Unlike many small Hondas, the CT90 / Trail 90 puts the fuel shutoff on the carburetor, not the tank so swapping fuel lines is a unique, tougher than usual job. To further complicate the setup, fuel lines run through the internal frame and back up to the tank, which means a bit more teardown than a typical motorcycle. Follow along as we break it down to the essentials of the CT90 fuel tank removal and fuel line routing for a clean, leak-free install on your own Trail 90.

Tools & Parts

8–14 mm metric sockets/wrenches
Screwdrivers
Pliers
Utility knife/box cutter
Wire brush and penetrating oil
Zip ties
Shop rags and a fuel-safe drain container
5.5mm Replacement fuel line

Safety Note

Work cold. Let the motorcycle cool before touching the exhaust or fuel system.
Ventilate. Work in a well-ventilated space away from sparks and flames.
Fuel control. The CT90 petcock is on the carburetor, not the tank so plan to drain at the carburetor.

Step-by-Step Instructions

1) Disassembly for Tank and Fuel Line Access

Remove the spine cover, air filter box assembly, and the brush/crash guard to expose the frame cavity and tank mounts.
Apply penetrating oil and brush rust off the two exhaust flange nuts at the cylinder head. Remove the two header nuts. Remove the rear muffler mount at the shock area and the lower mount hidden under the muffler (ties to a special stud on the tank). Then remove the exhaust.
Remove the seat latch/battery box cover.
Disconnect the battery: remove the fused lead and the second lead, then lift the battery out.
If fitted, remove any small accessory brackets (e.g., flasher relay mount) for clearance.

2) Lift and Secure the Fuel Tank

You don’t need to fully drain the tank to replace the fuel lines. Tilt the tank forward so fuel moves away from the outlets and secure it while you work. Use this method only if the tank is mostly empty.
Remove the four tank bolts (two per side) and lift the tank straight up.
Tie the tank up and forward so it’s supported and stable. This frees both hands and prevents accidental drops while working inside the frame.

Orientation note: The tank has two outlets (“bungs”). Right-hand outlet = reserve. Left-hand outlet = main.

3) Drain and Remove Old Fuel Lines

Because the shutoff is at the carburetor, the cleanest way to empty the fuel lines are to disconnect at the carburetor and drain into a safe container before removing.
If old hose is hardened, carefully slit the hose lengthwise at the barb with a utility knife and peel it off with pliers to avoid twisting the carburetor or fuel tank fittings.

4) Install and Route New Fuel Lines

Cut two lengths of new fuel line. We like to leave these slightly longer so there is extra to trim when needed down the road.
Lightly lube the fuel line barbs on the carburetor (a tiny drop of marvel mystery oil helps tough fuel line seat fully).
Push each line fully onto its barb until seated.
We like to add a red zip tie loosely to the reserve line and a green zip tie to the main line to remember which line goes where during routing and future service. Any sort of indicator will work.
Route the fuel lines through the frame, into and through the main cavity and back out where they exit for each tank barb.
Trim ends cleanly and push onto the tank bungs: left bung = main, right bung = reserve. Using a drop of oil for lubrication, push the lines onto the fuel tank barbs until fully seated.
Untie the gas tank and pull the small amount of slack into the frame cavity so the tank can tilt up during future service without disconnecting lines.
Avoid leaving a large loop stuffed inside the battery compartment. Aim for smooth, gentle arcs.
If you are installing the 5.5mm fuel line with additional fuel line clamps, install those now.

5) Reinstall Tank and Hardware

Reinstall the four tank bolts.
Refit battery box components and the battery (ensure the fused lead is connected).
Reinstall the air box, spine cover, and brush/crash guard.
Reinstall the muffler in with the header flange nuts last. This is a good time to replace the exhaust crush gasket if sealing is poor. We like to apply anti-seize on the cylinder head studs to make removal easy in the future. Do not over-torque.