The H screw adjusts the mixture from 1/3rd throttle to full throttle. The L screw adjusts the mixture at low rpm. The larger screw to the RH side of these adjusts the rpm for idle.
If you have opened (turned anti clockwise as if unscrewing) the H screw you will have leaned out the mixture too much and you will lean seize the engine if you are not careful. I would suggest going back to stock settings and starting again before something blows particularly in the cold weather (needs to run richer than in summertime!).
Screw the H & L screws in (clockwise) until they stop. Do not force them. Then unscrew the L screw 1 & 1/4 turns and the H screw 1 & 3/8 turns. This is factory settings. It should start and run ok ish at this and you will be able to adjust the idle screw to get that somewhere near.
Follow the tuning guide for adjustments but just take your time and make 1/16th adjustments at a time otherwise you may miss the sweet spot!
https://www.largescaleforums.com/showthread.php?t=2761
