Both our dune 150s came with stock 114 main and 34 pilot. The screw is about 1 turn out. With a uni filter and stock exhaust on my blue 150cc buggy and a port and polish to clean up the casting flaws it ran best with a 117.5 main and 34 pilot. (This was before the 183cc big bore stroker) I tried a 125 first and no power then a 122 and still poor power and a sputter at wot. Went to the 117.5 and it was on. This was the motor before it was bored and stroked.
Just this last weekend I dropped the main jet in the 183cc a12 cam ported head 11k springs uni filter and fmf muffler with a 7/8th exhaust tail pipe from the 127.5 to a 125 with good results. The air temp was 78and we are at sea level, did loose some top end rpm but over all felt better. Then I decided to change the dr2 from 9/10 to 8/10 rollers and one of the exhaust studs pulled out of the head.
Still ran it and it is on the money. Ran out of 91 octane but had 87 octane for the generator and it would start to crackle at high rpm and high load. It was the last day of our trip and wanted to feel the results.
As for jetting the 127.5 main would run great under load and accelerating but at wot for a long time it rand rough. With the 125 main it ran smoother from 1/4 to wot but a little loss of hard acceleration power.
I am trying very hard to get 100hp from a 10 hp motor. I think it is around 12hp a real 2 hp gain compared to stock.