Have a Walbro WA167 carb on an older Zenoah G23. Adjusting the low speed needle has no effect. Can turn it all the way in or several turns out with very little or no effect. The screen is clean and the plumbing good with no leaks. Any ideas ? Low speed jet mabey plugged ?

Not likely, but possible...The little holes are under a welch plug that is destroyed when you remove it...I probably have a few here if you want to check out the holes...the plug is thin aluminum...Walbro makes a removal tool, a 1/8 wide flat blade that is CAREFULLY stuck through the plug at an angle, then just popped out...It's possible to hit the holes if not done with care...Check the setting of the inlet needle lever, it should be flush with the casting next to it, not the top surface of the carb body....
I have seen only 1 carb with the holes plugged in 18 years of looking at Walbros....
Maybe take both needles out and shoot some Wal Mart Super Tech brand carb cleaner through the holes...$.87 for a big can, it works great, not environmentally friendly
I buy it by the 8 can case, use it for cleaning off everything....It dissolves some plastics...