remove carb top. take slide out.
remove throttle cable from slide.
remove spring, remove retainer plate (may or may not have one - depends on carb model)
push needle out of slide from the bottom.
there's a clip on the needle.
which position is it in? needle has either 3,4, or 5 grooves in it. moving the clip UP lowers the needle and leans it out. moving the clip DOWN raises the needle a richens it.
here's a pic of a needle in position 4 - the richest position on this particular needle.
you mention it has problems at 1/8-1/4 throttle ? that's either pilot jet or needle positon/taper USUALLY. it could be airscrew too....
you're in canada. it's probably cold there :) i'm betting richening up the pilot one step, and maybe raising the needle up a notch will compensate for the cold. but it may be too rich when the temperature increases. you say it runs great a wot? with how cold it is it may be slightly lean on the main too. don't forget 2 strokes run the best right before they blow up :)
you need to google '2 stroke jetting' and go through the whole process. keep in mind, that your proper jetting at current temperature will most likely be too rich when the ambient temperatures increase. keep in mind it's really hard to jet over the internet.