Sorting carb out on Ryobi 410r tiller?

I'm having a problem with my Ryobi410r tiller. Wouldn't start, diaphragm in carb knackered. Fitted a repair kit to carb (C1U) and now engine starts, but won't run with choke open. No prob if I use full choke / half choke to control engine speed. Seems like a fuel supply problem. I'm guessing it's the L/H needle valve setting - but not having much luck sorting them out. In addition, the H needle has a shorter tip than the L - is this right, or do I have a bit of needle tip stuck in the high setting seat?

Any suggestions?