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82' 750 Resurrection

Discussion in 'XJ Technical Chat' started by Brandon Spencer, Oct 8, 2019.

  1. Brandon Spencer

    Brandon Spencer Member

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    Hello everyone,

    New member here and I recently acquired a 82' 750 Seca. 13K original miles.

    This bike is going to need a ton of work and electrical is my main concern right now.

    Currently the start button does not work, I believe the starting solenoid (it clicks, but no dice) needs to be replaced. Or there is a mess with all of the safety checks this bike has.

    Jumping to the starter and supplying power to bike does result in turnover and spark! Kill switch is functional. Interesting that the tac needle goes all the way over when rocking the kill switch (in pics)

    No lights work and if you noticed I do not even have the main headlight...just the aux. Wiring in the front is a total mess and there are tons of cut and spliced wires.

    My main question to the group is where/how should I start? I've reviewed the electrical diagrams that others have posted and I believe I can follow it. I'd like to get the bike to turn over with it's current controls and see if she will run once carbs are cleaned and I get a stock airbox in. Previous owner put pods on and did not re-jet, so I cannot see it running properly.

    I do plan on tearing down this bike entirely, but would like to feel better about the electrical. Future may be stripping down to bare minimum and removing the Atari entirely.

    Looking for all suggestions and assistance to bring this bike back.
     

    Attached Files:

  2. Polock

    Polock Well-Known Member

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    solenoid is a good place to start (ha ha ha) your going to use it a lot. a new battery and little charger is next. use just the charger while you get the wires sorted out, the sparks won't be as big as the battery would make.
    it should start and sort of idle without a airbox. once you get that far, it's all down hill
     
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  3. Brandon Spencer

    Brandon Spencer Member

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    Followed wires from the ignition switch and found one disconnected. Twisted that pair back together and tried to start her up via the button and all good! I will need to take the switch apart however since the connection is intermittent.

    Seems my original thought of the starter solenoid was incorrect.

    Yes, a new battery is on it's way and using a jump pack for power currently. Now that she turns over with the switch I feel a little better being able to sort out the other connections...

    I already have the carbs apart and they need a deep clean. Intake boots also need to be replaced as all are dry rotted. I plan on trying to get her to fire up once carbs are cleaned just to make sure everything sounds good.

    Excited for this project and appreciate all the input!
     
  4. Jeromey Green

    Jeromey Green New Member

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    I just got an '82 750 maxim from a friend, she's in surprisingly good shape except for a few weird little "fixes" from the PO and the expected age related issues. I'll watch for posts from you about your build!
     
  5. Colin 85 700

    Colin 85 700 Active Member

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    Check out k-moe and the "church of clean" for yr carbs.
    Other than that these bikes are relativley easy to work on andfix have fun!
     
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  6. Sean Howe

    Sean Howe New Member

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    I am doing the same thing on a 1981. I've had some of the same problems, although, my starter selenoid was missing. My main head light didn't work until I eventually got it running. I am still having carburetor issues. Good luck! someone with mediocre mechanical skills had been working on mine also. That makes it more of an "adventure".
     
  7. XJ550H

    XJ550H Well-Known Member Premium Member

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    if your bike is an 81 seca 750 it has a headlight relay and headlight comes on when bike starts.
    start your own thread so you have history on your repairs
     
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  8. XJ550H

    XJ550H Well-Known Member Premium Member

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    starting your own thread will help you and us a lot
     
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  9. Brandon Spencer

    Brandon Spencer Member

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    Well starting to tear carbs apart was fun...seems the PO broke one of the air/fuel screws...

    Was able to drill it out (thankfully) and also confirmed threads are OK.

    Carbs are beginning their "Church of Clean" journey by soaking in ultrasonic cleaner.

    Also performed some initial compression testing:

    Cyl 1: 115
    Cyl 2: 130
    Cyl 3: 130
    Cyl 4: 100

    A little worried about 4 but this bike will be getting a full tear down in the future. So if it doesn't work initially, it'll get fixed.

    If you guys have any recommendations to a full carb rebuild kit, I'm all ears. Most of the jets are torn up and well the one air/fuel screw is no more.

    Slides look good and the rubber diaphragms will clean up just fine


    20191029_180036.jpg 20191029_184750.jpg
     
  10. XJ550H

    XJ550H Well-Known Member Premium Member

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    look in the catalog or send an emal to www.xj4ever.com fot your carb parts
     
  11. Polock

    Polock Well-Known Member

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    i don't think that one's saveable :)
     
  12. Brandon Spencer

    Brandon Spencer Member

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    Thanks!

    Next update will be once carbs are rebuilt and hopefully she starts!
     
  13. XJ550H

    XJ550H Well-Known Member Premium Member

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    a little jb weld and its fixed:confused:
     
  14. Brandon Spencer

    Brandon Spencer Member

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    Pic Heavy update!!

