Airbox halves

[Redman]

A few weeks ago Mr bwringer suggested that I should verify that my air box halves are well sealed.

No comprehenda.

I don't understand.

Tell me more, oh wize ones.



I know the two ends are well sealed (added weatherstripping last year), and the air filter is a new stock air filter with good seal.


I do see that there is a top and bottom half to the air box, and there doesnt seem to be any sort of seal between, that can see, and can see a space inbetween the upper and lower half. Oh, and, yes, I have the snorkle in place. I understand the snorkle have some effect on the high RPM functioning of the engine. My problem at present is more related to idle speed.

At present, I am replaceing the air box boots. A couple weeks ago I replaced the inlet boots (& o-rings and clamps) with some improvments. Symptoms are idle going high (2000 rom) after it warms up, but now that I have replaced the inlet boots, it only does it sometimes and not others. When it does it will keep doing it for the remainder of the ride. Next ride it may not do it. THis just started happening all at once this summer. This is what we were discussing when Brian suggested about the airbox halfs.

http://www.thegsresources.com/_forum/showthread.php?t=163879

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[Redman]

Now that I have taken the top(plastic) and bottom(metal) half apart, I do see a seal inbetween. It is not like a gasket inbetween the two halfs like I was looking for.
Is an oval rubber seal the shape of the air filter.




Cant really tell if it is making a good seal. But seems soft and plyable.

Maybe I will take another look at the oil and dust around that seal area.


Any words of wisdom...?

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[Nessism]

Looks to me that you've got it covered Dave. I'd put it back together and call it done.

[Redman]

Now that I have taken the top(plastic) and bottom(metal) half apart, I do see a seal inbetween. It is not like a gasket inbetween the two halfs like I was looking for.
Is an oval rubber seal the shape of the air filter.
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Maybe I will take another look at the oil and dust around that seal area.
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The seal itself seems okay.

But have some further observations that cause me to suspect it is not sealing well between the two halves:

- can see a pattern in the oil were it looks like about 1/3rd or more of the length on one end where the seal on the upper half may not be contacting the lower half surface. Seems to have dust and dried oil in that area where suspect not touching. The other 2/3rd can see an imprint of the seal in the clean (well, not dusty) oil.
ANd the plastic surface isnt flat, has a warp-whoow to it.

- WHen hold the two halves together and look into the box through the openings (where boots removed) can see that flanges on one end extend further into the upper half on one end than does on the other end.

- When holding the two halves together can slide the upper half sideways a good 1/4 inch one way and then the other way and see that the flange not contacting the seal on the sides (but maybe that is okay because the seal is suppoose to seal on the horizontal surface of the lower half.

Also observed that WHen I get out of bed in the morning before the alarmclock goes off, and go out in garage to look at this, wife gets annoyed when my alarm clock does go off, and then gets more annoyed when she cant find me. So my inpsection got interurpted.

Need to look some more.

Anybody noticed similar to this before? (with the air box seal, not the annoyed wife)

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[bwringer]

I discarded the now-useless rubber seal and used self-stick foam weatherstripping to seal between the halves, just the same as on the side covers. 'Twasn't rocket surgery.

Sealing the airbox halves will do you some good, but your idle problem is probably unrelated to this. You have an air leak and/or a clogged passage somewhere in the carbs or possibly a remaining leak in or around the intake boots (I know these are all-new parts).

I'd perhaps suspect the o-rings around the idle mixture needles, or around the choke system. It might also prove useful to investigate/renew the rubber plugs over the idle jets, replace the petcock vacuum line, maybe even investigate the choke mechanism, seals, etc. Something somewhere ain't right and is letting in air. Somewhere.


Great photos, by the way. All you shaftie owners, take heed! Split your airbox, seal it, and enjoy the fine carburetion your machine was built to deliver.

[Redman]

I discarded the now-useless rubber seal and used self-stick foam weatherstripping to seal between the halves, just the same as on the side covers. 'Twasn't rocket surgery.

Sealing the airbox halves will do you some good, but your idle problem is probably unrelated to this.
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Thanks Brian.

