My step-dad gave me Goldberg Ultimate with a YS 1.20 up front. (He has not flown for over two years) Anyway, the engine did not want to run properly. I took it off the plane and found the regulator ports clogged up with what was the gasket. The valve cover gasket was also terrible. Removing the backplate didn't reveal anything that "looked" bad. I cleaned the regulator and installed a new gasket. I adjusted the valves and installed a new gasket. Tested and installed a new F glow plug. After some reading I found that this engine, I believe to be a NC( it has no low end needle) needed the air hole in the carb assembly drilled out to 1/16. I did this. I still can't get it to run. It will start and idle but cuts off. If you ever get it to the top end it still seems to lack power. Go from the top end and back to idle and it will never throttle back up. Someone said to find the YS Doctors website, well it's shutdown!!!!!!

There's a couple of things to try!
First, go to Central Hobbies and get an oring set. You've started the process by replacing a couple of gaskets but you need to replace them all! Pull the regulator assy and check the diaphram for tears or pinholes. If you want to do it right then by one of these also and replace it.
Pull the cam cover(right side of engine), pull the top rocker arm cover and remove the right(exhaust) pushrod. Go back to the cam and push the lifter up so its out of the way. Put the piston at tdc and check that the dot on the cam gear is straight up!

You can do this when you are replacing the o rings because you are gointg to have to pull the head to replace the push rod cover orings. Remember to replace ALL the orings. Teh motor should perk right up!

DDog- I have been at this morning. I did some plumbing work and replaced a fueler valve with a brass T. I believe the valve was bad and adding to my problem. I ran the engine a few minutes ago. IT RUNS. Top end is Ok. Idle is not. It seems to load up and want to die. Add throttle and it is SLOW to return to max power. Regulator problem maybe??? There is no low end adjustment for this engine.

That is correct! On most of the YS motors the regulator controlled the low end and mid range. The newer motors have a low end adjustment also.
Make sure you have the fuel and pressure nipples plumbed correctly. After running at half throttle you should shut down and if you disconnect the pressure side of the tank, you shoul get a very audible hiss of pressure release.
Start with the regulator screw flush with the housing and hi end needle about 2 1/2 turns out. bring up to full throttle and adjust for max rpm. Bring to idle and check transition. If slow then turn brass screw in about an 1/8th at a time until you get smooth transition. Always readjust the top end after each low end adjustment.
You should contemplate changing out those Orings! It will help.