GL1000 carburation problems


Information and questions on GL1000 Goldwings (1975-1979)
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kapiteindejager
Posts: 4
Joined: Sun Jun 13, 2010 2:28 pm
Location: Groningen, the Netherlands
Motorcycle: GL 1000, K2

GL1000 carburation problems

Postby kapiteindejager » Fri Jun 18, 2010 6:12 am



Dear all,

I just serviced my GL1000, year of manufacture 1977. It had not been used for some 20 years and the only major problem was an excessive dirty fuel system which has been resolved. The bike is running now but is sputters when the throttle valve is only slightly opened, as soon as you give a little bit more throttle the engines runs perfectly. After riding it for a while at low speed with minimal throttle opening all spark plugs indicate a lean mixture so it seems likely that a lean mixture might be the cause. As far as I know there is no means to adjust this, the fuel jet and air jet sizes are correct. I was just wondering if the air cut-off valve might play a role. My common sense says not: in my view the valve is constantly open and should only close for a short on deceleration when the throttle valve is suddenly fully closed and since there is no backfiring the air cut-off valve should function properly. However, several sources on the internet suggest that the functioning of the air cut-off valve would be more subtle than I assume, e.g. Randall: . ‘Often, they fail in a more insidious way by shifting the "function point" of the valve to a higher vacuum / rpm level than designed. So, even though the diaphragm is intact and will hold a test vacuum…you can get an excessively lean condition resulting in poor off-idle throttle response. Typically, this may also lead to a condition where the bike requires lots of choke until it is completely warm before it responds well to the throttle.’
I do not understand in which way an even disfunctioning cut-off valve could disturb a correct fuel-air mixture in my case. Anyone any reasoned idea or practical experience demonstrating that this might be the case or not?
Btw: ignition, compression, synchronisation ect. have been properly checked and are OK

Jeroen.



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WingAdmin
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Re: GL1000 carburation problems

Postby WingAdmin » Fri Jun 18, 2010 12:21 pm

While I don't pretend to understand it either, I have heard the exact same thing: air cut-off valve for off-idle problems. And if Randakk's says it about GL1000 carbs, I would take it as gospel truth.

Chuckv1947
Posts: 1
Joined: Fri Jun 25, 2010 9:03 pm
Location: Houston, texas
Motorcycle: 1979 GL1000 Honda Goldwing

Re: GL1000 carburation problems

Postby Chuckv1947 » Fri Jun 25, 2010 9:14 pm

Normally the symptom of the fuel air cutoff valve is back firing when the engine is coming down off of high rpms. There is an issue with off idle on the years of wings like yours which requires replacing a air jet that is on the elbow fitting on the side of the carb. Their is a website hosted by a gentleman who is really knowledgeable about our bikes and the site has the off idle fix written up. The website is http://www.randakks.com/. Look under the tech tip section and you will find the write up on how to implement the fix.

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kapiteindejager
Posts: 4
Joined: Sun Jun 13, 2010 2:28 pm
Location: Groningen, the Netherlands
Motorcycle: GL 1000, K2

Re: GL1000 carburation problems

Postby kapiteindejager » Mon Jul 12, 2010 3:08 pm

Dear all,

The problem has been solved: I have re-adjusted the idle air screws. Using the standard manuals you can easily make a mistake which the former owner apparently did: do not look at the year of manufacture of your motorcycle but look at the carb identification number, there are differences between european and overseas models: in 1977 there were two types. My carb (No: 755) needs 1 3/8 turns while the 764 overseas type needs 2 1/2 turns. It improved but was still not solved: afterwards I cleaned the air cut-off valve ultrasonically, replaced the membrane-valve unit (which looked fine !) and O-rings and now it runs like it should: slightly more than 1000 rpm in second gear with a very smooth running engine ! Ready to conquer the world with my bike !

Thanks for your input.




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