You might consider this item: Randakk’s GL1000 Carb Rebuild Video
The air cutoff valve is a simple but vital component of the carburetor system on GL1000s. Its function is to eliminate backfiring on hard deceleration (throttle fully closed). Hard deceleration creates a high vacuum signal in the intake tract which activates the valve. When activated, it restricts the flow of air to the external idle circuit air jets thereby richening the mixture. This slightly richer mixture is calibrated to eliminate backfiring in this operational mode.
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