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C'roam
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Can the air cut off valves be installed without removing the carbs from the bike?

Phil
 

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I think so. Remove the air filter housing assembly, Then you can see them to get them out. That is on the GL1000 I might be wrong for the 1100. Is that what you are asking about?
 

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Very hard to do it with them off the bike and not split..on the bike I doubt it. You need a right angle Philips screw driver and you'll only be able to turn it a 1/4 turn at a time..in a very tight space. Then if you get the covers off and the parts out getting them back in with the spring lined up and the diaphragm in place will be very hard.
 

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as for the 1100, they are on the side of the carbs, so you can change two, but the other two end up between carbs and you have to separate them. correct me if im wrong but i changed a set on a 81 1100 and had to take them apart
 

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C'roam
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Thanks for the quick replys, living in an apt complex without a garage means that I cant spread bike parts all over the carport area. So..I was curious to see if the job could be completed without removing the carbs. Something I could do in a stealthy way on a weekday morning when nobody is around.
I will have to take a look see and judge from there.
Thanks again for all the great info.
Phil
 

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i have a 79 and a 83 i think there is one on 79 and can get to it with airbox removal, the 83 has one for each carb, remove carb assembly. or at least remove intake bolts and slide assembly around to gain access
 

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Phil C wrote:
Thanks for the quick replys, living in an apt complex without a garage means that I cant spread bike parts all over the carport area. So..I was curious to see if the job could be completed without removing the carbs. Something I could do in a stealthy way on a weekday morning when nobody is around.
I will have to take a look see and judge from there.
Thanks again for all the great info.
Phil
I've not done this with a rack on a bike, but off and not seperated.

I use channel-locks on the in-board phillips-head screws of the valves covers to remove them. I replace all screws with allen-head screws.

Trying to do that on the bike, and giving myself enough room, light and comfortto get it done right would be a challenge, but might be doable. If you can do it (and it's right when you're done) ...you'll get my applause. No doubt about it.
 

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Agree with William, if you are going to change the cutoffs you might as well go all the way and be done with it. If the cutoffs are bad chances are you have more problems as well. Just went out and looked my 83 over and can promise you way more time to do it on the bike than take them off. Having rebuilt mine I am sure getting the spring and diaphram lined up on the ones between carbs is nearly impossible. take the carbs out and take them inside, a pretty quick job. Then you can take your time. Definitely cover the intakes on the engine while you have them off though. I have used duct tape , works well
 

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I've changed several during carb clean ups on 1100s in my previous shop and wouldn't bother to try with the carbs on the bike. You don't have to remove a whole bunch of stuff to get the carbs off the bike and you can do the job by removing the rear two carbs which makes the front two easier to get at.
 

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C'roam
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OK, you have convinced me, I will remove the carbs in order to tackle this job. Another question I have is about the "Plenum" when seperating the carbs.
What is meant by "Pleneum"? Im sure its some kind of seal but the use of a word such as this makes me think it is a very special seal and i dont want to damage it if its so special you cant replace it.
 

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It's an "air chamber" according to Honda. I agree. There is no "plenum" area on a factory set of carbs. A plenum is after a carburetor andnot before it in the real world of engines. Erroneous fear comes from calling it something that it is not.

There is a seal. O-ring material. I've always been able to re-used them. Do a inspection after a cleaning to know whatyou need and don't need.
 

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C'roam
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Now Im wondering if it was Hondas less than stellar translators or a British term/word.
Anyway thanks, I will reuse any o rings that I can.
Wondering if Armorall or something similar is good to use on o rings in order to extend their life.
 

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I would buy new for ALL rubber parts if I were you , unless they were replaced not too long ago. You can get them here.

http://randakks.com/Carb Parts.htm
 

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Some good advice above. Someone contacted me privately and asked for my response on this thread.

As noted, replacing the air cut-off valves on a GL1100 is possible without “splitting” the carbs, but it’s a bit of a “science project” and usually not worth the heroic effort. It’s a much easier task to remove the carbs from the bike, split the carb pairs from the central plenum and then separate the pairs from each other. Usually, there are other good reasons to do that anyway if you are “in this deep.”

