the problem because you could hear a hissing after it stalled - we thought it was a propane leak, but it was the built up pressure in the exhaust system bleeding off. The wasps had filled in almost all the baffle holes - this is a 1950 something machine with a CAST IRON muffler.

This is an exterme longshot, but I think you have worked your way to the freaky dept. This will be one for the record book.

If you do give eventually give up on it (even though you don't seem like the kind of fellow that wouldl), drop me a line, I'll make you an offer on it just cause I love a mystery.

I guess check the hub key if you haven't already

That's next and a good idea.
I'm going to send it out though.
I'll let someone with bigger brains battle with it.
It will be interesting to learn the root cause!

Check your hall sensor and ignition connections

Replaced the sensor in the write up from yesterday, no change.
Good idea though.

What is the compression like right now compared to when it did run good...like in hand propping the engine over...not using electric starter. How about cold compression verses when engine is warm? Also with the 2 different rings you tried

The compression seems the same, or to put it another way, I didn't noticeably feel any difference.
It always started right up.
Had a lot of blow by though.

could be caused by partially plugged exhaust.

Good thought.
I soaked it in solvent to decarbon it and the exhaust was clear.

I'll make you an offer on it just cause I love a myst

Thanks Scott!
Now that's the best thing I've heard yet.
I appreciate it, and if I don't send it out, you're the first to know!

Thanks everyone
Bob

To confirm no issues with fuel system, maybe set a jug of fuel next to it and run a line from it to the carb and see if that changes anything?

Hang in there. You'll find the problem eventually.

AHicks -->

That's what I meant, and what I did when I listed the "different fuel tank" in my litany of things done yesterday.

Thanks
Bob

I haven't noticed any info on whether you have plugged a different, known good, battery directly to the ignition. A weak (tested under a load) battery can cause weird problems.

I haven't noticed any info on whether you have plugged a different, known good, battery directly to the ignition

Post 47 shows --> Different Ignition Battery (Hooked Direct)

Thanks though
Bob

just try it with out a muffler

Very good and interesting thought.
One of my buddies just recommended the same thing.
I just took the muffler off and it's free and clear as a bell, so in other words,
no restrictions.

Unfortunately, after yesterday, the engine is off the plane and ready to ship out.
I'm a no runnin it no moe

Great idea though!

Take care
Bob

If the engine has what you call "blow by" the piston ring needs replacing & end gap needs to be small.

Ring was replaced yesterday in previous post

Instead of running around in circles, do some analysis.

Fuel - you seem to have covered most things multiple times. Except for the pump diaphragm and the metering diaphragm -
There are multiple pump diaphragms in most rebuild kits, the wrong one is easily installed. It is also possible that you have received a kit with a "pre-perished" black carb diaphragm (I prefer to use the Teflon (Tan colored) diaphragms or the Acetate (Blue colored) ones).

The Metering diaphragm is easily installed incorrectly or in the wrong order of parts (Carb, Gasket, Diaphragm, Cover - in that order). If your original carb was assembled wrong, it is possible you have assembgled the consecutive ones wrong also. Is the needle under the metering diaphragm absolutely free to move? Is the lever height correct?

Air Leaks
Instead of stuffing around making things, blowing or sucking on them etc etc - Get yourself a can of WD40 or Carb Cleaner. Install the little tube on the nozzle. Start the engine, Spray the fluid at the joints on the engine and (carefully) at the prop hub. If there is a leak, you will find it as the engine will instantly react.

Ignition
Have you got a fresh charged and good condition battery pack that is suitable voltage for the ignition?
Exactly what plug are you using? & Where did it come from?
What plug gap are you running?
Have you tried another ignition? (Including another hall sensor).

For the dying when running on the ground at full throttle - how long does this take?
Running on the ground with the plane stationary for long will cause overheating. Just because the cylinder is out in the wind on your profile (nice plane by the way - I have one also) doesn't mean it is cooling well, our props are not all that good at working as fans for cooling when the plane is stationary.

Fuel system - 2 or 3 line?, In line fuel filter or not? what are you using for hose clamps? can you see bubbles in the fuel line to the carb when the engine is running?

Except for the pump diaphragm and the metering diaphragm -

Original carb was rebuilt.
New carb exhibits the same symptoms.
All parts were installed correctly.

Have you got a fresh charged and good condition battery pack that is suitable voltage for the ignition?
Exactly what plug are you using? & Where did it come from?
What plug gap are you running?
Have you tried another ignition? (Including another hall sensor

As stated previously, the original known good plane battery was used, then another known good
battery was hooked direct.
CM6
NGK
Specified gap
As stated, another new ignition was tried.

For the dying when running on the ground at full throttle - how long does this take?

Like I said, around three seconds peak before it started to drop off

Fuel system - 2 or 3 line?, In line fuel filter or not? what are you using for hose clamps? can you see bubbles in the fuel line to the carb when the engine is running?

As stated previously, the original plane fuel system was tried, then a direct line from the carb to the
fuel jug.

Thanks
Bob

The prop isn't oversize is it?