here is the deal, I have been running all redmax equipment all along, I have had no problems with any of it, until now. Both of my trimmers (BCZ2500S) are now having problems cranking, they act as if they are flooded all the time (pull and pull and pull). here is what I have done to try to remedy the problem: 1. changed filter elements 2. changed plugs 3. rebuilt carb with rebuild kit (on one of them) 4. removed carbon from exhaust ports 5. soaked mufflers in gas to try to break up any carbon 6. checked throttle lines and re-adjusted 7. removed carbs and cleaned with gas (removed gunk build up). 8. sprayed them with carb cleaner So far every remedy above helps for awhile, then same problem, my next move is to change the fuel filters. I should mention that I started having these problems after switching to Opti 2 oil from no smoke, I am now going to switch back to no smoke or redmax oil. Can anybody see anything I have missed or know of something else I can do? This is starting to really irritate me, nothing worse than pulling on equipment.