Here’s a photo of the GL1100 plenum referred to:



Respectfully, I think it is perfectly acceptable and appropriate to refer to this as a plenum. For decades, that’s what Honda ‘Wing mechanics have called this.

True - the official Honda nomenclature calls this assembly:

“CHAMBER A, AIR” and “ CHAMBER B, AIR”

But, that’s the clunky Japanese-to-English translation which incidentally has given us pearls such as:

“BAR, PILLION STEP”...for rear foot pegs!

The definitions for plenum (derived from the Latin plunus) includes any reservoir that holds matter...particularly air. So, plenum is a perfect description of this component’s use and function.

Eventually, strict engineering usages of the word plenum evolved (in some contexts) to include the concept of a “pressurized” chamber which is not an issue here. But, it can apply.

Roman engineers rarely dealt with pressurized vessels beyond the trivial levels of pressure in water transit oriented civil engineering projects.

But, in modern industrial times - plenums routinely carry solids, liquids as well as gases in a wide range of complex industrial applications including factories, power plants, ships and submarines.

For an example closer to our world, here’s an actual pressured early ‘Wing plenum I designed for use with a supercharger:



Continuing in our world, the location of any intake chambers relative to the carburetor(s) is an important engineering consideration. But, neither location (before or after the carb) precludes the use of the description “plenum.” Companies such as K&N and others routinely refer to chambers positioned before and after the carb as a plenum. Rightfully so I would say. Generally, in the automotive world - plenums after the carb are usually called intake manifolds. Sometimes, the automotive usage of plenum limits the reference to just the “open” collector portion of an intake manifold. But, there are many exceptions to way plenum can be used in the automotive context.

In any case, I believe the use of plenum in the context of this particular thread is an accurate and apt term. Efficient as well - given that it’s a mere 6 letters with no ambiguity!

No matter what I think, the term plenum to describe this piece is well-entrenched and here to stay.

Finally, the GL1100 central plenum gasket looks like this:




High quality plenum gaskets made of Viton (like ours) last indefinitely when properly installed. However, once they are placed into service, it is considered a best practice by most experienced mechanics to replace them whenever they are disturbed for any reason.

The OEM Honda plenum gasket is also high quality (but not Viton). Recently, lower quality aftermarket plenum gaskets have found their way to the marketplace. I recommend avoiding those.

There are companion components that are generally replaced along with the plenum gasket as well. These include:

* carb-to-plenum FUEL seals (2 large and 2 small on a GL1100)
* carb-to-plenum AIR orings

Here are some more GL1100-specific carb details:

http://www.randakks.com/TechTip46.htm

Good luck on your project.
 

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Wow! :claps: Now there is a thorough and complete answer for you.
 

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One thing to consider when trying to reuse a plenum gasket is that there are 2 fuel passages under pressure that run through it. One for accelerator pump and one fuel supply. Not a good place for a leak! I have tried several different gaskets and Randakks is the best I have found.
 

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I think it fair to call that air chamber to which the carbs are attached a plenum. Under one definition plenum means any air filled chamber. For those who enjoy nit picking you could argue that it doesn't satisfy the definition in physics as there it means a chamber containing a gas at higher pressure than that on the outside. It would be foolish to nit pick to that point because if you want to stick with that you'd need to call tires plenums. My suggestion is to call it whatever the heck you want but if someone does call it a plenum there's no need to correct them because they are just as correct as the dissenters.
 

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lol! I never worry about what anyone calls anything as long as I can figure out what they are talking about. That being said plenum applies to many things, in furnaces they have hot air plenums but also sometimes cold air return plenums too. Plenum to me is the area where anything collects for distribution, under the carb in a manifold for fuel and air mix to to go out the runners to cylinders and in this case th ecollection point for air to go to carbs and runners
 

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TBear wrote:
lol! I never worry about what anyone calls anything as long as I can figure out what they are talking about. That being said plenum applies to many things, in furnaces they have hot air plenums but also sometimes cold air return plenums too. Plenum to me is the area where anything collects for distribution, under the carb in a manifold for fuel and air mix to to go out the runners to cylinders and in this case th ecollection point for air to go to carbs and runners
Psst... the air in a cold return plenum would be at lower pressure than the outside air. Same as the air in a 'Wing plenum.
 
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