AIR CUTOFF VALVES

THE AIR CUT-OFF VALVE IS AN EXTREMELY IMPORTANT PART OF THE FUEL/AIR INTAKE SYSTEM THAT IS FREQUENTLY MISSED EVEN BY COMPETENT MECHANICS, MOST OF WHOM ARE NOT EVEN AWARE OF ITS EXISTENCE OR HOW IT FUNCTIONS.

EVERY GL1000 HAS ONE LOCATED IN THE AIR INTAKE TUBE BETWEEN THE AIR CLEANER BOX AND THE MANIFOLD. EVERY GL1100 HAS FOUR LOCATED IN THE TOP AIR INTAKE PASSAGE OF EACH CARBURETOR. AND, EVERY GL1200 HAS ONE LOCATED IN THE PLENUM BOX BELOW THE AIR CLEANER BOX, SIMILAR TO THE GL1000.

THESE VALVES ARE "AIR BLOCKERS", ALONG WITH THE CARBURETOR MANIFOLD O-RINGS, SERVING TO RESTRICT AIR FLOW AND INCREASE THE FUEL/AIR MIXTURE RATIO WHEN THE CARB SLIDES ARE IN THE LOWER RPM RANGE DOWN TO CLOSED. WITH HEALTHY VALVES, THE MACHINE WILL START AND IDLE SMOOTHLY WITH VIRTUALLY NO CHOKING AND ACCELERATE RAPIDLY WITH NO STUMBLE OR HESITATION.

MOST PEOPLE WILL START FOOLING WITH THE AIR SCREWS TO TRY TO OVERCOME STARTING THAT REQUIRES HEAVY AND PROLONGED CHOKING TO KEEP THE BIKE RUNNING, STALLING AND HESITATION EVEN WHEN "WARMED UP", AND BACKFIRING WHEN THE THROTTLE IS SHUT OFF WHILE CRUISING. THESE ADJUSTMENTS ONLY MAKE IT WORSE, ALONG WITH KILLING THE GAS MILEAGE.

WORSE YET, EXTENDED RUNNING WITH DYSFUNCTIONAL AIR CUTOFF VALVES CAN CAUSE SEVERE ENGINE DAMAGE OR FAILURE. WHEN THE VALVES ARE DYSFUNCTIONAL, THE ENGINE PULLS IN JUST ABOUT TOTAL AIR IN THE LOW RPM RANGE THROUGH THE CARBS AND ON TO THE COMBUSTION CHAMBER. THE FUEL/AIR RATIO IS EXTREMELY POOR WITH PRE-IGNITION LONG BEFORE THE NORMAL 38-40 DEGREE FIRING POINT. AN ENORMOUS AMOUNT OF HEAT IS GENERATED WITH NO POWER, WHICH IS TRAPPED A LONGER PERIOD OF TIME IN THE CYLINDER BEFORE THE EXHAUST VALVE OPENS. THIS HEAT GOES MOSTLY UP THROUGH THE CYLINDER HEAD GRADUALLY INCINERATING THE HEAD GASKETS AND ALLOWING ENGINE COOLANT (ANTI-FREEZE) TO SEEP INTO THE ENGINE.

YOU CAN EASILY SPOT WHEN YOU ARE IN TROUBLE BY A PUFF OF BLUISH-WHITE OR WHITE SMOKE ON FIRST STARTING THE ENGINE. DON'T LEAVE IT ALONE. CHANGE THE HEAD GASKETS IMMEDIATELY OR YOU COULD TAKE OUT YOUR BOTTOM END BEARINGS AND RUIN THE ENGINE.

ALSO, FOR THOSE OF YOU INSTALLING NEW EXHAUST SYSTEMS, FAULTY VALVES WILL DISCOLOR YOUR HEADPIPES, EITHER BLUE (LEAN STATE), OR GOLD (RICH STATE) . YOU CAN DE-STAIN YOUR PIPES USING "BLUEAWAY" OR "BLUE-OFF" BUT BE CAREFUL NOT TO RUB THE CHROME. JUST DAB GENTLY. THESE COMPOUNDS ARE USUALLY PURCHASED AT A HARLEY DEALER OR HARLEY ORIENTED AFTERMARKET SHOP.

HONDA GENUINE PIPES, LIKE MANY YAMAHA PIPES, HAVE A DOUBLE WALL FOR A PORTION OF THE HEADPIPE WHICH MASKS THIS DISCOLORATION BUT ALSO MASKS A BAD STATE OF TUNE. SO, IF YOUR PIPES ARE ORIGINAL AND STILL IN GOOD SHAPE, DON'T THINK THAT YOU ARE OK. IF THE BIKE HAS ANY OR ALL OF THE DYSFUNCTIONAL AIR CUT-OFF VALVE RUNNING AND PERFORMANCE CHARACTERISTICS, YOU'RE IN TROUBLE.

IF YOUR `75 - `87 GOLDWING IS NOT GETTING 50 TO 58 MILES PER GALLON (20 - 23 KM/ LITER), YOU HAVE ONE OF THE MOST OBVIOUS SIGNS OF TROUBLE. IT IS LIKELY YOUR AIR SCREWS HAVE BEEN BACKED OUT TO TRY OVERCOME THE EFFECTS OF THE POOR RUNNING, STUMBLING AND STARTING WITH STALLING AND QUITTING.

RESYNCHRONIZE ALL FOUR CARBS TO THE NUMBER 3 CARB VACUUM LEVEL USING MERCURY CARB STICKS OR VACUUM DIAL GAUGES. STAY WITH STRICT USE OF THE SETTING LEVELS IN EITHER THE HONDA, CLYMER OR HAYNES MANUALS. DO NOT ATTEMPT TO TUNE ANY OTHER WAY. GUESSING WILL NOT WORK AND CAN CAUSE DAMAGE!!!