I reach the stage in my rebuild where I started the engine today. All went well with only one small oil leak at the filter canister, the gasket for the lid was bad. My problem is that I can't get the engine to idle without the choke closed. The idle mixture screw doesn't seem to make much difference wherever it is adjusted. The engine runs smooth at 1000 rpm and up, anything lower it sputters and stalls. I rebuilt the WO carb., with a master kit, Any ideas?