The effects of time can take a toll on a motorcycle, especially if it has been stored without regular maintenance. While there are many 1982 Yamaha Maxim 650s on the road still, many more are squirreled away in a dark corner of a garage or shed. Fuel contamination, and the resulting clogs within the carburetors, are one of the more common problems that a Maxim owner will encounter while preparing the motorcycle to be ridden again. A thorough cleaning will remove any debris and clogs from the carburetors' passages, but the process will take some patience to complete.
Things You'll Need
- Ignition key
- 10 mm socket
- Socket wrench
- Phillips screwdriver
- 10 mm wrench
- Flat screwdriver
- Carburetor cleaning solution
- Compressed air
- Float chamber gaskets
Unlock the seat latch on the right side of your Maxim with the ignition key, then lift the seat off of the motorcycle's frame rails. Pull the left and right side covers, positioned below the seat, off of the motorcycle's frame.
Unscrew the single bolt at the base of the gas tank with a 10 mm socket and a socket wrench. Set the fuel valve on the left side of the tank to the "Off" position, then pull the vacuum line and fuel hose off of the valve. Grasp the base of the tank and lift it up slightly, then pull the tank toward the rear fender until you can remove it completely.
Loosen the bolt at the top of the air box, positioned between the frame's seat rails and the battery box, using a 10 mm socket and a socket wrench. Loosen the clamps attaching the air box's flanges to the carburetors with a Phillips screwdriver. Pull the air box and its flanges away from the carburetors.
Loosen the clamps attaching the carburetors to the motor's intake flanges with a Phillips screwdriver. Pull the carburetors off of the motor as an entire assembly, then out through the left side of the motorcycle's frame.
Loosen the throttle cable's lock nut on the top of the carburetor assembly with a 10 mm wrench, then pull the cable off of the carburetors' throttle valve. Pull the choke cable off of the lever between the carburetors on the right side of the assembly.
Reinstall the carburetors onto your Maxim after they have been cleaned, following the reverse method of removal.
Disassembling and Cleaning the Carburetors
Unscrew the brass drain screws, positioned on the bottom of the carburetors' float chambers, with a flat screwdriver. Set the drain screws in a separate pile. Empty any remaining fuel in the float chambers into a container. Unscrew the bolts attaching the float chambers to the bottom of the carburetors with a Phillips screwdriver, then pull the chambers and their gaskets away from the carburetors.
Flip the carburetors upside down. Push the pivot shafts out from the carburetors' floats with a small pick, then remove the floats from the carburetors. Pull the float valves out from beneath the floats' mounting points, then unscrew the valves' seats with a 10 mm socket and a socket wrench. Unscrew the main and pilot jets, positioned just off center from the bottom of the carburetors, with a flat screwdriver. Place the jets, float valves, float seat, float pivot shafts and the floats into separate piles.
Flip the carburetors right side up. Unscrew the bolts from the carburetors' top caps, then lift the caps away. Pull the diaphragms with their jet needles and springs out of the top of the carburetors by hand. Push the needles up and out of the diaphragms.
Remove the carburetors from their brackets, using a Phillips screwdriver. Pull the carburetors apart from each other and remove the plastic tubing running between each carburetor.
Soak the jets, float valves, float seats, needles, drain screws and the disassembled carburetor bodies in a container of carburetor cleaning solution for at least two hours.
Remove the carburetors and their parts from the cleaning solution and dry the parts with compressed air. Blow compressed air through the passages cut into the carburetor bodies and through the jets and valve seats to clear any remaining clogs or debris.
Reassemble the carburetors, following the reverse method of disassembly. Install new float chamber gaskets if the original gaskets are brittle or torn.
- "The Professional Motorcycle Repair Program"; Professional Career Development Institute; 1995
- Yamaha XJ650J Service Manual"; Yamaha Motor Corp.; 1982
- "Yamaha XS650 & 750 Fours Owner's Workshop Manual: 1980 - 1984"; Pete Shoemark; 1999
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