My Yamaha Blaster Won't Start: Carburetor

Remove the seat by unscrewing the bolts found on the four corners of the seat. Remove the clamps from the top of the air box using a pair of pliers to access and remove the air filter. The air filter is removed by unscrewing the wing nut and sliding the filter out of the box. Loosen the hose clamp that connects the carburetor to the intake manifold, using a screwdriver.

Loosen the fuel delivery hose clamp with a screwdriver and pull the carburetor out of the Blaster. Before troubleshooting the carburetor, it's important to note whether you've made a significant change in altitude or a change in your exhaust/intake setup. If you've made an altitude change, installed an aftermarket exhaust pipe or modified your air box, the jets will need to be changed. Refer to your manual for specific re-jetting instructions based on your altitude. Your exhaust kit will provide a recommended jetting setup. Do-it-yourself modifications like removing an air box will require you to experiment with the jet setup until you find the right one.

Disassemble the carburetor by unscrewing the bowl screws from the bottom of the carburetor. With the bowl removed, the float, pilot jet and main jet will be exposed. To remove the pilot and main jet, unscrew them from their respective holes. The main jet will sit in the exact center of the bowl, while the smaller pilot jet will be set just below the main jet.

Use a blunt object like a stick or rod to push the bottom of the needle receiver assembly out of the carburetor. The needle receiver (which houses the needle jet) will slide out of the top of the carburetor along with the slide, spring, carburetor cap and gasket. The carburetor is now completely disassembled and ready to be inspected.

Inspect the pilot jet for blockage, slide a thin wire through the pilot jet's hole, spray it with carburetor spray and blow the center hole with compressed air. Repeat this process with the main jet. If there is any blockage or wear, replace the jets. If you have made altitude changes or exhaust/intake modifications, insert jets that correspond to your changes as recommended in your manual. Note that this may take some experimentation with different jets to get the correct jet setup, as there are many jet sizes for different scenarios.

Inspect the bowl, floats and ports for any signs of debris or gunk. If debris or gunk is found, remove it using a spray carburetor cleaner, soft wire brush, or thin wire (to insert into small orifices). If no gunk or debris is found, you've ruled this out as a possible cause for the starting issues, and can focus on the replacement of carburetor components.

Look for abnormal wearing on the jets, float valve, gaskets, O-rings and springs. If you have not changed altitude or modified your bike in any way, then it is best to inspect these components. Any one of these components, or a combination, may be contributing to your starting issues. You may choose to replace individual parts such as a new float valve, though replacing all the interior components with a carburetor "rebuild kit" is advised. Rebuild kits can be ordered online or through your dealer, and will ensure your carburetor is fully repaired.

Slide the gasket, spring, spring holder and needle jet assembly back onto the carburetor cap and insert the assembly into the top of the carburetor. Screw the main jet into the bottom of the needle jet assembly by accessing it through the bowl area. Screw the pilot jet back into its hole below the main jet. Clip the float valve onto its hinge within the bowl a insert the bowl gasket. Screw the bowl to the bottom of the carburetor to complete the re-assembly process.

Re-attach the carburetor to the intake manifold using the hose clamp and screwdriver. Slide the fuel feeder line onto the brass receiver port on the side of the carburetor and slide the air box boot over the carburetor's intake port, which should be facing toward the back of the bike. Re-install the air filter with its wing nut, slide the clips over the air box top to secure it to the box and slide the seat into place. Re-install the seat screws to complete the re-assembly process.

Prime the carburetor by twisting the throttle once and start the Blaster.