Stock airbox vs. Pods vs. Make it on me own

[Marvey]

I'm bringing a '79 GS850G back out of the grave. Many thanks to all who have helped me along the way in the past week or so. Couldn't tell ya how helpful you've been, between the info on the site and the advice from you guys, This thing is rolling smoothly towards the road.

I'm facing another problem with this GS850 Frankenrat: The airbox. The OEM box is hammered, and MIGHT be fixable, but I'd rather not. Here's why.

I'm a sheet metal guy, and there's a thousand pounds (understatement) of sheet metal boxes, half boxes, boots, collars, elbows, stock flat, etc. etc. just laying around waiting to be used for something. Given the supply of possible replacement material and the expertise, tools, etc. relating to said, I'd rather make a new box in 20 minutes than rehab the old one in 6 hours plus various costs. (JB weld, caulking.. I'm pinching pennies here in ways I never have before.) Not to mention the weight savings of 26 gauge vs. factory airbox. It's a lot.

Keeping in mind the role intake manifold vacuum and air volume play in proper operation of the vm26ss, my questions are:

#1: Should I build a box, duplicating in every possible way the characteristics of the OEM box (Two chambers, same size air inlet, might accidentally forget the ol' regurgitative PCV, etc) using said materials and expertise
OR
#2: I am under the impression, from information on this site as well as other sources that pod type filters work very well with Mikuni Flat Slide carbs. VM26ss are not flat slide. Is there a lot of difference, in this particular arena, between flat slide MICs and "cylinder slide" vm26ss Mics? I would be making the pods with 'UNI' brand filter stock and previously mentioned sheet metal reserves. No money for K&N, no love for JCWhitney.

Thoughts?

A thousand thanks in advance.

[tkent02]

Thoughts?

No brainer. Build a better airbox.

[max parsons]

I spent way too much time trying to tune my vm26 carbies to run with unifilters and got nowhere.I have just fitted k+ns and a dynojet kit and in no time at all I had The Dirty Old Pig running better than it ever has.Spend the dollars.

[silverhorse47]

If you are happy making things work and understand the fundamentals....engine vacuum and back pressure, I would love to see you make your own. My own project air filter(s) are made with plumbing parts and furnace filters, but the rebuild has yet to be fired up. To my way of thinking, the main thing is to be able to increase or decrease the amount of air going to each carb if the filter itself is not a known quantity. You have to be able to adjust the amount of air as well as the amount of gas going to each carb if you are running individual filters.
If you are making an air box, the factory has already figured this out for you, and if you have the materials to fabricate a box that can duplicate the exact airflow to your cylinders, I see no problem with your plan. Try to build in a way that allows you to increase/decrease the quantity of air.
I did it by making a rotating sleeve over a round tunnel that encloses a bit of filter material. By drilling holes through both, and countersinking them, I can adjust the airflow to each cylinder in fine degrees by just turning the outer sleeve.
If you incorporated this idea into one filter box, you could increase/cut down the amount of air going to the engine by turning the outer sleeve.
Perhaps this will help fine tune your final result.
Good luck,
S.

[Marvey]

If you are happy making things work and understand the fundamentals....engine vacuum and back pressure, I would love to see you make your own. My own project air filter(s) are made with plumbing parts and furnace filters, but the rebuild has yet to be fired up. To my way of thinking, the main thing is to be able to increase or decrease the amount of air going to each carb if the filter itself is not a known quantity. You have to be able to adjust the amount of air as well as the amount of gas going to each carb if you are running individual filters.
If you are making an air box, the factory has already figured this out for you, and if you have the materials to fabricate a box that can duplicate the exact airflow to your cylinders, I see no problem with your plan. Try to build in a way that allows you to increase/decrease the quantity of air.
I did it by making a rotating sleeve over a round tunnel that encloses a bit of filter material. By drilling holes through both, and countersinking them, I can adjust the airflow to each cylinder in fine degrees by just turning the outer sleeve.
If you incorporated this idea into one filter box, you could increase/cut down the amount of air going to the engine by turning the outer sleeve.
Perhaps this will help fine tune your final result.
Good luck,
S.

I am VERY interested in what you have to say brother. Are you a plumber?

Can you elaborate, maybe with an 'MSpaint' diagram, or such RE: rotating sleeve over a round tunnel, etc.

I'm having trouble seeing in my mind what you mean, as happens often in construction (sounds like you have a background there)

Please elaborate, all the way. And if you make a mistake, I'll just hit you on the head, like any good tin-knocker.

Seriously though, explain. Much appreciated.



If you're not a plumber, disregard my verbal abuse. It's the nature of things.

[SqDancerLynn1]

I'm too tired to look right now but a year or two ago someone here made their own filter using uni air filter foam & using the stock air cleaner boots. Had very good results

[Nessism]

Just go to ebay and buy a used airbox. Done. $45 delivered http://cgi.ebay.com/ebaymotors/Airbo...4506.m20.l1116

Trying to make an airbox sounds like folly. Focus on more important things like properly rebuilding the stock carbs and getting them synced properly.

[tkent02]

Just go to ebay and buy a used airbox. Done. $45 delivered

What fun is that?

[Nessism]

What fun is that?

The fun starts when you kick back in your garage chair, crack a beer, and admire your beautiful, properly running bike.

[Big T]

The fun starts when you kick back in your garage chair, crack a beer, and admire your beautiful, properly running bike.

As it cools off just after you've returned from a nice ride!

[crag antler]

The fun starts when you kick back in your garage chair, crack a beer, and admire your beautiful, properly running bike.

I kick back in my garage chair and I would freeze my bys off.
It's like 28F but they say it feels like 19F. I ain't that stir crazy yet.
Soon though

[crag antler]

Sorry for the hijack there, but if you have the material,talent and time,why not do a custom made airbox??
See if you can use your OEM as a base model and improve off of that.
Maybe a side induction set-up ???

[drhach]

Just to chime in, it he shape is not too important. What matters most is volume and inlet size. If those two are the same, the bike shouldn't run any different. Both of those factors are pretty easy to copy, so, why not. You actually could make an airbox that is hidden a little better than the stock one. One other issue that you might encounter is noise. With the metal panels there is the drum effect. That may or not matter to you. You could always line it with something or make it double walled, depending on how good you are. I say go for it.