I've owned quite a few of the low cost engines both in cars and airplanes. One thing I have found is that having a consistant feul pressure will help with tuning.Check your muffler any leaks at all causes eratic behavior. These engines are prone to having the mufflers rattle apart.A little bit of high temp silicone at all joints and a tight thru bolt will help, leave the baffles in. Not only do they help keep every thing tight they help to increace pressure to the feul tank.When you feed your carb with consistant pressure you will find that the needle valves will become much more sensitive and a good tune is easier to mantain.All things being equal you'll find that your not touching the needles nearly as much,maybee a click or two as weather changes. The very best way is to get a pump but I realize the extra cost makes the budget engine not so "budget" anymore.