How to Clean & Rebuild Yamaha 90HP Outboard Carburetors

Need help cleaning and rebuilding the carburetor on a Yamaha 90HP outboard? All the necessary steps to clean and rebuild the carburetor(s) on a Yamaha 90HP outboard motor are listed below. 

Watch the video above and follow the steps below to learn how to clean and rebuld the carburetors on a Yamaha B90TLRX outboard.

Tools and Parts - Yamaha B90TLRX Carb Cleaning & Rebuild

• Ratchet and extensions
• 10mm swivel socket
• 10mm thin wall socket
• Assorted screwdrivers
• Dead-blow hammer
• Pliers

• Pick tools
• Impact driver 
• Contact/brake cleaner
• Carburetor repair kit
• Carburetor cleaner

NOTE: The Yamaha B90TLRX has three carburetors, so you'll have to get three repair kits. You can purchase OEM Yamaha carburetor parts individually, but it's cheaper to get the complete Yamaha carburetor repair kit that includes everything you need for this job. 

Removing the Carbs From a Yamaha B90TLRX Outboard

Step 1. Unfasten the two latches and remove the top cowling.

Step 2. Remove the four screws holding the silencer cover, followed by the cover itself.

Step 3. Remove the two bolts holding the bracket to the front of the oil tank.

NOTE: There's a ground wire attached to the lower of the two bolts, which you'll need to remember to reattach when you reinstall the bolts.

Step 4. Remove the carburetor throttle linkage from the right side of the carburetor assembly. The linkage is held in place by three pop-pins, and can be removed by pulling it off the carbs.

Step 5. Remove the six bolts from the bracket that hold the carburetors to the intake manifold.

Step 6. Disconnect the vacuum hose located on the right side of the powerhead; the fuel hose on the left side of the powerhead; the vacuum hose on the underside of the carburetor assembly; and the oil linkage from the left side of the bottom carburetor. 

Watch the clip below to see how to perform this step. 

Step 7. Disconnect the fuel enrichment assembly's blue wire from the right side of the engine, and the black ground wire bolted to the lower left side of the engine block.

PRO TIP: Use a ratchet, extension and a 10mm swivel socket to access the ground wire bolt.

Watch the clip below to see how to perform this step.

Step 8. Remove the carburetor assembly from the outboard. 

NOTE: The three carburetors are not identical. The bottom carburetor has an input for the oil delivery system; the center carburetor has the fuel enrichment starter assembly; and the top carburetor has neither.

Step 9. Remove the remaining fuel hose assembly that connects the three carburetors.

PRO TIP: Be careful when removing the fuel hose assembly, as the various hoses become brittle over time. If you damage a hose or any are already split or torn, replace them.

NOTE: In the next section, we work on a single carburetor at a time.

Cleaning & Dismantling the Carbs From a Yamaha B90TLRX Outboard

Step 1. Thoroughly clean the carburetor with contact/brake cleaner. 

PRO TIP: Removing as much dirt and debris as possible minimizes the chances of debris entering the carburetors when they're disassembled.

Step 2. Remove the four float chamber cover screws and the cover itself from the underside of the carburetor.

PRO TIP: If the four screws are difficult to loosen, place a screwdriver over each and hit the screwdriver with a hammer to "shock" the screw threads and break them loose. If that doesn't work, use an impact driver to break the screws loose.

Step 3. Remove the old float chamber gasket.

Step 4. Remove the screw holding the float arm pin, followed by the float itself.

Step 5. Use a pick tool to remove the float needle valve and its clip from the float.

Step 6. Inspect the float for signs of wear or damage, and replace it if necessary.

Step 7. Remove the needle valve seat from the carburetor using a 10mm thin wall socket. 

NOTE: There's an O-ring on the end of the needle valve seat.

Step 8. Remove the rubber pilot jet cap, and unscrew the pilot jet from the carburetor.

Step 9. Unscrew the metal main jet cap and the main jet itself from the carburetor.

PRO TIP: The pilot jet and the main jet in older carburetors can often seize in place. To free them, apply penetrating oil and let it sit for a few minutes before unscrewing the jets.

Step 10. Thoroughly clean the pilot jet and the main jet by squirting carb cleaner through them. Make sure the jets are completely clean and there's no dirt or debris blocking them.

Step 11. Squirt carb cleaner though the pilot jet, main jet and float needle valve channels within the carburetor body to remove any dirt particles from them.

Step 12. Blow every channel and hole in the carburetor body with compressed air to ensure they're completely clean.

Step 13. Remove the pilot screw and inspect it for pitting or wear, and replace it if necessary.

Rebuilding the Carburetors on a Yamaha B90TLRX Outboard

Step 1. Reinstall the pilot screw and tighten it until it bottoms out, then back it off by one and a quarter turns.

Step 2. Reinstall the pilot jet into the carb, and install a new rubber cap (included in the Yamaha carburetor repair kit) over the pilot jet.

Step 3. Reinstall the main jet into the carb with the end with the hole through it facing outward, then reinstall the metal cap.

PRO TIP: Don't overtighten the pilot or main jets, because they're made of brass and can easily be damaged.

Step 4. Install the new O-ring over the new float needle valve seat (both included in the carburetor repair kit), then install the new O-ring/valve seat into the carb.

Step 5. Install the new clip (included in the carburetor repair kit) into the float.

Step 6. Attach the new float needle valve (included in the carburetor repair kit) to the clip in the float.

Step 7. Reinstall the float into the carburetor so the float needle valve slides into the float needle seat, then reinstall the screw that holds the float arm pin.

Step 8. Install the new float chamber gasket (included in the carburetor repair kit) onto the float chamber.

Step 9. Reinstall the float chamber onto the carburetor, followed by the four screws.

Step 10. Repeat the cleaning, dismantling and rebuilding processes for the other two carburetors.

Step 11. Reinstall the fuel hose assembly that connects the three carburetors. 

NOTE: Replace any sections of hose that are worn, split or torn.

Reinstalling Yamaha B90TLRX Outboard Carbs

Step 1. Reinstall the six bolts into the carb bracket, and lay the bracket down with the bolts pointing upward. Next, thread the carburetor assembly down over the bolts.

Step 2. Lift the carburetor assembly/bracket and reinstall it over the intake manifold. Tighten the upper bolts first so they'll support the weight of the assembly.

Step 3. Reattach the vacuum lines, electrical cables, the fuel line and the oil linkage. 

Watch the clip below to see how to perform this step.

Step 4. Reinstall the carburetor throttle linkage to the right side of the carburetor by pressing it back into place.

Step 5. Reinstall the two bolts holding the bracket to the front of the oil tank (don't forget the ground wire attached to the lower bolt).

Step 6. Reinstall the silencer cover, reattach the top cowling and you're done.