I think I should put all of this together as a sticky so I can just post a link to it...
Carb Cleaning:
- Unscrew the cover from each carb
- Remove the airbox
- Squeeze the clamps on the fuel lines at the carb end and slide them up on the fuel line
- Remove the fuel line from the carb
- Remove the air vent lines from the carb
- Loosen the collar around the carb boot
- Remove the carb from the sled
- Loosen the jam nut for the choke plunger and remove the plunger from the carb
- Tip the carb upside down over a bowl of some sort to catch the residual fuel still inside
- Unscrew the four Philips head screws from the bottom of the bowl and carefully tip the bowl away from the body (it may feel stuck initially, moving slowly will aid in preserving the gasket)
- Squeeze the clamp on the bottom of the trap line and slide it up, remove the plug from the bottom of the trap line (you should be able to see through the trap line at this point - if not, it's plugged and should be cleaned or replaced with a new piece of fuel line)
- Check the movement of the floats on the supports - they should move easily and smoothly. You can tip the bowl upside down and right side up repeatedly to test the movement
- Stand the carb upside down on a solid surface
- Use a thin blade regular screwdriver to remove the pilot jet
- Use a wrench to remove the main jet. There is a washer under the jet and the main sleeve is what the jet is screwed into - it should slide out through the top of the carb once the jet is off.
- Using a small point nail set or similar tool, press out the pin that holds the float arm in the towers. BE CAREFUL. The towers will NOT hold up significant force, and the pin will only go one way. You may want to rest the top portion of the "far" tower on something solid (leaving a gap under the head of the pin) and lightly tap the nail set against the other end of the pin if you can't press it out by hand. Again, BE CAREFUL. If you break either of the towers, you will need to buy a new carb body. Remove the pin and the float arm - pay attention to its orientation.
- There may be a spring retaining clip holding the needle in the seat. If so, carefully remove it then tip the carb over to get the needle out
- The seat is removed using a wrench
- Remove the idle screw (knurled end with a spring over the shaft that's visible)
- Remove the air screw (slotted end, almost flush with the carb body, near the idle screw)
At this point, you can spray out the carb and all of its passages with spray carb cleaner and compressed air. Or, if things look like they're heavily gummed up / dirty, you may want to proceed to "dipping" the carbs for a more thorough cleaning.
In order to dip carbs in heavy cleaner, you need to ensure that ONLY metal parts go into the dip. This will require that you remove ALL non-metal parts as follows:
- There is a very small, plastic cap on top of each of the float guides. These pop off, but be careful to hold your hand over them while lifting so they don't fly off and disappear. Remove the floats from the guides.
- Squeeze the clamp on the top of the trap line and slide it down. Remove the line from the bowl.
- Remove any and all rubber caps anywhere on the body of the carb.
- Stand the carb upside down on a solid surface. Using a thin blade regular screwdriver, carefully lift one area of the gasket. Using the screwdriver blade as a sort of 'shim', slide it carefully around the perimeter of the bottom of the carb, separating the gasket from the body as you go.
Set aside ALL of the non-metal parts (and the small retaining spring from the needle) and place ONLY the metal parts into the carb dip. You can remove the jet needle from the slide and put that in the dip as well. I leave them in for 12 hours if very dirty. When I take them out, I drain off as much of the carb dip as I can before putting the parts into a pot of hot water (150-160 degrees). I swish everything around liberally, rinsing out as much of the remaining dip as possible (which isn't much). Then, spray everything liberally with spray carb cleaner.
Use a small gauge wire to probe through as many of the carb openings as possible as well as through all of the openings in the jets.
Putting everything back together requires that you simply reverse the process. Set the air screw to the factory setting for your particular motor. Install the carbs back into the boots on the motor and tighten the band clamps to hold them in place. Screw the choke plungers into the bodies, but don't tighten the jam nuts yet.
Check the slides to ensure that the needles are inserted correctly, the c-clips are in the proper positions, and the cables are properly seated and locked in. Insert the slides into the proper carbs (cable length will determine this) and screw the caps down fully. The slides should only go one way, but the beveled lower edge faces the inlet side.
Now, you need to sync the carbs.
- You need to adjust the free play in the throttle so that there is about 2-3mm of play. This is necessary for the safety switches to function properly.
- With the kill switch engaged and the key off, zip tie the throttle wide open (or have a buddy hold it).
- Remove the airbox so that you can easily see and access the intake side of the carbs.
- Ensure that the slide is installed correctly with the cable inserted correctly into it.
- Ensure that the slide cap is screwed on all the way.
- Ensure that the top edge of the carb slide is -just- above the bottom edge of the carb intake throat. If it is not, adjust the cable on the slide cap until it is.
- Repeat for each carb.
- Remove the zip tie / release the throttle lever.
- Rest the solid part of the drill bit in the carb opening "the long way" and adjust the idle screw until the slide -just- comes in contact with the bit. This will give you a reasonable starting point for the idle.
- Once all of the carbs have been adjusted, slowly squeeze the throttle and ensure that all of the slides begin to move at exactly the same time and go up exactly the same amount.
- Adjust the air screws according to the manufacturer's setting.
Now, adjust the choke plungers.
- Get a thin gauge piece of solid wire and bend it at a 90 degree angle about 1" from the end
- Remove the airbox so you can easily access the intake side of the carbs
- Apply the choke
- Slip the bent section of wire into the enrichment hole on one carb and release the choke - make sure that you can not easily pull the wire out
- If the wire comes out easily, you need to screw the plunger adjuster into the carb body until you feel it contacting the wire and keeping it from moving
- Screw the adjuster in another half turn from that point and tighten the jam nut
- If the wire does NOT come out easily, pull on the choke lever until you feel tension in the cable - you should only have to move the handle a small amount after you feel tension before you can remove the wire
- If, after lightly applying the choke, you still can't remove the wire, you will need to unscrew the plunger adjuster from carb body
- Unscrew it until, with the choke off, you are able to remove the wire then use the process above to adjust it correctly
- Re-install the airbox
You're now ready to start the sled and tweak the air screw and idle settings until it's where it needs to be.
While you're in there, you may want to check compression. Here's my process and follow-through:
Pull the plugs and set them aside. Make sure the sled is off and the motor is completely cold. Connect the gauge to a cylinder, hold the throttle wide open, pull (or crank the E/S) until the needle on the gauge doesn't climb any more.
Repeat for all cylinders.
Unless you know that your gauge is accurate, you might want to do a compression test on a machine that's "known good". Gauges do vary, and sometimes read too high or too low.
If you know your gauge is good, I would recommend the following courses of action:
- 120+ per cylinder: Go ride.
- 110-120, be aware that you aren't getting max performance, go ride.
- 100-110, be aware of your motor and heed any noticeable changes in sound or performance. If it's the off season, tear down the top end and freshen it up. If it's during the season, you can keep riding knowing that your performance is sub-par. Don't "push" it too hard.
- 100 or less, freshen the top end before something breaks and it ends up costing you a lot more money to repair.