I posted a question a few days ago about a LB DuraForce carb screen problem. After that was resolved, it has worked great -- until mid-morning today! It fired this morning, like usual, sounding and working fine. We used it for a couple of lawns, and was using it on the next one. It started to loose power, and within a few minutes, stopped running. I discovered it has no compression. I took out the plug, and see nothing unusual (I concede not much can be seen). The piston does move as expected when cranking. Also, when cranking, I hear a sucking sound, presumably from the carb area. The fact that it spins quite freely tells me there is a major problem, internally. The blade isn't loose, either the nut holding the blade to the adapter plate, or the lower engine bearing. When cranking, I hear a sound that is not usual -- I'm hard pressed to say it is a knocking sound, but can't describe it another way. It isn't as "solid" as I believe a knocking sound might be, but I believe something is loose someplace. I have not yet had a chance to take anything apart. I returned to pick up a backup machine, and finished out the day's mowing schedule. My only thought is that a ring is broken. If somebody is quite sure the problem is a major internal one, I wil get a short-block on order ASAP. If not, I'll take time to disassemble, and go from there. I would like to get it back in service quickly -- my backup is another LB, pre-DuraForce, but has seen many, many hours of service. Thanks.