I posted this on RCG, but I know not everyone frequents both sites.

I ran my freshened up YS 61AR today. It has new bearings, new gaskets, new regulator, but not new orings.
First what plug should I be running? I have a OS 8 in there now. The pipe is set at 17.5" to the first disc. It is a Hatori pipe, but not sure which model number. I ran 5% nitro and also 25%, both with 20% oil. The needle is not overly sensitive, and it does not get hot which tells me the pipe is close.
The problem is that the needle is very inconsistent. It will run fine at 9800 on a 13x10 DW prop, then all of a sudden it will go rich. It will quit if I let it. I have to pinch the fuel line to clean it out. If lean the needle, it will clear out, but then be too lean. Back the needle out, then it goes back rich and will not clear.
It idles fairly well, but does load up a bit. I turned the regulator in about 1/2 turn total from flush and that helped, but much more seems excessive. The fuel system is tight and leak free. It will hold pressure for as long as you want it to, and it builds pressure very quickly.
I have run YS 4 strokes for 20 years, but this AR is totally different.
The basic questions are:
what fuel, plug, and prop are the standards?
What should I look for with regards to the wierd needle behavior?

thanks
Jeff