    So I have been busy working on the XJ, cleaning and waiting on parts.

    Took the carbs though the "Church of Clean" and really happy how they turned out. Brackets, bolts etc. were wire wheeled to be cleaned of rust and replaced if needed.

    I will comment just before each photo for details on my process.


    Initial state of the carbs:
    20191007_124607.jpg



    Before and after pic of ultrasonic soak. Part simple green ultra and water. 50C for 45 min
    20191029_203839.jpg


    State of the carb bowls before undergoing cleaning
    20191030_134916.jpg

    Every single carb bowl drain screw was rusted and seized. Heat and a Dremel allowed me to get all of them out.
    20191030_165527.jpg

    All air jets were cleaned with carb cleaner and small wire wheel
    20191108_191352.jpg

    Installed new needle and seat. New main and pilot fuel jets, stock jetting. Carb floats checked and set to proper height
    20191112_132803.jpg

    Carb rack fully assembled and performed a quick bench sync.
    20191112_154651.jpg

    Drained the bike of oil and changed filter. Had to re-shape the filter bolt until my new one arrives. No metal shavings found!
    20191113_190059.jpg

    I performed a fuel leak test, no issues. Checked all bowls for fuel. Mounted back onto bike and added new fuel line with filter (will change in future)
    20191113_201111.jpg


    At this point I attempted to start the bike. Got one little cough and then nothing after, even with some starting fluid. I knew I had a weak spark to begin with and decided to look further into the plugs.

    Seems the PO installed the wrong plugs (Autolite 403), so I picked up NGK BP7ES plugs today to hopefully solve this.

    Bike fired up with a little help with starting fluid but could not stay running on it's own fuel. Again I suspected the weak spark, even though the spark was better than the other plugs, it was noticeably small.

    20191114_134049.jpg


    So to conclude my testing for tonight, I went to the ignition coils....

    Each primary coil gave an ohm reading of 3, which is over the 10% variance stated by the manual. There was my first clue...

    Each secondary coil showed a open line, even removing the boots and going right to the wire I got nothing. Soooooo there's my problem.

    Time to order some new coils and try this again. My guess is there's enough spark to ignite starting fluid, but when fuel takes over it's not enough
     
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  15. Brandon Spencer

    Brandon Spencer Member

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    After reading some other posts on Ignition coils, I went back and measured mine again.

    Primary coils are showing between 2.7 and 2.8 ohms. Reasonably within spec.

    Fully removed all boots to get better reading on secondary coils and got 11 to 11.2 on each coil. Measuring with boots on shot up to 20.

    So before I pull the trigger on new ignition coils, sounds like some wire trim and new boots would help....
     
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  16. Timbox

    Timbox Well-Known Member

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    Very nice post update! Keep them coming
     
  17. XJ550H

    XJ550H Well-Known Member Premium Member

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    have you adjusted the idle to keep bike running?
    did you do a wet set on the floats to get them in spec a dry set of float height is a guesstiment of level just a starting point on the carbs?

    that paper filter may also be an issue
     
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  18. Timbox

    Timbox Well-Known Member

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    Are you running the bike from the stock gas tank? That tank is all clean and no rust in it? Those paper filters are not the best for the motorcycle applications. I have one on my old IH tractor and it works fine. These bikes will need a little better filter most of use use the copper cone type or one of the cartage types that unscrew and you can replace the filters.

    As stated above, take the time to bench test your carbs and check the fuel height in each bowl with a transparent tube. Only do this is you want to make sure the bike will run at it's peak performance and not starve the bike on wide open throttle. Bench testing the carbs off the bike will also make sure that all the "O" rings are not leaking and that the bowl gaskets are not leaking.
     
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  19. Brandon Spencer

    Brandon Spencer Member

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    She runs!!!

    I changed the spark plug boots and got better readings than before. I also opened the mixture screw a half turn more before trying to start.

    Choke on and she fired right up! Idle is high as I think my bench sync was not done correctly. I turned down each sync screw a little bit, but I also believe that cylinder 2 isn't firing all the time. Checked the headers with temp gun periodically.

    There is still work to be done but confirmed life!

    I am not using the stock gas tank, made a external tank hanging from ceiling. Fuel flow is good and I will def be changing out the filter for final assembly as it's too big anyway.

    My next steps include running the bike some more while adjusting the idle screws and re-check compression.
     
  20. Timbox

    Timbox Well-Known Member

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    Nice well done! You can move the idle screw a bit but don't play around with the sync screws unless you have a sync gauge set up. You can do it by listening to the idle move but that takes a trained ear. Now that you know she is a runner you should check out the valve specs. You want it to sound like a well oiled sewing machine. There is always a little topend noise from a well tuned bike of this type.
    No fuel leaking and none flowing out of the back of the carbs, that is great. Again well done.
     
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