Rebuilding a Honda CB360 Air Filter

How To Rebuild a 1974 Honda CB360 Motorcycle Air Filter

The stock air filters on the CB360 were meant to be replaced as a unit, metal casing and all. The actual filter paper is glued to the casing and rubber fairing that attaches to the carburetor. In other words, keeping the filters clean requires a costly purchase of antique parts that are not manufactured any more.

But I succeeded in replacing the filter paper with a section of modern automotive filter. This technique also simplifies future filter changes, allowing you to retain the original casing and rubber fairings, and avoid hunting down aged replacements that are themselves less effective.

Needed Materials

• the old filter assemblies (there are two)
• silicone sealant
• a new accordion paper filter (I used the FRAM CA3681)
• hammer and sharp chisel
• heavy-duty scissors, shears, or similar cutters
• several heavy books, or clamps
• something to drink (this may take an afternoon)

Preparing the New Filter

1. Select a filter with enough circumference to match the existing filter area and a width and fold depth as close to the original as possible. I chose a FRAM CA3681 and it was perfect. I only needed to discard about 2" and the width and depth were just right to seal inside the case.

2. Bisect the new filter into two equal semi-circles. The cuts don't need to be clean. I used wire cutters because of the screens, but heavy scissors should work.

3. Open one of the old filter casings and set aside the outer shell. Shape the new filter to match the old paper filter. It doesn't have to be exact yet. It just helps to have the shape before destroying the old filter.

Preparing the Old Filter Casing

4. First remove the paper accordian filter. I ripped it out with pliers—just try to preserve the inner screen. Don't bother removing every scrap of paper as you will probably have to chip out the old glue and paper fragments anyway.

5. Carefully pry the casing walls apart and separate the nozzle and screen from both plates. Again, try to preserve the screen as it is a handy base to attach the new filter to.

6. Clean out the old glue on both plates. This glue is old and very hard. I had to use a hammer and chisel to carefully chip it out without bending the plates too much. The plates are durable but you still need a sharp chisel.

Mounting the New Filter to the Old Casing

7. Shape the new filter around the nozzle and screen piece. Use the smaller plate (shown in the picture above) as a sizing guide and cut off any excess filter to make the ends butt up with the metal.

8. Using heavy-duty coat thread, or maybe fishing line, sew the ends of the new filter the screen on ether side of the nozzle. I had to fold the old screen a little to make room for the new filter. I considered cutting away this screen, but I decided to leave it as a guide for later filter changes.

Sealing Up the New Filter in the Casing

9. Using the silicone sealant, glue the new filter to the nozzle and the two plates. As you work, keep thinking about an air-tight seal forcing the air through the paper and plug any leaks. I ran a bead all around the rubber seal to hold it to the plates.

10. Once everything is glued up, it needs to cure for 24 hours or so. I placed heavy textbooks on it to keep it pressed tightly.

Reassemble the Filter

11. Replace the shell on the filter casing and return it to your motorcycle.