Took me a few months to figure out how to string my husband's trimmer... a Ryobi electric double threader, model 137r. Always worked fine for us but with hubby gone, (am recent widow), though it runs, it suddenly doesn't cut anything.
I noticed some times the head doesn't rotate fast or agressively like it used to so it wacks. Could I have put it together wrong after I took it apart to locate the broken line inside the reel. I did follow manual, cleaned it, and put it back together again, tightening bump knob. Then, I restrung it.
Now motor sounds like its working but I noticed cool air coming out of motor area at top, (maybe that's good?) BUT, worse is now it does not cut anything.