SAFETY FIRST: Protective gloves and eyewear are recommended at this point.
Carburetor Disassembly
Remove the carburetor. See the Carburetor Removal topic for more information.
Remove the four Phillips head screws that secure the carburetor float bowl in place using a #2 Phillips head screwdriver. Remove the carburetor float bowl and check the O-ring for tears or other damage. Replace as necessary.
Use a pick or suitable tool and remove the float pin from the carburetor.
Remove the float and the attached fuel valve.
Remove the four Phillips head screws that secure the carburetor top in place using a #2 Phillips head screwdriver.
Remove the carburetor cap along with the spring.
Remove the diaphragm/slide assembly.
Carburetor Inspection
Inspect all fuel lines for dry rot or cracks. Pay particular attention to any hoses that have been pinched. Damaged fuel hoses and vacuum lines and vent hoses should be replaced as needed.
Inspect the fuel valve, if the Viton (rubber) tip is worn replace it. Push in the plunger on the other end of the fuel valve and make sure the spring inside pushes the plunger back out. Inspect the brass fuel valve seat for debris or damage. Clean with aerosol carburetor cleaner and a Q-tip.
Use a small flat blade screw driver and remove the pilot jet. Hold the pilot jet up to the light, you should be able to see through it. If the jet is clogged use aerosol carburetor cleaner and/or compressed air to remove the debris.
Use a flat blade screwdriver and remove the main jet from the main jet holder. Hold the main jet up to the light, you should be able to see through it. If the jet is clogged use aerosol carburetor cleaner and/or compressed air to remove the debris.
Remove the main jet holder using an 8 mm wrench. Check to make sure all of the small holes are clear, use aerosol carburetor cleaner and/or compressed air to clean them out.
Inspect the diaphragm for tears or damage to the slide-replace as needed.
Insert the tang on the float through the tiny wire clip on the fuel valve.
Place the fuel valve into the fuel valve seat and slide the float pin in place.
Check the float height using a float height gauge as shown. If the float height is not within specification, bend the float tang until you achieve the correct float height.
Float height: 15.5 mm to 19.5 mm
Carburetor Reassembly
Install the main jet holder and snug it down. Be careful not to over tighten it, as the threads are very fine and easily stripped.
Install the main jet, again making sure not to over tighten it.
Install the pilot jet.
Replace the float bowl and tighten the four screws securely.
If the engine has been modified and is running lean in the mid-range, a 3 mm ID washer can be placed on the needle under the head to raise the needle and richen the mid-range, but this is in violation of some emissions regulations and should only be done where legal. The fine for tampering with emissions control devices can be pretty hefty, so use your best judgement.
Reinstall the slide and diaphragm assembly, making sure that the slide needle fit into the main jet holder and that the slide moves freely. Reinstall the spring and diaphragm cover, making sure the rubber diaphragm is seated in the groove of the carburetor completely. Tighten the four screws securely.
Install the carburetor. See the Carburetor Installation topic for more information.
Use a thread locking agent on the throttle cable holder screw such as Loctite red.
Use a 10 mm wrench and adjust the throttle free play at the carburetor.
Remove or add free play as needed using the adjusters at the top of the cables.
Throttle free play: 2 to 3 mm
Start the engine and make sure the idle doesn’t change when turning the handlebars from left to right, if this happens you will need to re-route the cables and re-check the throttle free play.
To adjust the idle speed turn the idle speed knob in to raise the idle or out to lower the idle. Only turn the screw slightly when making an adjustment.
Carburetor idle speed: 1,200 to 1,400 rpm