I've put new chains on and keep the oil filled, but after just a few cut the chain will become so loose that it falls off the chain bar. My model has the little asjuster wheel, so all I have to do is loosen bracket and turn wheel; it doesn't appear to just loosen a little but a-lot and falls off the bar!

Garden - Poulan - Pro 42CC 2 Cycle Chainsaw, 18"