Carb-airbox boots won't stay on?

[longranger44]

Maybe this has been covered extensively here but thought I'd post. I noticed that the rubber boots that attach the air box to the rear of the carbs on my 82 gs750 wouldn't seat fully just from pushing the box forward. I could push them forward and try to tighten the clamps at the same time but they would inevitably slip back off. Took the air box out and noticed that the boots were not even, the two in the middle of the air box in particular were caved in. Detached them from the air box and it became obvious the plastic of air box was warped from age or heat or whatever.

So my solution was--stack some sockets/washers up inside the air box to spread the plastic until the holes are even and then heat up that wall of the air box with a heat gun to re-form the plastic. Here's a pic to illustrate what I did, figured I'd post it in case it might help someone out who has the same issue.

 

[chuck hahn]

Yes the plastic seems to dish in over time. Ive done this to every plastic box ive ever dealt with . Outer ones seat normally but two inside ones wont.

 

[longranger44]

Yes the plastic seems to dish in over time. Ive done this to every plastic box ive ever dealt with . Outer ones seat normally but two inside ones wont.

Yep exactly. It's really not a great design because there is zero support in the middle of this large plastic box. A couple of abutments in the middle would have prevented that, surprised the Japs didn't think of that they seem to think of everything else.

 

[Sandy]

Yep exactly. It's really not a great design because there is zero support in the middle of this large plastic box. A couple of abutments in the middle would have prevented that, surprised the Japs didn't think of that they seem to think of everything else.

Thanks for tip. My GS1000 airbox fits a bit funky so this winter I'll check that out. As for the Japs not thinking about it I don't I think they thought we be riding these things 40-45 years
later. LOL

 

[longranger44]

Thanks for tip. My GS1000 airbox fits a bit funky so this winter I'll check that out. As for the Japs not thinking about it I don't I think they thought we be riding these things 40-45 years
later. LOL

True lol. If they didn't want that then they shouldn't have made them so damn well!
another little tip, I used my heat gun on its hottest setting but make sure to keep it moving so it doesn't heat up any one area too much, if it starts to turn shiny it's too hot.

 

[chuck hahn]

And use a hammer handle or big screwdriver grip to push the wall forward from the filter side. Hold till it cools sufficiently or dunk it in a bucket of water to reset the shape

 

[jdub6092]

I just got done doing this for the third time. The first time took nearly all day and I still may have had a leak.

Just recently did rounds two and three and it went fairly quick, so I'll share what worked for me.
Obviously, you need to remove the battery holder, then loosely attach the screws that hold the filter cage mounting brackets to the air manifold/plenum.
Next make sure that the dots on the outer boots are adjacent to the dots on the manifold.
On my manifold, one of the center boots has some play to help alignment to the carb. See if yours will move left/right. Maybe stuck?

I then put a bit of dielectric grease (what i had available) on the inside/outside edges of both the carb and manifold boots.

Next, insert the carburetor all the way in at the cylinder head boots. You should now have some space between the manifold boots and the carb.

Tilt the carbs slightly down and the manifold slightly up to make initial contact. Adjust the one center boot to line up

Next use a heat gun the soften up the boots. You won't have 360 access, but hit all sides on the top and whatever you can on the bottom.

Finally start the back and forth movement of carbs and manifold until they are inserted. I only had to rock the manifold up and push forward. Getting the initial alignment is the key.

This is just the method I came up with and it worked for me. Best of luck!

 

[longranger44]

I just got done doing this for the third time. The first time took nearly all day and I still may have had a leak.

Just recently did rounds two and three and it went fairly quick, so I'll share what worked for me.
Obviously, you need to remove the battery holder, then loosely attach the screws that hold the filter cage mounting brackets to the air manifold/plenum.
Next make sure that the dots on the outer boots are adjacent to the dots on the manifold.
On my manifold, one of the center boots has some play to help alignment to the carb. See if yours will move left/right. Maybe stuck?

I then put a bit of dielectric grease (what i had available) on the inside/outside edges of both the carb and manifold boots.

