How does the filter seal to the airbox??

[DannyMotor]

78' GS750, refinishing the airbox and trying to install the filter, I notice there's a HUGE gap between the top of the filter and the bottom of the upper housing.

I wiggled the filter around a bit and bent the screw hole bracket a bit and I can get the filter fitted REALLY close, but there's still a gap. That, and it looks that the brackets that hold the tabs are almost twice as wide as the tabs themselves.

Any hints? Is there a gasket that I'm missing?

You can see why this concerns me right? Haha. I don't want to sound like I'm making a big deal over nothing, but if the filter won't seal... then air will just go around the filter rather than through it. Which will suck...

Thanks!

 

[keman]

There's supposed to be a foam gasket attached to the filter frame.

 

[DannyMotor]

Well that would've been the goopy mess that fell apart when removing the old filter... awesome.

What should I do? Just buy a cheap UNI filter, or filter foam of sorts and cut a 'gasket'? Doesn't show up on any parts manifests.

 

[7981GS]

Clean all of the old rotten foam crap off and get the surface where it was clean with brake cleaner.
Take a tube of RTV, one of the only things that it is good for, and form a thick bead where the foam was.
Let it dry, in the Sun is best, for at least 15-24 hours and it will form a leak-proof seal that will not crumble like the factory foam.


Eric

 

[DannyMotor]

Eric, that is brilliant! Will do! How thick? 1/4 inch?

 

[7981GS]

10-4.
Let it dry hard. As in, hard rubber seal.
Make certain that you make it tall enough to be compressed when it is installed and A complete/tight fit.
In other words, make one long bead with no gaps.

Eric

 

[DannyMotor]

And you recommend doing this IN the airbox itself, and not on the top bracket?

 

[Steve]

One modification to the RTV seal: put a healthy bead around the filter opening, make sure it is tall enough to span the gap. Place some Saran Wrap (or other food-wrap film) over it, then put in in place. Do not tighten the mounting screw all the way. Let the RTV set up, then remove the filter and remove the food wrap. You will have a perfectly-formed seal that has not stuck to the housing. When you re-install the filter and tighten the mounting screw, it will provide the seal that it needs.


Anothe option is to go to the hardware store and get some stick-on foam insulation. Quick, easy, cheap.

.

 

[7981GS]

On the filter cage.
I can find one or two tomorrow to take a pic of.

Eric

 

[bwringer]

Anothe option is to go to the hardware store and get some stick-on foam insulation. Quick, easy, cheap.

.

Yes, this. Use stick-on weather stripping, then put a thin coat of grease on the weather stripping so it can slide into place and doesn't weld itself to the box.

 

[chuck hahn]

The PROBLEM with RTV and letting it dry is this. If you dont get it perfectly flat and of a consistant thickness youve got air gaps anyways, which defeats the intentions. Get some 3/8 thickX 1/2 wide stick on waethersripping and cut and paste it around the top of the filter rack. Its easy to remove when it gets worn out and easy to replace.

 

[DannyMotor]

Thanks for the help guys! I think tge weather stripping and grease is the way to go for me.

 

[BassCliff]

Hi,

I use weatherstripping.

Thank you for your indulgence,

BassCliff

 

[Steve]

The PROBLEM with RTV and letting it dry is this. If you dont get it perfectly flat and of a consistant thickness youve got air gaps anyways, which defeats the intentions.

That is why I suggested using the Saran Wrap so you could put the filter almost in place to form the RTV.
Using the Saran Wrap keeps the RTV from sticking to the filter housing so you can pull it out and trim out the hole in the middle.

The weatherstripping is quicker and easier (that's the way that I did it), I was just following through with the RTV idea.

.

 

[7981GS]

Engineers look for better solutions to the cheapest possible factory solutions.

The word engineer is derived from the Latin roots ingeniare ("to contrive, devise") and ingenium ("cleverness").

As always, do what ever suites you.



Just sayin'


Eric

 

[old_skool]

If done right, I'm sure the RTV method would be best, but with that said, I used the adhesive foam as well, 1) ease of making 2) comes in a package where you can make more in the future 3) it works!

 

[bwringer]

RTV breaks down and crumbles in the presence of gasoline vapors, so it is not suited for long-term use on the air filter.

Weatherstripping (believe it or not) holds up fine. And it's soft, so it forms a better seal.

The photo Basscliff posted shows how to use weatherstripping to seal the filter. Shaftie owners also need to seal the chrome covers on the sides of the airbox in the same way.

 

[DannyMotor]

I bought the 3/8ths by 1/2" stick-on stripping. Stuck it to the top of the filter holder, oiled the ba-jesus out of it with some K&N spray-on oil... and slid it right in.

Fits perfect! No gaps, nice and tight!

It was only 4 bucks for 10 feet... so I'll just swap it out every time i clean the filter.

On a plus note... Ran the bike for the first time with the air-box on it... HOLY HELL, so much smoother, throttle is almost 'snappy' and the idle is more stable. Note that the bike is still just a frame and motor right now... but the difference is amazing. HUGE props to the bench-balance tutorial, BassCliff! It seems I won't have to fiddle with the carbs too much other than the mix screws.

 

[chuck hahn]

Remember that a bench sync is just that..an eyeballing to get them somewjhat close enough to start and run relatively well. Wait till you throw the guages on her to get them pefect..thats when she will settle in and really run smoother than it is now.

 

[old_skool]

Ran the bike for the first time with the air-box on it... HOLY HELL, so much smoother, throttle is almost 'snappy' and the idle is more stable.

We need to use you as the "Poster Boy" for new to them GS owners who can't figure out why their bike runs like crap after first buying it and before getting anything properly done, they start hacking at the airbox, or throw a quick set of cheapo pods and cut the exhaust down...etc...

And don't forget Bwringer's airbox side cover mention, seal them up as well.

Your doing exactly what needs to be done even if someone was to change to pods later, getting the bike to run properly for a baseline before any modifications. Stay on track, you'll be more than pleased with the results and what you can accomplish!:clap: