Information and questions on GL1500 Goldwings (1988-2000)
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Joined: Mon Feb 10, 2014 12:48 pm
Location: timbuck too , England, United Kingdom
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Post by wingdings »


So, you went and brought a Honda Goldwing GL 1500 -?? Back in its day it was the most advanced and luxurious motorcycle available on the market it was also one of the most complex motorcycles too.

Mother Honda with its obsession with carburettors on their motorcycles decided to use air instead of fuel to inject the engine.

Hence that's why on early Goldwing's there were seven induction systems on early models and six induction systems on later models and all the vacuum lines and other modifications and upgrades on too, one of the main changes was the removal of the High-altitude compensation System.

Please watch the video below: -

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As you can see then before you start working on your wing it is most important to both understand how each of the systems work and when they come into play also! This will help you find and fix problems quicker too and save you a ton of cash in the process too.

At the centre of the system are the duel down draft computer assisted C.V carburetors.

So, let's start dealing with each system in turn then: -

System 1

The intake hot air system -

How it works

This system is designed to improve throttle response - power and driveability in cold weather, when the outside temperature is below 55degrees Faren Hight. pre heated air from the left side manifold is added to keep air intake warm
manifold vacuum is added via a one-way valve to a vacuum actuator which controls a flap door this is also teed to a bi-metalic valve did you notice that all the vacuum tubes on this system are colour banded pink and numbered corresponding to numbers on the service vacuum diagrams for your model. Take note of this as it is possible for you to have the same number on the system. However, it will have a different colour banding this is why it is especially important to take note of the colour banding and the corresponding numbers to that part of the system.

How to test and check the system

In the interests of keeping this how to short please watch the video below

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System 2 The heated intake manifolds and carbs: -

The second temperature control is the heated intake manifolds and carbs, to keep fuel atomised at low temperatures and prevent carburettor icing the intake carburetors and manifolds are heated by coolant this controlled by a thermo valve it's not easy to gain access to and is located below the righthand manifold.

Here how it works -

When the engine is cold the thermo valve is open, warm coolant flows from the hot cylinder heads though the carburetor manifolds and carburetor base before returning to the radiator. Then when the coolant reaches 170degrees the thermo valve closes letting the coolant bypass the manifolds and returning directly to the radiator this prevents the carbs and manifolds from getting too hot.

The thermo valve is the heart of this system and as stated before it's not easy to get too however generally speaking is more trouble free than any thermostat.

Trouble shooting - testing -servicing

Problems on this system range from rotten coolant pipes to a stuck thermo valve and if it's the thermo valve that's the problem here are the signs either the carb manifolds and intake manifolds are too hot or if the valve is stuck closed the opposite would apply, they would remain cold as coolant would be unable to flow through them.

If you have established the thermo valve is faulty then you are in for a roller coaster of a ride to get to it I myself have just done this job and it's not for the faint hearted either. The coolant has to be drained the carbs have to come out to access the right-hand manifold and then you have to remove the coolant pipes to the right intake manifold before you can unbolt the manifold to gain access to the thermo valve below. On my wing these coolant pipes were starting to split on the ends and the rubber was perished and hard too after 32yrs on the bike and the thermo valve looked bad too.

The biggest problem you will face is finding a replacement mother Honda stopped making these little puppies a long time ago and to add to this problem also is the fact that there is only one on each wing too so unless the engine is sold for parts you will not be able to buy a second hand one as these are sold with the used engine as a rule.

Having said that I did manage to free mine up again by boiling the valve in Prestine coolant flush in a pan on the stove then gently taping it with a rubber mallet to free the lime scale up inside what you don't want to do is try blowing it out with an airline that will break it altogether, by boiling it up on the stove it simulated it being on the bike and I was able to by tapping it break up the lime scale inside the valve then using the manual I tested it and it was fine.

I cannot stress enough here if you make up your own coolant and live in a hard water area then don't use tap water ever!!better still use Honda coolant premixed instead.

Here are some pictures I took of the thermo valve after 32 yrs. on the bike and operation too.


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