After years of listening to customer complaints about their inability to address the symptoms of poor Gold Wing performance and ruthless exploitation by many repair shops in the 1980s, we were forced to look into the problem. In 1990, a written solution was presented and delivered to my clients without any obligation on the part of the reader to buy anything. We received hundreds of thanks from customers and from those who never bought parts from us but took the time to write to us. Those who have replaced based on our solution and tuned their engines have eliminated a whole host of problems including burning head gaskets and over the years we have received many reports of great improvement in fuel economy. fuel and overall performance.

AIR CUT-OFF VALVE

The air shut-off valve is an extremely important part of the air/fuel intake system that is often overlooked by even competent mechanics, most of whom are not even aware of its existence or how it works. Over time, air cut valves will harden, puncture and/or disintegrate, leaving your motorcycle in a permanently poor low RPM range (0-2200).

Most early model Honda, Kawasaki, Suzuki and Yamaha motorcycles use air cut-off valves. Every Honda CB650, CB750, CB900 and GL1000 has one, located on the air intake tube between the air cleaner box and the manifold. The GL1100 has four, located in the upper air intake passage of each carb, and each GL1200 has one located in the timing case below the air cleaner box similar to the GL1000.

These valves are “air stoppers”, along with the carburetor O-rings, which serve to restrict airflow, increasing the air-fuel mixture ratio when the carburetor sliders are in the lower RPM range, up to close so the machine starts and idles smoothly with virtually no throttling and accelerates quickly with no stumbling or hesitation.

When typical starting requires a long, intense throttle to keep the bike going, when it stalls and hesitates even while “warming up” and when it backfires while turning off the throttle while riding, most people will start to messing with the air screws to try to overcome the problem, only making it worse along with lowering your gas mileage.

Operation with dysfunctional air shut-off valves can cause serious damage or failure of the engine. When the valves are dysfunctional, the engine draws almost all of the air in the low RPM range through the carburetors and into the combustion chamber. The air-fuel ratio is extremely poor with pre-ignition well before the normal ignition point of 38 to 40 degrees, creating a huge amount of heat, without energy, that is trapped for a longer period of time in the cylinder before for the exhaust valve to open. .

This heat rises primarily through the cylinder head, gradually incinerating the head gaskets and allowing engine coolant (antifreeze) to seep into the engine. You can easily tell when you’re having trouble by a puff of bluish-white or white smoke when you first start the engine. Don’t leave him alone. Change the head gaskets right away or you could pull out the bottom end bearings, ruining the engine.

For those of you installing new exhaust systems, they will discolor your head tubes either blue (lean condition) or gold (rich condition) if the signs are ignored. You can fade your pipes with Blueway or Blue-Off, but be careful not to rub off the chrome, just rub gently. These bleaching compounds are usually found at a Harley dealer or Harley-oriented aftermarket store.

Genuine Honda pipes, like many Yamaha pipes, have a double wall for a portion of the head tube which masks discoloration, but also masks poor tuning. Even if your pipes are original and still in good shape, don’t think you’re safe if your motorcycle has some or all of the functional and performance characteristics of a dysfunctional air cut-off valve.

If your 1975 to 1987 Gold Wing isn’t getting 50 to 58 miles per gallon (20 to 23 kilometers per liter), you have one of the most obvious signs of trouble. Your air screws have likely been removed to try to overcome the effects of malfunction, stumbling, starting, stopping, and neglect.

INSTALLATION GUIDELINES

Consult your Clymer, Haynes, or Honda shop manual for installation location and procedures.

Replace the air shut-off valve(s), then re-time all four carburetors to the #3 carb vacuum level using a mercury carb timing tool (carb bar) or carb timing tool. vacuum gauge The number 3 carb is the factory set constant flow carb.

DO NOT attempt to configure by ear or just by guessing, as the results can range from pathetic to disastrous.

DO NOT deviate from your Honda, Clymer or Haynes manual book setup. People wiser than all of us designed this very effective and efficient intake and carburetion system.

To further insure against any additional vacuum loss, replace the inexpensive carburetor manifold o-rings. Vacuum loss can occur there and mimic the effect of a bad air cut-off valve. Glue a new set with Vaseline and make sure they are sealed with an ether check.

© Saber Cycle®