Airbox, rubber piece on the inside covers?

[Guest]

I'm rebuilding a 79 GS850GN, and I'm playing around with the airbox. On the inside of the chrome covers is a flat rubber piece that covers the entire inside. I can't find the part number on the rubber, and I don't see it in any part diagram. One of the pieces is falling apart, and I can't find it on ebay either. Does anyone know what this is? I'm new to the biking world and have no idea if I need it or not. Thanks in advance for your advice.

[bwringer]

Yes, you need it -- on a GS850, the airbox must only draw in air where it's supposed to, through the rubber snorkel on the back and the vent at the bottom, not from leaks elsewhere.

Fortunately, the solution is easy, cheap and simple -- just get some self-adhesive foam weatherstripping, clean up the inside of the airbox lids so it'll stick, and install pieces of the foam weatherstripping. I usually cut the ends at a 45 degree miter so the ends will seal.

Others have used other foam materials with success. The weatherstripping is the simplest.

You also usually need to apply the weatherstripping to the top of the air filter cage so it can't draw in dirty air. This seal is usually also missing from elderly airboxes. I usually add a coating of grease to the foam so that the metal filter cage will slide into place in the airbox easier.

If the foam air filter is crumbling, you might need a new Uni filter element (don't throw out the cage).

Sometimes some PO has installed a K&N filter in place of the stock cage and oiled foam; you can get cleaning kits at any auto parts store if it's in decent shape. Make sure it seals correctly too.

[ChrisMA]

I've recently sealed my GS1000G airbox (which I think is the same as yours), twice. On my first attempt, I applied weatherstripping around the inside of the airbox openings, and along the filter area, as shown here: http://gsarchive.bwringer.com/cbsaun...ox-sealing.pdf I kept the rectangular top half of that rubber gasket/seal thing, and replaced the bottom part with weatherstripping. I still couldn't get it to idle reliably, and it ran really lean (especially on 1&4).

I then went back and added some additional stripping around the inside of the covers, and jammed the whole thing back together (was REALLY tight), and my air leak issues appear to be gone. There's a picture of where I'd added the additional seal along the covers here http://gsarchive.bwringer.com/cbsaun...ake_repair.pdf (page 14).

I also noticed that the top section of that original rubber seal was a bit warped with age, and had folded back where it should have had a tight fit along one of the metal ridges. I added some silicone around the inside to hopefully seal that up.

[mascottjd]

ChrisMA, thanks for your info. Your pics show me exactly what I'm experiencing with the rubber gasket/seal on the inside of my airbox covers. Just to be sure, should I keep the tops of the rubber seals shown here? They don't seem to be as thick as yours, and I don't have a top part of the airbox, above the filter... Should I? IMG_2018-08-13_17-59-13.jpg

[mascottjd]

"You also usually need to apply the weatherstripping to the top of the air filter cage so it can't draw in dirty air"

Bwringer, thanks! Do I need to cover the entire top of the air filter cage? I'm not sure I quite understand. And should I use the same type of weatherstripping that I'm using on the inside of the covers?

[Dogma]

Not the entire top of the filter cage, but the entire perimeter of the filter cage. And yes, you should be able to find weather strip that works in both places. I think I used 1/4" closed cell foam.

[ChrisMA]

Glad to help, though those weren't my pics, I've just gone through the rebuild process a few weeks before you I'll try explaining, but I think it will all be clear if you follow the guides linked above.

The black seals pictured in your airbox cover, are they loose, or are they stuck to the chromed cover itself? If they're stuck, you'll want to get them unstuck and apply them to the airbox itself. Then you'll apply the weatherstripping, and only put the covers back on last.

The piece you'll want to try to salvage is the top, rectangular section. Look at the pic at the top of page 9 here: http://gsarchive.bwringer.com/cbsaun...ox-sealing.pdf The picture right below it then shows where you'll apply the weatherstripping around the perimeter. In addition to that, I ended up having to add more stripping around the inside of the side covers themselves (which is that first pic I'd referenced).

Also, in the photo you'd posted, I see that you have some warping around the outside of that rectangular piece; mine did as well. When you put that back on to the airbox, look at it from inside of the box and see how tight it looks. That's where I'd had to add some extra silicone.

[mascottjd]

Not the entire top of the filter cage, but the entire perimeter of the filter cage. And yes, you should be able to find weather strip that works in both places. I think I used 1/4" closed cell foam.

Thanks Dogma!

[mascottjd]

Glad to help, though those weren't my pics, I've just gone through the rebuild process a few weeks before you I'll try explaining, but I think it will all be clear if you follow the guides linked above.

...

Also, in the photo you'd posted, I see that you have some warping around the outside of that rectangular piece; mine did as well. When you put that back on to the airbox, look at it from inside of the box and see how tight it looks. That's where I'd had to add some extra silicone.

Thank again, Chris...worked perfectly!