1. Hello Guest. You have limited privileges and you can't "SEARCH" the forums. Please "Log In" or "Sign Up" for additional functionality. Click HERE to proceed.

Xj 750 82 maxim blowing main fuse while igniting

Discussion in 'XJ Technical Chat' started by Laurensvdm, Mar 17, 2022.

  1. Laurensvdm

    Laurensvdm New Member

    Messages:
    25
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Belgium
    Hi Everyone,

    I bought a 82 xj 750 Maxim in pieces as a project. Owner said it was running when he took it apart. I have no experience with working on motorbikes. (only riding them)

    I want to see if the engine starts and runs before i buy new parts for the makeover to caferacer. So i started by putting the engine in the frame and checking out all the electrics. There are some weird wirings but most seems fine. When i connected everything the lights and blinkers would work after i put my keys and put it ON.

    When pressing the RUN symbol i hear the cut off relay clicking and when pressing IGNITE the main fuse burns out. I also hear the starter working for one milisecond.
    The main fuse is a 20A one close to my battery. Not the main fuse from the fuse box.

    I started pulling out things in the circuit to see what gives me a short circuit.
    Currently no lights are connected and the rectifier is also off. So only the basic ignition parts are connected. However i still get the fuse blowing part.

    Bike is in neutral and i grounded the neutral wire.

    No kickstand or clutch switch are connected.

    I think its something obvious for an experienced motorbike technician. However for me..

    I tested the starter relay seperately : measured it out and it clicks also.
    Also i think it works because i hear the starter when pressing IGNITE.

    Battery is ok, bought a new one.

    Today ill try to do tests on all the connected parts seperately to see if one is damaged.
    But if someone could point me in the right direction that would be awesome!

    Ive been thinking on redoing the whole harnass but i think it will give me much more work and costs in the end..
     
  2. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

    Messages:
    1,177
    Likes Received:
    568
    Trophy Points:
    113
    Location:
    Minneapolis, MN
    Sounds like you just have to work your way through the possible causes of the short circuit - sounds like you have gotten a good start.

    One part that seems strange to me is that you said the rectifier is off. Not sure if that would cause your problem or not, but seems strange. Do you have the TCI unit connected?
     
  3. XJ550H

    XJ550H Well-Known Member Premium Member

    Messages:
    13,199
    Likes Received:
    3,854
    Trophy Points:
    113
    Location:
    Great North Woods
    there is only 1 main fuse battery positive runs to solinoid and a second wire from the battery runs to the main fuse.
    then from main fuse to ignition key when you turn on the ignition key it sends power back to the other 3 fuses .
    serch this site for minimum wiring diagram it will show you how to wire ignition system to start bike motor
     
  4. Laurensvdm

    Laurensvdm New Member

    Messages:
    25
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Belgium
    Okay i think i'm on the right track :)
    I tested my coils again : primary measurements were around 2.5Ohms and secondary around 12.5k Ohms. -> Okay


    I narrowed it down to the following :

    Battery , starter solenoid & starter motor.
    Red from battery to red from starter solenoid. ( in between i place a 20A fuse )
    Then black cable from starter solenoid to starter motor.
    Then from the frame black to the negative side of the battery.
    It all makes good connection. I tested it for resistance.

    When shorting the starter solenoid ( with a piece of metal so current can flow ) , i hear the starter motor for a bit.
    Then directly the fuse blows

    Now what does this means ?? o_Oo_O
     
  5. Fuller56

    Fuller56 Well-Known Member

    Messages:
    760
    Likes Received:
    345
    Trophy Points:
    63
    Location:
    Cary, NC (winter) Harpursville, NY (summer)
    My first thought is the starter motor has a problem, drawing too much current to turn. Next step is to take it out of the motorcycle and test it on the bench. It could have bad bearings or just need to be rebuilt. XJ4EVER has kits to do this, if needed.
     
  6. Rooster53

    Rooster53 Well-Known Member Premium Member

    Messages:
    1,852
    Likes Received:
    723
    Trophy Points:
    113
    Location:
    North, FL
    If I understand that correctly you have a 20 amp fuse trying to power the starter, that's not going to happen and it's going to blow. There should be a direct (large wire) between the battery and the starter solenoid

    Here is a link for the Maxim showing the hookup for the positive lead

    https://www.ebay.com/itm/304396462922?hash=item46df716b4a:g:AIkAAOSwlitiLnoh
     
    Last edited: Mar 18, 2022
    chacal likes this.
  7. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

    Messages:
    8,866
    Likes Received:
    1,780
    Trophy Points:
    113
    Location:
    The room where it happened
    Yep, as Rooster53 says, the starter motor draws a LOT of current, and in the stock electrical systems, is not fuse-protected.
     
  8. Laurensvdm

    Laurensvdm New Member

    Messages:
    25
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Belgium
    Thanks for the answers !
    I figured it out also yesterday that the startermotor indeed draws alot of current so makes no sense to fuse it! Rookie mistake :)
    Removed the fuse and hooked everything up again..
    Got the engine running for the first time and damn it felt and sounded good !:D
    Learned alot about the electric parts, now time to start assembling it and ordering parts for the caferacer look :cool::cool:

    Thread may be closed.
     
  9. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

    Messages:
    1,177
    Likes Received:
    568
    Trophy Points:
    113
    Location:
    Minneapolis, MN
    Alright! Good job!
     

Share This Page