Before you go wasting money on parts, like I almost did, you should should try narrowing down the root cause. For example why would the needles suddenly need adjusting? Probably because something is wrong. Like for example with the carb or in my case, the fuel tank cap vent got plugged and was pressurizing the tank. This caused a few problems for me. I'd remove the carb and make sure the innards look good. No debris, no gumming, membranes are flexible with no tears or pin holes. I use no ethanol gas which avoids a lot of gumming up. Also look at the tank. Does it have a vented cap? Make sure air can pass through. How's the fuel filter? Those are pretty cheap to replace. Look at everything.
I did buy one of those tuning tools that sledman posted. These are a must have especially since Homelite factory sent mine so lean it wouldn't barely run. Once you tune a 2-cycle gas engine with these, it really should not need it again if you're only running it in summer like me. And I only usually have to adjust the low needle, the one closest to the engine. High needle is not as critical since I don't run at full throttle much. I used to fly 120cc opposed twin 2-cycle engines in big 110" wing span RC airplanes. Your engine has to be running 100% if you don't want to crash it in a dead stick.