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An air filter design

Daren

Daren
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Hello everyone, I was frustrated trying to get some filters for my 76' F1 Supersport. The bike came with grungy K&N pods which were actually too big so the previous owner had shimmed them with rubber to make them fit. Not really what I wanted for my bike. After searching for something reasonably affordable, but somewhat custom, I came up empty. So I figured I'd just make my own. The image below shows the parts. Backing plate, pods, bottoms of 24oz. beer cans, an aluminum plate, and nuts and bolts and screws.
Obviously if you have access to CNC and CAD you can make the mounting plate out of aluminum, but I only have hand tools so mine is made out of heavy duty vinyl.
filter 1.jpg

This is what they look like assembled.
filter 1a.jpg
filter 1b.jpg

I got some cheap pods and cut them down, put some copper screen in the bottom and foam on top of the screen.
filter 2.jpg
filter 2a.jpg
filter 2b.jpg

Drilled some holes in the back of each pod to mount them to the backplate.
filter 3.jpg

Cut the bottoms off some 24oz. beer cans which polish up nicely.
filter 3a.jpg
filter 3b.jpg

cut some brass tubing as standoffs for the top plate.
filter 3c.jpg

and bob's yer uncle. The fact that they are one unit does not make them that much harder to attach.
I can adjust the airflow by stuffing or un-stuffing more foam to get the right balance for my jets and exhaust.
I know many will say "stock air box is the only way to go", but the bike came re-jetted so I need to experiment to find the right balance for what I already have. One good thing about the heap I bought is it came with clean carbs, no varnish or crud anywhere, so I'm leaving them alone until they need attention.
Hope you like it, feel free to copy, unless you copy them for sale,
then I'll come after you for a cut....ha, ha.
Daren
 
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Thank you, necessity is the mother of invention. But as most designs go I already want to do some changes, so it's a work in progress. What do you think of my assumption I can tune the filters to the bike, have any advice? Here is what they will look like on the bike.

filters on carbs.jpg
 
I wouldn't restrict airflow to correct jetting...all you are doing is losing power. you need to jet to the engine, exhaust and intake not restrict things to use the jets that are in there. It very well may have been "rejetted" but if it was still rich or lean then it wasn't re jetted with the correct size jets for what the engine needed. If you are restricting things to correct jetting then you are just masking the problem and losing performance and rideability.
 
I fully agree with Digger, proper jetting is paramount for performance. I was only stateing that air flow has a direct effect on fuel mixture, sorry for any confusion.
 
Thanks to all for the remarks and advice. I'm assuming the previous owner had things set up so the bike was at least usable. I only had a chance to kick it over to insure it ran, but the bike was not road worthy so the best I could do was rev it up in place. At least at idle and lower RPM's the bike was smooth, no sputters, no lag. He had oil drenched pods, judging by the sooty exhaust ports he was probably running rich. I'm not a racer, for now I only want the thing to run without dropouts and dead spots. The fact that I won't be at optimum performance is rather redundant...the motor most likely needs valve work and probably rings soon. The quest for a monster machine which blows everyone off the road with the most HP is not what this bike will be about. As much as I would like to re-do the engine, that will have to wait. Therefore I want to wait to tune the carbs to the "new" engine. For now I must go with what I have. Obviously I will know more once I get it running again. Final question.....any advice on filter material other than foam? I was thinking coffee filter paper.
 
Hi all,
I would like to update this post with my experiences in case it can help others with similar problems. The pods I used for the filter design were cheap, $20 for 4. Although I did get the bike running it wasn't quite right. Remember I bought this bike already jetted for pods so I assumed using pods for my filter design would be fine. No matter what I did with the air/fuel mix screw the bike ran like it was old and tired. Finally I decided to take my filter off and run the bike with naked carbs and oh boy did the bike scream. Looking closer at the cheap pod boots I noticed they have an opening about 25mm wide leading from the pod to the intake, even though the boot is 40mm to fit the carb.

new filter 1a.jpg

This restriction combined with the proximity of the inner flange to the intake port was causing airflow issues.
So I had to redesign the filter with a coupling which is 40mm front to back.

new filter 2a.jpg

Essentially these are velocity pods.

new filter 3a.jpg

So if you are running cheap pods and have air/ fuel issues check the boots and try running the carbs naked.
 
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