Next, insert the carburetor all the way in at the cylinder head boots. You should now have some space between the manifold boots and the carb.

Tilt the carbs slightly down and the manifold slightly up to make initial contact. Adjust the one center boot to line up

Next use a heat gun the soften up the boots. You won't have 360 access, but hit all sides on the top and whatever you can on the bottom.

Finally start the back and forth movement of carbs and manifold until they are inserted. I only had to rock the manifold up and push forward. Getting the initial alignment is the key.

This is just the method I came up with and it worked for me. Best of luck!

If the airbox is warped like mine was there's no point in even trying to install the boots, you'll just drive yourself crazy and even if you get them all on they'll eventually pull off again. Fix the airbox like I outlined in the 1st post and everything will fit together easy like it should

 

[Nessism]

The heating trick sounds like a good one. The kitchen oven could be used, although it may well stink up the house...

I'm NOT a fan of using grease inside the boots where they seal to the carbs. That will just make them want to slip back out.

What I do is to position the airbox in the frame, but don't bolt it down. Then get the carbs in place, between the head boots and carb boots. Next, push the airbox forward, onto the back of the carbs, and tighten down the clamps. Last step, push the carbs with airbox, forward, into the head boots. Before tightening the clamps, bolt the airbox to the frame, holding everything in place.

 

[longranger44]

The heating trick sounds like a good one. The kitchen oven could be used, although it may well stink up the house...

I'm NOT a fan of using grease inside the boots where they seal to the carbs. That will just make them want to slip back out.

What I do is to position the airbox in the frame, but don't bolt it down. Then get the carbs in place, between the head boots and carb boots. Next, push the airbox forward, onto the back of the carbs, and tighten down the clamps. Last step, push the carbs with airbox, forward, into the head boots. Before tightening the clamps, bolt the airbox to the frame, holding everything in place.

If yours is bowed in as bad as mine was, all the finagaling in the world won't work and I wouldn't trust them not to slip off later as the box is trying to pull the boots off constantly. 100% agree about the grease, no need for it if everything lines up correctly and the rubber can't grip the aluminum as well when clamped if greased. I thought of the oven but didn't want the smell and wanted to more closely monitor the heat and only heat the areas needed.
​

Using the big socket and stack of washers to spread it open was the real game changer for me because it let me micro adjust the amount of spreading by just adding/removing washers and more importantly held it there while I heated it and let it cool. I tried just pushing it into place by hand but trying to heat it and then let it cool all the way while holding it exactly where it needed to be was a pain.

 

[first timer]

My Kat air box had metal collars pressed into the inside of the air box boots, those metal collars then sandwiched the the boot hard against the air box hole ID holding the boots firmly. Did the 750 or any of the 1100 do that too?

I ask cause I was going to replace my boots with fresh ones but quickly determined it was going to be very hard and likely damaging if I tried to remove those metal collars put new boots in and reinstall new collars.

 

[bwringer]

My Kat air box had metal collars pressed into the inside of the air box boots, those metal collars then sandwiched the the boot hard against the air box hole ID holding the boots firmly. Did the 750 or any of the 1100 do that too?

I ask cause I was going to replace my boots with fresh ones but quickly determined it was going to be very hard and likely damaging if I tried to remove those metal collars put new boots in and reinstall new collars.

I believe most, if not all, GS models used metal spring collars like that. They're a pain to deal with, but it's do-able. You have to compress and pry the collars in a little bit so you can push them past the indentation inside the boot and pull them out. And you have to compress them to get them in. A hose clamp can help. They're not inserts, they're springs, a little like piston rings; you won't hurt anything. You'll get the knack after wrestling with the first one for a while.


I've had to re-shape several GS airboxen with a heat gun -- I absolutely would NOT heat up the entire airbox. You need the rest of the airbox to stay relatively stable while you're straightening the rear (or front, if needed).


One added tip: On the 1100E, you can make battery access about 1,000,000% easier by heating one corner of the rear airbox and pushing it in. I don't remember which corner, exactly, but it's the corner that interferes with the frame and keeps you from removing the gaddurn thing, and will probably have a lot of scuffs on it. If you know, you know.

