78 Yamaha DT 400B start up

Discussion in '2 smokers' started by Imflyinn, Jun 1, 2013.

  1. joexr

    joexr Banned

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    You mean the top where the cable is?
    #21
  2. Imflyinn

    Imflyinn Adventurer

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    Yes. It would probably come off if I forced it but did not want to take any chances
    #22
  3. joexr

    joexr Banned

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    Be very careful , the cast aluminun is brittle. Will the slide inside move up and down?
    #23
  4. Imflyinn

    Imflyinn Adventurer

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    The slide is stuck closed and will not move at all
    #24
  5. joexr

    joexr Banned

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    If the slide is stuck , top is probably stuck worse. You could try a big pair of channellocks on the top , but you just don't want to squeeze it. Can push the slide up with your thumbs or twisting a big screwdriver under it?
    #25
  6. Imflyinn

    Imflyinn Adventurer

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    I tried pushing it decently hard with a screwdriver, it's stuck really good and won't move at all
    #26
  7. joexr

    joexr Banned

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    It's all aluminum. I don't know what might soak it loose. Somebody else may have ideas tommorrow or maybe ask about it at a car or bike shop. I'll try to get back tommorrow. :thumb
    #27
  8. Imflyinn

    Imflyinn Adventurer

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    I looked online and came up with a bunch of things to do, but they are all different. I can't get to the bike until tomorrow night so I'll let it soak until then and see what happens, hopefully it will be at least a little better!
    #28
  9. joexr

    joexr Banned

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    If you go to page 55 , post 816 of the 2-stroke picture thread , there's a pic of your bike.
    #29
  10. motrhead

    motrhead Travellin' Soul

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    I recently bought two 400 2 stroke Yamahas: I wanted the 78 IT400, and it came with a 78 DT400MX , which according to the list here is a DT400e:
    http://www.merrittmotorcyclesalvage.com/yamahaidentification.htm

    I used spray carb cleaner to free up the stuck slide/piston in my IT carb. I kept spraying frequently (from top and bottom) to keep it wet for a while and to make sure it had time to soak thoroughly, and then carefully, and not *too* forcefully, put a flat blade screwdriver in each side and pried straight up with equal force on each side. If you do this be careful! You can mess up the piston quite easily. I really should have soaked the body in carb cleaner, but there was not a lot of obvious varnish in my carb, and it freed up quite quickly, but it did take a bit of force.
    After cleaning out the sludge in the tank, lines and petcock, changing transmission oil and investing in a new iridium plug, it started third kick. I just swapped out the old fork oil for new 15 weight Belray, and I still have to invest in a new agressive knobbie, cause this thing just spins the tire through 4th gear. When it does hook up, I just hope I am pointed in the right direction 'cause I get there in a hurry, and it doesn't have a lot of brakes! LOL. I am having a blast on the IT, and hope to get started on resurrecting the DT soon.
    #30
  11. anonny

    anonny What could go wrong?

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    Last time I had a seized carb slide I used a high quality penetrating oil and soaked it for a few days, then I pried ever so gently with a piece of plastic and it broke free with little force.

    A few heat / cool cycles from a blow dryer may help.

    I'd do a leak down test or change out the crank seals before firing it up.
    #31
  12. Imflyinn

    Imflyinn Adventurer

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    Its awesome seeing all those Yamaha enduros together on the picture page! I didn't get a chance to try the carb tonight, hopefully I will tomorrow. Anyone know if the slide and sleeve are the same metal? There looks to be very little if any gunk around the carb. And what about freezing the carb? Everything I have seen has said to use heat, but could getting it cold make the sleeve expand and free it up?
    #32
  13. joexr

    joexr Banned

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    Might be worth a try , couldn't hurt. How are you going to get it off of the cable?
    #33
  14. Imflyinn

    Imflyinn Adventurer

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    Got it unstuck and pulled all apart! Lots of WD-40 and then hit it with a screwdriver and it slid right out, and there is no rust there was only some varnish holding it
    #34
  15. joexr

    joexr Banned

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    Cool.:clap Hope the rest goes as well.
    #35
  16. gloud

    gloud Been here awhile

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    For varnish a little heat (heatgun) will help. Good luck
    #36
  17. Imflyinn

    Imflyinn Adventurer

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    I got the case pried open today and there is more varnish inside the case that needs to be cleaned out. I keep reading to soak the carb in carb cleaner, by soak should I fill a bucket with cleaner and let the carb sit in it for a while or keep spraying and drying it?
    #37
  18. Imflyinn

    Imflyinn Adventurer

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    Also the air filter is crumbling, it is like a triangle shape is it safe to use or should I try and find a new one?
    #38
  19. joexr

    joexr Banned

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    Try to find a filter. You don't want to suck dirt or crumbling filter thru the motor. The carb isn't really that complex. I'd just take it apart and shoot carb cleaner all over it and thru all of the passages.
    #39
  20. Imflyinn

    Imflyinn Adventurer

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    Is carb cleaner what I should be using or would there maybe be something better for it?
    #40