I have a couple of Shindaiwa 260 trimmers with a few hundred hours on them. They are probably about 5 years old. They start easily with choke and throttle and have great high end power, but when you let the trigger go to idle down they want to die. If I keep the rpms a little higher than idle, it will not die. It is not a problem with the idle setting. I have had this problem previously with backpack blowers and as they get older the crankcase seals begin to leak and it sucks enough air at idle to kill it. I was wondering if this might be the same problem. The other possibility I thought of was a carb diaphragm. Any help with this would be appreciated. Is there a test I can run to diagnose whether it is the seal problem? Also, does anyone know if the crankcase has to be opened up to replace these seals. In the blowers, the seals are accessible without complete dissassembly. One seal is accessible after removing flywheel. I think the fan has to be removed to get to the other one.