A pod filter can be a good CT90 Trail 90 solution when the factory airbox assembly is missing, broken, or incomplete. The CT90 stock airbox uses several parts, and rounding up every piece can get expensive or time-consuming. If the goal is simply to keep the CT90 motorcycle running reliably without rebuilding the entire factory intake system, a pod filter is an easy solution.
Off-road note: The factory intake system is built for deep water crossings. If you are not planning extreme water crossings, a pod filter can work fine for typical riding.
Parts and tools needed
Parts
(1) Pod filter for the CT90 carburetor inlet
Clamp included with the pod filter
Tools
Allen keys (or the correct driver for your spine cover fasteners)
Wrenches/sockets for factory air filter body bolts
Hardware note
Save and reuse the spine cover support bolt/spacer fastener if you have it. If you do not have it, plan to fabricate a support spacer (details below).
Removing the CT90 spine cover and factory airbox
Step 1: Remove the spine cover
Remove the fasteners holding the CT90 spine cover in place.
Lift the spine cover off to access the airbox area.
Note: The CT90 motorcycle shown uses Allen head bolts that were installed previously but yours might use hex head bolts.
Step 2: Unbolt the air filter body and save the reusable fastener
Locate the two bolts holding the air filter body to the frame.
Remove the front long bolt assembly and the rear bolt area where a small forked plastic feature supports the air filter body.
Set aside the long bolt assembly because it will be reused later as a support point.
Important removal detail:
The rear bolt should only be tightened enough to grab the “fork” feature. If it was tightened down too far in the past, it can be difficult to remove and may require access from the battery box side to loosen it.
Step 3: Identify common broken/missing factory airbox parts
It is common to find damage or missing parts in the CT90 airbox setup. In the video, the small tab or fork area that should be supported by the bolt is broken. This is a common break because many owners do not realize that support feature is supposed to be anchored.
If multiple parts are missing and a factory rebuild is not planned, proceed with the pod filter install.
Documenting a complete CT90 factory airbox assembly (for reference)
A complete setup typically includes:
A boot on the airbox end (rubber intake boot)
A wing nut fastener
A rear cover half with the boot
A foam filter element
An internal metal support piece
An additional spine-related plastic piece that nests into the assembly
A thin, large O-ring seal that goes around part of the airbox
Service note: If the rubber boot is rock hard, we recommend replacing it if you are rebuilding the stock airbox.
Installing the CT90 pod filter
Step 1: Position the clamp for access
Slide the clamp onto the pod filter boot.
Position the clamp so the screw faces down (bottom side). This makes access easier once everything is installed.
Step 2: Use the boot seam as a clocking reference
Identify the rubber seam on the pod filter boot.
Mark the seam with a white grease pencil so it is easy to see during installation.
Start with the seam roughly aligned to a reference on the carburetor casting (in the video, we reference the top of the carburetor body casting).
Step 3: Clock the pod inward for spine cover clearance
Push the pod filter onto the carburetor inlet.
Before tightening, rotate (“clock”) the pod inward as far as needed to ensure clearance for the spine cover.
The pod often ends up rotated to a position where it may touch the frame slightly, and the seam on the pod is offset from the seam on the carburetor by roughly about a quarter inch.
What matters most:
The correct clocking is the clocking that allows the spine cover to reinstall without forcing the spine cover to flex.
Step 4: Tighten the clamp and reinstall the spine cover
Once the pod is clocked correctly, tighten the clamp until snug.
Reinstall the spine cover to confirm it fits cleanly over the pod filter.
Verify the pod filter sits compactly under the spine cover and the cover is not being stressed.
Reinstalling the spine cover support bolt/spacer
The spine cover support bolt/spacer is important. The bolt removed earlier is reinstalled to support the spine cover at the mounting point near the pod.
Reinstall the support bolt/spacer so the spine cover has proper backing and does not flex.
Thread it in until it seats correctly.
Test-fit the spine cover and confirm the bolt hole lines up without forcing the cover.
If the support bolt/spacer is missing:
The video recommends fabricating a support using either:
All-thread and a spacer, or
A long bolt with nuts to create a support spacer
The goal is the same: provide a solid support point so the spine cover does not flex and crack.
Final checks before riding
Confirm the pod filter clamp is snug and the filter cannot rotate freely.
Confirm the pod filter is clocked so the spine cover installs without stress.
Confirm the spine cover support bolt/spacer is installed and supporting the cover.
Start the motorcycle and confirm stable idle and throttle response.
A Note on Jetting: Any change to the air filter could require a change in jetting. Unfortunately there is no exact formula to determine the jets as every motorcycle and environment will be slightly different. We recommend starting with the factory jet sizes and moving up or down based on your specific motorcycles performance.
Troubleshooting
The spine cover does not fit after installing the pod filter
Clock the pod further inward so the spine cover clears without forcing the cover to flex.
Recheck the clamp orientation and filter position before tightening.
The spine cover feels like it has to flex to line up with the bolt hole
Do not force it. Re-clock the pod and confirm the support bolt/spacer is present and correctly set.
Running the cover under stress can lead to cracking.
The support bolt/spacer is missing
Fabricate a spacer using all-thread or a long bolt and nuts so the cover is supported at the mounting point.
FAQ
Why would I run a pod filter on a CT90 if the stock airbox is better protected?
When the stock airbox is missing, broken, or incomplete and sourcing all the factory parts is not practical. A pod filter can keep the CT90 motorcycle running without rebuilding the full assembly.
Can I ride without the spine cover?
Yes. The spine cover is cosmetic. The motorcycle can be ridden without it.
How do I know the pod is clocked correctly?
The pod is clocked correctly when the spine cover installs without significant flex and the mounting hole aligns without forcing the plastic.
What goes in the empty area once the airbox is removed?
With the stock airbox removed, the area is open. Functionally, nothing is required there for the pod filter install. However, the open space becomes the perfect location for your next sticker.