640 Carb Removal Ques & Advice Sought

Discussion in 'Thumpers' started by Reformed DucFlogger, Jul 16, 2005.

  1. Reformed DucFlogger

    Reformed DucFlogger Inventor Of The Wheel Mk2

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    About to remove the carb on one of our 640s to replace the pilot fuel jet (set too lean (a 42.5) by shop, etc - see earlier posts).

    Step 1: Tank off, carb bowl drained.

    Now time for some 'plan of attack' work.

    1. Pilot fuel screw had been changed by shop, so should come out easily.
    2. Carb bowl bolts were replaced with hex bolts by shop.
    3. Have Arch's tip on pivoting the subframe down - great idea.
    4. Hoping (vainly?) I can just loosen and rotate carb to get at bowl safely, but...

    Took look at service manual - useless until carb off bike.

    The one specific question I have is the mix enrichment (a.k.a. choke) cable attachment - is it just a bolt on/bolt off affair where the cable runs into the carb at the rear opposite the TPS or is some special voodoo required?

    Looking for any and all tips/suggestions/mistakes best avoided before I get in there.

    Time to share some of that BST40 cult lore.... (praise be the BST, etc, etc, amen)
    #1
  2. RedWarrior

    RedWarrior dumbfounded dipshit

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    You don't need to remove the carb to replace the jets. You should be fine with tank and seat off. Loosen throttle cables and intake boots. rotate carb. top toward the curbside of the bike. You will now have access to the bowl bolts. When you get the bowl off, the float has a "union" of thin plastic "webbing" near the center. There is a hole above that where your pilot jet is located. Use a large mini screwdriver to remove and replace the jet and you'll be fine. Make sure you have a good small screwdriver to fit up in there or you run the risk of not tightening it enough and having the jet fall out. The bike won't run if the jet falls out. Don't ask how I know, just take my word for it. :D
    #2
  3. Reformed DucFlogger

    Reformed DucFlogger Inventor Of The Wheel Mk2

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    Excellent info - gracias.

    BTW: At the risk of hijaking my own thread - agree with you on the patriot act. Slippery slope.
    #3
  4. rjf

    rjf SBS's #1 fan in January

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    Mate I just did this on my 2003 adv. I left the choke cable in situ. just loosened clamps, disconected throtle cables, tps, fuel line, took the top off carb to get more room to rotate it. ( I was moving the needles clip position anyway ). I think that was all.

    Just make sure you pay attention to the way the float bowl and its little inlet valve go. bike won't start if its in wrong.

    I "pivoted' the subframe back to fix the above paragraph. took 2 men 10 minutes of wrestling to get it back in position 'cause its was very tight fit on the frame.

    Have you read Flannies guide, its better than the manual.
    #4
  5. potatoho

    potatoho Cheese and Rice!

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    I've got this down to a science :evil I replaced my pilot jet 5 times since yesterday. Just drain, make sure not to spill on hot motor. Drop the bowl and move it out of the way. Swap the pilot jet. Personally I only tighten my jets slightly more than I would close a bottle of soda. That brass stuff is fragile.
    #5
  6. Reformed DucFlogger

    Reformed DucFlogger Inventor Of The Wheel Mk2

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    Tatter - in situ? No carb rotation, etc? Yeah baby.
    #6
  7. potatoho

    potatoho Cheese and Rice!

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    Yes if you have allen heads already, just use some long allen wrenches and you can get to them easily. I use one of those main jet tools and a flathead bit to get the pilot out. Pilot installation with the carb vertical is more of a pain, but I first stick it in there and hold it with a finger and then use a cheap precision screwdriver to spin it in there. Then I tighten with the main jet tool.
    #7