Thought I would give an update. The CS-400 is running nicely now, running and cutting like a champ. For awhile it had a heckuva vacuum leak somwhere, never could find the exact source. I removed the carb and intake, inspected everything, found no problems. Carefully reassembled and now it runs great. I'm guessing a gasket was not seated properly or something like that. Hopefully it will behave from now on.
This has whetted my appetite for more Echos. I found a CS-450 missing the bar, chain, and clutch cover on Fleabay for $65.00. I took a chance on it and found that, while it looks beat, apparently hasn't been used much, stil has lathe lines on the piston. Replaced the missi g parts and now it's doing great. I also dug out my basket case CS-3000 that I've had for awhile. Rebuil the carb, replaced a few broken pieces, and did a basic rebuild on the engine and now that one is doing great also.
