stihl 041

Any thoughts on the idle? And is the upper or lower screw the idle screw???

Under the carb is a non-metallic intake manifold. It is held the the cylinder with two bolts that take an allen wrench hex drive. It either comes loose or gets warped and the gasket gets sucked in between it and the cylinder-jug. Then, it sucks too much air and will not idle properly. Pull the top air-cleaner plate off the carb via two nuts and on screw. Then, pull the carb off. Check the two rubber hoses to the carb while you are at it (fuel pump and fuel hoses). Now, take out those two allen-drive bolts and remove that intake manifold. Once off, turn it upside down - you'll see that it's made out of some sort of fiber-composite material - but - it has two metal dowels going through it that the two bolts go through. Those dowels offen protrude to far and will not allow a new gasket to stay in place. So, lay the manifold on a piece of flat glass with a sheet of sandpaper on it - and rub the manifold gasket-surface over it until it's gets flat. It might take a while depending on how far the steel dowels are sticking out. If real bad, use a file on the steel. Once smooth - make or buy a new gasket (easy to make) and use some Loctite on both sides of the gasket and the two allen-drive bolts and reinstall the intake manifold. Rely on the Loctite to keep the bolts from shaking out - instead of overtightening them. Then, put the rest together. I did hundreds of them - as I said - it was such a problem with the 041s - we did it when they were new - to avoid having them come back.