you could have a poor seal where the carb meets the reed block or where the reeds meet the case,,or your case gaskets are loosing their seal ,,check all that first,,,im assuming youre referring to the idle set screw,,,most people toss them out anyway.
I have had my DL50 for 2 years now and it has been virtually problem free. I have always stopped it by closing the throttle. However this does not work any longer. I think it is the caburator that is getting worn and has to be replaced or could it be anything else. The idle screw has been taken away so that is not he reason.
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