I had the exact same mower, same model number, and.....same problem. Drove me nuts, tried checking everything, replaced the coil, check compression, etc. Pulling the plug help cool it back down quicker. Cold no problem, hot forget it. I resorted to using a Velcro strap on the handle to keep the mower running anytime I needed to stop. Not the safest, but at least I was mulching. After a few seasons and my son getting old enough to help, I sold it and got a Honda. I do miss that LB. Wish they still sold the two strokes.