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78 xs 400 E rebuild and modify

Discussion in 'The Garage' started by Tyler Shiells, Mar 30, 2017.

  1. BBS360

    BBS360 XS400 Guru Top Contributor

    The mark is under the contact breaker Cam which is bolted to the camshaft, visible in the last photo.
     
  2. Ah I figured once I looked a little better that the contact breaker can be removed. Thanks for your help.
     
  3. I'm gonna assume the gaskets on the choke plunger are crucial? One of them is cracking and rock hard and not even sealed against the nut.

    Actually I don't even have the choke knob.
    Is there any spring that needs to be in there?
     
  4. xschris

    xschris a lifestyle not a trend Top Contributor

    You have bs/34 carbs.
     
  5. Thanks.

    It appears mikes xs650 direct has them. It's listed for 80-84 xs650 bs34. Am I correct to assume that is referring to the same carbs I have?
    Also are they just dust seals? When they're shot do they effect the carbs performance?
     
  6. xschris

    xschris a lifestyle not a trend Top Contributor

    No, those will work only with 80-82 sohc xs400 carbs. The 77-79 xs400 carbs have a smaller choke plunger/rod and boot. You would have to get one for those years. I would get the oem part number and google the part.

    DSC03237.JPG 77-79 on right and 80-82 on left.
     
  7. Thanks for the clarification.

    All these little parts that need replacing are really adding up. Guess it's to be expected with a bike in the condition that I got it.

    Sure is a shame that people leave these old bikes outside,in the extreme weather we get up in canada, just to rot away.
     
  8. So I put the engine back in the frame this wknd. No exhaust or carbs hooked up. Filled it with oil and there is literally ZERO compression.
    When the engine was out and I turned it over with a wrench it felt like compression was building.
    But the kicker is so easy to move, even with my hand.
    Any ideas where I went wrong?
     
  9. BBS360

    BBS360 XS400 Guru Top Contributor

    Valves?
    Clearances set?
     
  10. Valves clearance are in spec.

    I took the left cover off and turned it over with my finger on the plug hole and I feel compression. But the kicker isn't creating compression.
     
  11. xschris

    xschris a lifestyle not a trend Top Contributor

    Clutch maybe for the kicker. Did you disassemble it at any time? I see you did. There are two arrows that need to line up with the basket and pressure plate. If you don't it will not work.
     
    Last edited: May 22, 2017
  12. That's prbly it.
    I thought of that before I put oil in but said nah I think I aligned them. In hindsight I should have double checked.
    Going to check right now.
     
  13. Turns out they were aligned. And the kicker still won't crank it.

    I'm stumped what it could be. I only took the top end apart aside from the clutch. And like I said I can turn it over with a wrench to create compression.
    The kicker does move the clutch aroun. I'm assuming it should be moving the rotor as well? I set the rotor on LT and it's not moving when I push the kicker down.
     
  14. I did have the worm gear out from the clutch cable. I cleaned it and greased it. The nut and screw are completely seized in there so I can't adjust it. Maybe I installed the worm gear incorrectly? The clutch handle is quite tough to pull.
     
  15. xschris

    xschris a lifestyle not a trend Top Contributor

    You need to be able the adjust the worm. If not you will have these issues.
     
  16. So pulled the worm and put in a vice that I padded with some cloth towels. I used a alot of PB and managed to get the lock nut of with only minimal warping of the soft housing. Put it back in and adjusted and it kicks over and gets compression.
    Always a great feeling to get a seized nut loose.
    Also one of the stud bolts on the manifold broke. So I filed the sides flat and gripped it with vice grip pliers. Alot of PB and about and hour later with several times resetting the pliers it finally backed out.
    So successful day of just removing jammed up bolts.
    This bike is becoming quite the bear to work with.
     
  17. So after replacing the header bolt and fixing the exhaust back on.
    Got some hose clamps and attached the carbs.
    Stuffed some uni foam in the intake boots.
    Jerry rigged a battery with a bungee
    Made a "gas tank" with a funnel and hose.
    20170529_175438.jpg
    20170529_175426.jpg
    The damn bike actually fired up and idled and revved. Just long enough to empty the bowls. It idled rough but that's to be expected.

    So happy it's a runner!!

    Now I can actually order some parts to get it running right and actually road worthy.
     


  18. A video of it idling.
    Surprisingly it idles alright with no tuning yet. I did set the timing and bench sync the carbs.
    I'll be order some uni pods and a few jets then sync em with a homemade manometer.

    Still need to build a seat. The one I have it pretty done and rusted out all the bolts.

    I have taken all the calipers and master cylinders apart. They all need a full rebuild.
    I'll try to salvage the rear master cylinder as there is only one place i can find that seems to sell a replacement.
     

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