Just get it somewhat hot, hold it at a 45 degree angle, and push it against your bench to blunt the corner about half an inch. This will make zero difference to its function, but will make the bike much easier to work on.

 

[first timer]

I believe most, if not all, GS models used metal spring collars like that. They're a pain to deal with, but it's do-able. You have to compress and pry the collars in a little bit so you can push them past the indentation inside the boot and pull them out. And you have to compress them to get them in. A hose clamp can help. They're not inserts, they're springs, a little like piston rings; you won't hurt anything. You'll get the knack after wrestling with the first one for a while.


I've had to re-shape several GS airboxen with a heat gun -- I absolutely would NOT heat up the entire airbox. You need the rest of the airbox to stay relatively stable while you're straightening the rear (or front, if needed).


One added tip: On the 1100E, you can make battery access about 1,000,000% easier by heating one corner of the rear airbox and pushing it in. I don't remember which corner, exactly, but it's the corner that interferes with the frame and keeps you from removing the gaddurn thing, and will probably have a lot of scuffs on it. If you know, you know.

Just get it somewhat hot, hold it at a 45 degree angle, and push it against your bench to blunt the corner about half an inch. This will make zero difference to its function, but will make the bike much easier to work on.

Thanks for the tips Brian, my boots weren't bad so just cleaned everything up. I will print out your note however and stick it in the my parts bin next the new boots if i need to do this down the road.

Miss riding with you and the gang, if you find yourself in Tucson I'll dig up a bike for you.

 

[roy826]

I used the heat gun method on my 82 Kat 1000 air box. It worked somewhat ok. They were all level on the work bench but as soon as I started installing carbs I could clearly see the inside two were not as level as on the tabletop, not sure what happened. Either way they are mostly up on the carb throat ends better than before and I checked for leaks and there were none, carbs sync’d up fairly easy if you can call that procedure anything but easy.

 

[longranger44]

I used the heat gun method on my 82 Kat 1000 air box. It worked somewhat ok. They were all level on the work bench but as soon as I started installing carbs I could clearly see the inside two were not as level as on the tabletop, not sure what happened. Either way they are mostly up on the carb throat ends better than before and I checked for leaks and there were none, carbs sync’d up fairly easy if you can call that procedure anything but easy.

Did you let the box cool completely before checking it for straightness? I had to do it a few times and stack more washers until that front wall of the air box was actually bowed out a bit. Then after it cooled it was straight despite looking convex while heating it with the stack of washers spreading it.

Basically I had to go past straight while forming it for it to end up perfectly straight after it was cooled and the washers removed. Kind of like bending a piece of metal you have to bend it past where you want it to end up. Hope I'm explaining it clearly.

But no matter, if you got all the boots to stay on it sounds like you got it close enough.

 

[roy826]

Did you let the box cool completely before checking it for straightness? I had to do it a few times and stack more washers until that front wall of the air box was actually bowed out a bit. Then after it cooled it was straight despite looking convex while heating it with the stack of washers spreading it.

Basically I had to go past straight while forming it for it to end up perfectly straight after it was cooled and the washers removed. Kind of like bending a piece of metal you have to bend it past where you want it to end up. Hope I'm explaining it clearly.

But no matter, if you got all the boots to stay on it sounds like you got it close enough.

Yes I let it cool and it looked level on a table laid boots face down. It’s better than it was before but certainly not perfect. I checked for leaks with it running and none were found so it’s at least sealed up on the inside two cylinders now.

 

[longranger44]

Yes I let it cool and it looked level on a table laid boots face down. It’s better than it was before but certainly not perfect. I checked for leaks with it running and none were found so it’s at least sealed up on the inside two cylinders now.

That's good. Probably not possible to get it perfect but the boots give a little margin for error. If it's not leaking then it sounds like you're good to go.

 

[Wingsconsin]

Sorry the sound is so bad ..but this could help someone..
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