Sounds Like your low speed needle needs to be turned clockwise 1/8 of a turn at a time until the problem is eliminated. I find it best to start from flush everything if I run in to a tuning problem. After making all adjustment screws flush,SLOWLY turn the HSN NO MORE than 1/8 turn at a time clockwise.Continue until your performance at high end reaches its peak,Then Turn the HSN needle 1/8 of a turn back.You know when the engine has peaked because the top end will start sputtering.(If there is ever an absents of smoke at WOT,Stop Immediately! Turn whatever needle you were turning clockwise back 1/2 turn counterclockwise.Check for smoke at WOT.)
Now,Adjust Low Speed Needle.The manual recommends you do not touch it.Frankly,you can't get performance like originally intended without adjusting it.Your engine will surprise you when properly tuned.Begin turning LSN Clockwise 1/16 turn at a time until engine reaches its low end peak with perfect transition to full top end.(Again,No White Smoke = BAD! Stop what you are doing and turn LSN 1/8 of a turn Counterclockwise.)
After all of that,check engine temp and see if it matches with the manuals normal temp.It should,if not, back BOTH Needles off at 1/16th turn counterclockwise,monitor Temp. For a few minutes,then adjust more if necessary to match manual specs for temp.
Congrats! Your engine should be tuned.
If its still not perfect try the same process with the midrange needle.