Yep, have used the weatherstriping before on the side panels.
(If anyone has further interest in the subject of sealing the air box end covers, they can see that in the background of one of the photos above in post #2.)
Advantage of using weather stripping between the air box halves is that the halfs could easily be taken apart again. I suspect the warp in my upper air box half is more than one thickenss of weather sripping can take up. ANd if weather stripping too thick, and there is only four screws holding the two halves to gether- wonder if it will cause the plastic of the top half to warp more - again - even further. And I dont see much need for ever taking box halves apart - so, maybe will concider using adhesive-sealant such as Automotive Goop. That is what I have holding the snorkle in place.

Oh, I just remembered, and I have another air box around (that I got the snorkle from). Will see if its top plastic part is in better condition.

Okay - so this airbox leak between the halves is a problem, but not cause the high idle symptoms.

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Sealing the airbox halves will do you some good, but your idle problem is probably unrelated to this. You have an air leak and/or a clogged passage somewhere in the carbs or possibly a remaining leak in or around the intake boots (I know these are all-new parts).
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Let me ponder/study each point that you mentiuoned.

Hum .... okay.
Intake boots... maybe not installed properly (are new, new orings, new clamps). WIll look that over.

Petcock vacuum line ... can visually check that. Maybe pinch off and run petcock on prime, as a test.

Clogged port/passage in carb. Hum, that is something a lot different than an air leak.

Need not suspect the petcock itself, right? I undeerstand that if problem with the petcock diaphram, that is will suck gas into cyclinder, not extra air. Correct?

Plug over idle jets .... that is the rubber plug inside the bowl, correct. I replaced those last year or maybe year before. Hum, I had thought that would be under the gas level, so maybe you are refereing to something else and my ignorance is limiting my understanding of what you are suggesting.

Oring around idle mixture ... that the adjustment what can see on top - foward part of carb? THose orings were replaced this January. I could test that idea by holding finger over that opening were the adjumnet screw is, correct?

O-rings around choke system. Hum, will have to look into that. I did get an a RobertBarr o-ring kit in January. But carbs looked good (as appraised by Tim, Joe, Greg) so only replaced the one around the idle mixture (air screw?).

Will investigate further.

Thanks,
Dave

[Johnny Drummond]

Hi Redman, Johnny here( he of the "interesting" carb boots).Take a good look at your diaphragms-a really good look, my wife bought a GS550 with the same problem and I spent weeks trying to fix it I did all the things you have with the same result and as a last resort I looked at the diaphragms 1 and three had the tiniest of holes where the carb tops clamp them down-just wear and tear on a bike that had less than 30,000 miles on the clock. I got good ones from a set of GS650 carbs which cost $35 from a local wrecker and the kittle bike hasn't missed since(5 years) ,a mate of mine spent ?200 on work to fix an identical problem and was without his bike for 3 months for it to come back in the same state after 60 miles-turned out the "mechanic" hadn't even changed the inlet boots just rubbed black silicone gasket over them so he rang me as the only other person he knew who had a GS.I took the carb tops off and found identical damage in no.1 and no.4 diaphragms and less but still some damage in the other 2 I also saw straight away that the inlet boots were cracked, so he had to pay even more money in parts and I fitted them in an afternoon( for a pack of cigarettes!)however he could only afford to replace the worst diaphragms and now has the idle set so low (so it won't rev through the roof) that he has to gently rev the bike at rest hope that this helps you

[raistian77]

O-rings around choke system. Hum, will have to look into that. I did get an a RobertBarr o-ring kit in January. But carbs looked good (as appraised by Tim, Joe, Greg) so only replaced the one around the idle mixture (air screw?).

When it comes to carbs this tends to mess everything up. Carbs can look beautifull and still be bad. On the VM carbs the pilot mixture screws can suck air if the orings are not sealing. The hanging rpms are coming from air being introduced that the carb can not or is not compensating for.

I am rebuilding a set of CV carbs for a Yamaha Venture. Rather than fight it, I ordered all new diaphragms, after-burn diaphragms, new gaskets and o'rings. Its not worth fighting a running issue that may be a simple as a new set of diaphragms and orings.