How To : Air Filter Relocation For Big Carbs

Air Filter Relocation For Big Carbs Or Tight Clearances

I had a clearance issue with my air filter and a big carb. Since I'm cheap and my K&N is pretty much new, I wanted to make it work instead of spending $30-40 on a new filter. I also like the shileding on the K&N. Some of the other shielded filters I have seen look like they would trap moisture in with the filter if you aren't able to mount them facing/angled up. Here's the info for anyone else that runs a bigger carb or just has clearnace issues. Some sizes may vary depending on carb setup. My carb uses a 39mm filter and I had a 39mm filter.

Materials
Air filter with 39mm or 1 1/2" opening

3/4" 90 degree PVC elbow (could be another type of 3/4" coupler, this was cheap) $0.39


J-Trap 1 1/2" or 1 1/4" tubular to 1 1/2" tubular w/clamps $8.49


The J-Trap took me a bit to find. I looked in a couple of local hardware stores for suitable materials before finding it at ACE Hardware. ACE Part Number : 4126041

I started by measuring the depth of my carburetor's mouth and cutting the J-trap as pictured to leave about 1/8" more than that measurement to get the most clearance. You should be able to cut it with a good pair of scissors.


Now the ridge that normally holds a hose clamp in place is in the way, so I shaved it off with an x-acto knife.


After some test fitting and trial and error I marked and cut the J-Trap to the length that suits my application.


It's not a great idea to clamp an air filter to a rubber hose, so I cut 5/8" to 3/4" of a straight section out of the 3/4" PVC coupler and put it in the J-Trap. The 1st image is just to show that even though it's marked as 3/4" the couplings are actually over 1" inside diameter.




Then I stuck the air filter on the end and clamped it in place. If you use a shielded filter, or any filter that needs to sit a certain way, be sure to check orientation before tightening the clamp.


Of course the final step is to attach it to the carburetor and make sure everything is secure.


It's nothing special, but very cheap and easy if you already have a filter. This setup makes quite a loud midrange tone. I like the sound, but it's probably not a great idea if your scoot is quiet.