Have a new .46 FX on my Superstar. I've ran about 5 tanks through it and have the needle valve adjusted fairly well. But, when I slide the throttle wide open, there is a delay before the RPMs will pick up and sometimes the RPMs will slightly drop before increasing. How do I adjust the engine to get this "delay" out?

The slow speed needle needs to be adjusted. Its opposite to the fuel intake turn it clockwise 1/8 turn and see if it improves,if not try the other way.
You can check the direction by pinching the fuel tube and if the rpm goes up the lean out the low end needle if it stops richen the low end needle.

My fx took about 3/4 gallon fuel before it was broke in good enough to get the stumble out of the mid range. I would run a few more tanks of fuel thru it before you adjust the low speed mixture screw. If It still stumbles after you feel it is broke in good then give it a little more fuel with the low speed mixture screw usally that will take care of it.

Yes, I'll try playing a little with the the low speed needle. Was adjusting it beofre my first flight with the engine during the break in and probably got it out of whack,

I have a OS 46 LA and mine would not idle correctly at first. Just give it a little time and it will start to come in. Mine took about 1gal. and now it is doing fine. Idles nice and smooth!!

the two brass bars in the carb throat should be about 1/16th of an inch from each other when the throttle is at HALF throttle. a friend of mine had one, and we could not get it to run right.. and i can tune just about any motor, (so i thought) but i couldnt get that one, so we took it to the lhs and the german local went to the shop and 20 seconds later handed us back the motor and said try it now, and that is the only thing he did. ( it will be the low speed needle) you need to set.

Yep. The .46 FX tends to have a very rich low speed setting out of the box.

the fx have a rich low needle out of the box, if you can try to get help of someone with experience, if no body is available go with the 1/8 turns at a time.

Played with the low end needle valve, got a fair amount of the jump out. But Like stated, I think the rest is just going to have to come with breaking in the engine mor e. Darn, looks like I have to go flying today.