Hi, i have recently brought an Echo 702vl. After reading many good reviews on the net thought id take a chance on owning one. It has a 24" bar and looks in good condition. Im not sure year of make,though it does have a serial number on. The problem is the chainsaw can be used for several minutes then the chain appears to go tight,as you hit the throttle can hear the engine trying to rev but the chain will not move. At this point the manual chain luber seems to be empty. If i slacken off the chain and re-lube it,she will run ok for a short period of time. There are signs of a small amount of oil in the oil tank,even if i fill to the top the level drops rapidly. Could it be a cracked oil tank fo perhaps the oil feed adjuster is knackerd so its dumping the oil too quickly? Is this a common problem? Any help would be much appreciated. Many thanks