Ok this trimmer is not my main trimmer its a backup I use all new trimmers but this is mainly if anything breaks. anywho I bought this one used for 75 bucks. Its a all black plastic M-line trimmer made by Maryuama im sure I spelled that wrong . I have taken off the screen on the muffler cleaned out the muffler put in a new plug and air filter. Checked for interference with the spark . The ignition works fine. the main problem is the thing will not rev out it sounds like its loaded up and the motor will not clean out which shouldnt be the case its running 50:1 gas/oil mix. If I have it full throttle and put it into a area of grass you can watch the string stop moving. Its lost all power. The string never gets longer than a few inches no where near out of hand. The end of the shaft is always kept greased. Geez I cant think of anymore things to defend myself against. could it be that it is flat worn out and that the rings are worn and not sealing that well ?