Well I did get to running again. But I cant pinpoint what worked. I just kind of did everything. Cleaned the fuel tank out,new fuel line +filter,new impulse,new plug, dismantled the dukes carburetor completely set in it and all metal parts in acetone for 24hours followed with ultrasonic cleaner with just water and then iso to displace any water. then I found a bottle of carburetor cleaner in my medicine cabinet.....??(So that's why my spray on deodorant stung like hell!) I also used a small spray of starting fluid. Just enough to spray off the spark plug. I don't know if starting fluid is okay for chainsaws but I didn't think spraying the plug would harm anything.
We have sold a ton of 590's over the years, and have almost never had any carb issues with them, but strangely enough I just ran into one with the main nozzle check valve swollen up like crazy. I didn't know Walbro rubber did that. It's something I see almost exclusively on aftermarket carbs.
Could it be a counterfeit of a Walbro?
I think it's stupid they use rubber there when other carbs appear to use fiberglass resin or something like that. I've had it happen to mine, a friend had it happen to his, and another I know has replaced carbs several times. I almost blew the valve out once using carb cleaner.
damn they have gotten cheap on us. they used to us a material called mylar atleast i think that was the name of it. has a somewhat checker board pattern on it
The carbs on the old Stihl 021-025's have that style. I guess it's a stiff version of their tan pump diaphragms.
