RE: DL-50 engine
Here is a copy and paste of a post by Pe it is a very well written set of instructions on how to tune your engine properly...
The balancing act between low and high needle seems to be the most difficult thing about gas engines with floatless carbs.
There is a simple rule about this.
If the engine is easy to start, the low probably still is too rich. Lean out the low until starting without choke in a warm engine becomes impossible. That is the "too-lean" setting. From there, open up, but no more than 1/4 turn.
Other method according to Walbro instructions:
At slightly high idle (about 1800 rpm), find the L-needle setting with best rpm, by finding the lean rpm drop and the rich rpm drop. Best setting is in between.
Then set the high needle for best rpm. Find the rich rpm drop of the high needle. Stay just clear of that rpm drop.
Now a cold engine should not accept throttle until well warmed up. Once warm, throttle response should be crisp. If not, richen the L-needle slightly. This will improve the hot starting, and also add to the idle shake. This is normal, and just the thing that two stroke gas engines do.
P.S.
fine tuning the L-needle should not be done hamfisted. Turning the screw a hair makes a difference. Using 1/4 turns, or even 1/8th turns will probably overshoot the ideal setting. In some carbs with steep idle needle taper, 1/16th of a turn is too much.