GL1200A Carb Question


Information and questions on GL1200 Goldwings (1984-1987)
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mjk
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GL1200A Carb Question

Postby mjk » Sun Jun 29, 2014 11:40 am



Hi! I am a new member and I urgently need help!
On the edge of the carb where the diaphragm seals should there be a through hole in the casting? The diaphragm has an opening in the sealing edge that lines up with an indention in the carb casting and cover. The indention in the carb casting looks as if it never had a through hole but other people have worked on the carbs so I'm not so sure they didn't damage the casting.
Please help!



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WingAdmin
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Re: GL1200A Carb Question

Postby WingAdmin » Mon Jun 30, 2014 10:25 am

mjk wrote:Hi! I am a new member and I urgently need help!
On the edge of the carb where the diaphragm seals should there be a through hole in the casting? The diaphragm has an opening in the sealing edge that lines up with an indention in the carb casting and cover. The indention in the carb casting looks as if it never had a through hole but other people have worked on the carbs so I'm not so sure they didn't damage the casting.
Please help!


Any chance you could include a picture to describe exactly what you're talking about?

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Ed Z
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1987 gl1200 Aspen
1983 gl650 Intersta

Re: GL1200A Carb Question

Postby Ed Z » Tue Jul 01, 2014 10:04 am

You don't by chance have the chrome after market tops on your carbs do ya ??? If so, many of them were not made correctly or don't fit correctly... If my memory serves there is (or should be) a notch in the top cover that alligns with the vent in the diaphram... If you should come to need a rebuild kit for the carbs, I can highly recomend Randal Washingtons kits... I have used his GL1200 and his GL650 kits with great success...

http://randakks.com/collections/kits

mjk
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Location: Magnolia, MS
Motorcycle: 1985 GL1200A Aspencade

Re: GL1200A Carb Question

Postby mjk » Wed Jul 02, 2014 12:45 pm

Image

Just below the screw hole on the right is a dimple in the carb. It lines up with the hole that is an intentional part of the diaphragm. It also lines up with a grove in the cover. The dimple seems to be a dead end with no through passage drilled or cast in it at the factory. Is that normal to not have a hole?

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Ed Z
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1987 gl1200 Aspen
1983 gl650 Intersta

Re: GL1200A Carb Question

Postby Ed Z » Wed Jul 02, 2014 2:08 pm

There has to be a way to vent the top side of the diaphragm... Else wise there would be a vacuum created preventing the slider from moving freely... Check for a notch in the carb top cover... This should line up with the area you mention on the carb body... Also check to se if there is a hole somewhere in the carb top cover to the outside... If not then the area you mention needs to be opened to outside air pressure... Anyway you go about it, the top of the diaphragm must not create a vacuum or pressure when the slider moves up and down...

Did you check the other carbs to see if this area you mentioned is drilled through ??? If so, then this one too should be... If not, then the top cover must have a hole to allow pressure equalization to the top of the diaphragm...

mjk
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Joined: Sun Jun 29, 2014 10:53 am
Location: Magnolia, MS
Motorcycle: 1985 GL1200A Aspencade

Re: GL1200A Carb Question

Postby mjk » Wed Jul 02, 2014 2:37 pm

Ed Z wrote:There has to be a way to vent the top side of the diaphragm... Else wise there would be a vacuum created preventing the slider from moving freely... Check for a notch in the carb top cover... This should line up with the area you mention on the carb body... Also check to se if there is a hole somewhere in the carb top cover to the outside... If not then the area you mention needs to be opened to outside air pressure... Anyway you go about it, the top of the diaphragm must not create a vacuum or pressure when the slider moves up and down...

Did you check the other carbs to see if this area you mentioned is drilled through ??? If so, then this one too should be... If not, then the top cover must have a hole to allow pressure equalization to the top of the diaphragm...

Yes, all four carbs are the same. No through hole in the area you would expect one. The cover has a notch but it just seems to give clearance above the area. I was hoping someone had some experience with this.
I don't quite understand the logic of the top of the diaphragm venting the vacuum as you suggest. I thought the hole in the bottom of the slide would create a vacuum above the diaphragm causing it to slide up in its proper operation.

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virgilmobile
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Re: GL1200A Carb Question

Postby virgilmobile » Wed Jul 02, 2014 3:31 pm

The top of the chamber at the diaphragm must be sealed from atmospheric pressure.
The only air flow should be from the hole in the bottom of the slide itself...

Below the diaphragm (underside) must to be vented...in the carb body...in the cavity well,there are vent passages...they must be clear... but above the diaphragm is sealed..

The "ear" is for proper alignment...It positions the slide "hole" toward the front(engine side) of the carb.

I'm going from memory...Ya'll know how that is. :lol:

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Ed Z
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1987 gl1200 Aspen
1983 gl650 Intersta

Re: GL1200A Carb Question

Postby Ed Z » Wed Jul 02, 2014 7:14 pm

I believe you just might be right with the seal requirement... The spring is on top of the slider and it would require vacuum to overcome the spring pressure trying to keep the slider closed...




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