How to check Intake Air Temperature System

Information and questions on GL1500 Goldwings (1988-2000)
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1995 GL1500A Aspencade

How to check Intake Air Temperature System

Post by vladimirch »

I wanted check Intake Air Temperature System on my GL1500 1995 European version. It sounds a bit horrible and you can see step by step procedure in service manuals. It’s exact scientist task and you have to remove the air cleaner housing from the carburetors and release or squeeze some tubes.
I made some changes to check IAT easier way. What do you need? Room – garage temperature below +11°C. You have to open air box like for air filter change. And you can use vacuum gauge (which is not necessary.
1st step is IAT Vacuum Actuator inspection. You can use vacuum pump with specified vacuum 200 mmHg or you can test by your mouth – you will see some duct valve motion. Vacuum should hold.

All other steps you can see in my attached short video. This video has three parts. In 1st part you can see real vacuum value which will be used for Duct Valve operation and you can see that IAT Thermal Vacuum Valve operates the right way. In 2nd part I used hot air gun again to test IAT function with IAT Vacuum Actuator connected to IAT System. In 3rd part you can see final check (or 1st check?) of Intake Air Temperature System as whole. Everything is completed and it’s real live check. You do not need vacuum pump and one small pocket mirror should be enough. I am delighted to say that my IAT Vacuum Actuator + Duct Valve + IAT Thermal Vacuum Valve + IAT Check Valve + Air Tubes 1, 2, 3 + Hot Air Pipe work properly. :D
Remember you need room – garage temperature below +11°C. You will see no Duct Valve motion with temperature above +18°C. I had +6°C in my garage and I was waiting more than 4 hours to repeat video 3rd part again for camera.

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Why do we have Intake Air Temperature System in our GL1500s? It’s carburetors icing protection when we ride our motorbikes in cold weather. Hot air is sucked from exhaust manifolds to air box by Hot Air Pipe.

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Re: How to check Intake Air Temperature System

Post by WingAdmin »

It's not just for cold weather - the air cools significantly as it accelerates across the venturi, and especially when fuel is introduced and evaporated. It can be a humid 75 degrees outside, and with the proper conditions, you can still experience carburetor ice. Small airplanes have carburetor heat controls that inject hot air into the intake, and standard procedures have you turn it on whenever you reduce power (i.e. reduce venturi size and restrict airflow), or at certain temperatures or humidity levels.
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