Engine will idle and run full throttle fine, but the transition from idle to full is the problem. When rapidly increasing throttle from idle to full, the engine wants to die. I've tried opening and closing the low end niddle by 1/16 turn with no success. I started st the factory reccomendations for the needle setting both times. If the throtle is increased slower it does fine.

What do I need to try next?

It's all about the needle settings. Starting with the high end needle, peak the engine for max rpm and then back off 1/8 turn. Drop the rpm down to about 2500 to 3000 and tweak the low end needle for max rpm and see what happens. Go back to the high end needle and check it again, it probably changed a little. Now go back to the low and re-peak. You should then be close and only 1/16 turns should be needed to get the low end needle right. The top should not need to be changed again.

Make sure the engine is very secure and keep your hand out of the prop!!!!!!!!!!! You need a 1" or less screw driver blade to do it this way.

[b]Disclaimer. [/b] A spinning propeller can be, and has been, extremely dangereous and can do severe harm to the human anatomy. Extreme caution should always be used when attempting to adjust or perform work on a running engine with a spinning propeller to prevent death or injury. The safety of the individual working on the engine is the responsibility of that individual.

The oil mix should be between 70 and 80-1 using a good synthetic. Plug fouling will occur at mixes under 65 to 1

Not much room between the needles and the prop on this motor! Especially at full throttle! [X(]
For adjusting these, might I recommend the following little tool. [link=http://bennettbuilt.com/page10.htm][LINK][/link]
Took me about an hour to knock off a couple from dowel and brass tubing in my shop.

What do you mean, 1/16th from recommended settings?
If the engine idles fine, but fails to respond well to throttle application, idle is too lean. Open up 1/16th turn at a time, until trottle response is ok, even after prolonged idle. In between, always reset the main needle to max rpm, and open up the main needle to the point that the engine just starts to loose rpm. Remember: Main needle and idle needle work together to provide full bore mixture. Final tuning of the high end is to be done by judging the spark plug. The central electrode isolator should be a doe tan, or light gray, depending on oil and gas used.
The walbro carbs do not have the usual acceleration pump that automotive engine carbs have, so try to resist the urge to quickly jam the throttle fully open. Instead, <apply> throttle in a way that the engine can follow. It is a relatively fast sweeping stick motion, just like operating the accelerating pedal in your car, which allows the carb internal fuel flow to pick up speed while you apply the throttle. Some transmitters have the option to reduce servo speed. Use it if available, or use a rather slow servo instead for throttle. The prop needs to spin up as well.
Resist the urge to lubricate too little. Follow the manufacturers recommendations. Some synthetic oils cannot be mixed below 1:50, I like 1:35, so I will not use these oils. (I use Mobil 1 2T racing or Valvoline Synpower)
Plug fouling stems from wrong carb adjustments or wrong plug type, not oil content. Too little oil will cause the engine to run slower and wear faster.
Good luck.

Is it a good thing to have a little soft carbon in an engine or should it always be squeeky clean after many flights or long use?

To be honest, I don't know for sure.

Throughout the past century, engines have been running and living with carbon built up.
Small carbon particles filled up all machining grooves, and kept some lubricant in there to help in bad times.
Being an old farth, I know these engines ran very well indeed, though cleaning every now and then was required.
During these cleanups, one had a chance to check on the piston, ring and cylinder, and cylinderwear near the top of the stroke was quite pronounced.

Some of the new synthetic racing oils that exceed JASO TC class, leave the engine spotlessly clean after hours and hours of running. This is needed for the variable exhaust timing valves in competition engines, that would otherwise stick, and fail to function, being choked with carbon. The spinoff is a clean engine throughout, or a little bit very soft carbon build. The oil has lots of detergents and high pressure additives that seems to avoid or even prevent film breakdown by high ring pressures and roller bearing scuffing. On checkup time, less wear is visible, especially near the top of the stroke, and needle bearing running surfaces show a light tan (patina), without measurable wear.
Looking at all that clean bare metal inside, I sort of miss the thin carbon layer, that gave me so much proof of a well run engine. With the new oils, even guessing how long the engine has been run is a tricky task.

If a little soft carbon will worsen this condition?? Peronally I don't think so, though like stated, I am not sure.

Long ago when I worked in the Chain saw industry it was rare that a saw piston did not contain some carbon. Back then we didn't recommend synth oils and this was a contributer to the carbon deposits. The measurable loss do to the carbon was Nil in my opinion. We did have a generator that would develope excessive carbon and the result was that it would Deisel and not turn off. The Chain saw guys would put a lot more hours on their saws that we do on our planes for the most part so I doubt you will see too much carbon. Just my .02.

If nothing else works, it might be time to rebuild the carb. Brand new metering and pump diaphragms, plus a squeaky clean internal carb fuel screen make a lot of difference.

Thanks for your thoughts.
I have always wondered this.
Some people state that the cleaner the better.
For me, I don't think I have ever seen an engine without some carbon.
While this does not make it right, it does make me comfortable.

A little carbon doesn't hurt a thing.

Now not once did I ever say "recommended setting" The correct needle settings for ANY engine will be determined by altitude, climate conditions, propeller choice, and oil content. There is NO SUCH THING as a correct setting for all engine types. Anybody that believes so has got their head up somewhere it can be hard to locate.

Nor am I going to tell someone that their engine is too rich or too lean. The engine owner needs to learn how to make some determinations by him/herself, and not completey rely on someone else to do it for them. The basic understanding of rich and lean should be reasonably understood by the time someone moves up to a gasser. Glow or gas, rich or lean is the same. Only the adjustment process should need to be explained by this point.

BTW, if I change nothing else on an engine other than the oil mix, I can, will, and have fouled plugs, OFTEN! Sorry for one of you in particular, but I go with reality, not theory and published script. As I've stated before, I'm not an engineer or an architect that relys on what should work based upon long and tedious calculations, but a person that goes by what actually works in real world practice.

As a footnote, changing the oil ratio will often require that the needle settings be changed to reflect the higher or lower oil content. The amount of oil used will change the flashpoint of the mixture. We only have a very limited number of plug heat ranges that will work with our engines and still maintain a resistor value, so we have to work with what we have available. Those that are using an engine/plug combination that don't have a "resistor" counterpart have a much more limited choice.