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1983 XJ750 Maxim Build (Updates and Questions)

Discussion in 'XJ Technical Chat' started by XJ750DB, Dec 16, 2017.

  1. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Pull the rotor. My guess is that the debris damaged the rotor windings.
     
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  2. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Check the rotor resistance at the copper rings.....red probe on one of them, black probe on the other, doesn't matter which ring is which (inner or outer).
     
  3. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    I am mildly surprised… I have never had a stator go bad on an xj. I know others have… But I have only ever had regulators fail
     
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  4. XJ750DB

    XJ750DB Member

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    I cleaned the commutator rings and tried to get a reading on the rotor. I could not get a good reading. I would just go up and down and did not stop on a number for the resistance. The inner ring is pretty scratched up too.

    Tomorrow I will pick up a 16 x 1.5mm bolt to pull the rotor and inspect it.
     
  5. XJ750DB

    XJ750DB Member

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    After I pulled the rotor I cleaned the communicator rings some more and I was able to get a good reading with the rotor in spec. I replaced the brushes and stator and now the charging system is functioning properly. I cleaned and added dielectric grease to every connector on the bike and found another wire that had been getting warm.

    It is the red wire on the large connector. I believe this wire is for the rectifier.

    I am still having the same issues with the idle. Is there anything else I need to check to fix the hanging/rising idle?
    I have not found any vacuum leaks.
     

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  6. WesternMeadows

    WesternMeadows New Member

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    Just wanted to mention that white smoke can indicate aluminum burning. Might be your piston rings wearing as I had a problem with oil burning on my XL500r. What I believe happen is the piston rings were damaged when my oil drain plug fell out while i was riding. After I got a new drain plug oil began blowing past the piston head and out the exhaust. Its possible that this may be happening in your bike if your seeing white smoke. It is possible the piston rings burning and wearing. This is a fairly serious problem as this eventually lead to my piston head burning and breaking apart in my XL500r cylinder.
     
  7. XJ750DB

    XJ750DB Member

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    I finally got the bike idling correctly. I ended up going through the carbs with a fine tooth comb to look for anything out of place. I ended up finding 2 tiny little pin holes in #1&4 carbs. I sealed the holes with plastidip and reassembled the carbs. I put the carbs back on and the idle still wanted to climb to 3000 rpms.

    I took the bike for a 15 minute ride and set the idle. With the engine warm i set it at ~1500 rpm.
    I then ran a vacuum sync and the hanging disappeared. I followed up with the colortune and another vacuum sync. During the color tune #4 was misfiring pretty bad.

    The bike is idling great now but will not start without the choke on. After 5 minutes of running I can turn the choke off and it will idle. It does this cold mornings or when the bike is hot in the afternoon.

    The clutch is definitely starting to slip but I hope I can wait till the winter to replace it. Otherwise the bike rides great! Thanks to everyone for all the help.

    Big shout out to Len at XJ4ever for all of the parts and information I would not have gotten this far without the info from him and this site. 20180718_175745.jpg 20180718_175927.jpg 20180718_175940.jpg
     
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  8. XJ750DB

    XJ750DB Member

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    Well the bike left me stranded today. After putting about 600 miles on the whole rebuild the battery stopped charging.

    During the rebuild I replaced the stator with a used but in spec stator. I also cleaned the commutator rings on the rotor and installed new brushes. The bike ran find for the past 600 miles never needing to charge the battery.

    Today I rode to the gym without any issues. While I was inside the bike got rained on, the rain didn't appear to get on any of the electrical components so I went on my way. At the end of the ride the bike started to misfire and sputter under acceleration. I parked the bike for a couple hours before I tried starting it again.

    The bike was completely dead when I tried to start it again. I pressed the starter and it didn't have enough power to start the engine. I was able to bumpstart the engine but it only got a few blocks before dying again.

    I checked the resistance on the stator and I got, 0.9,0.7,0.7 across the 3 wires.

    The is the second stator I have gone through. What else needs to be checked?
     
  9. Rooster53

    Rooster53 Well-Known Member Premium Member

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    That is a bit high for the stator, but sometimes it's hard to get a good connection and get the DMM to read that low of a resistance.

    Check the brush / field coil connection at the two pin connector (Br - G wires) to see how close to the 4 ohm spec you get.

    Make sure the battery is good. Is it a wet cell, does it have water in it? Will it charge and hold a charge? Once charged, will it maintain a 10V level when the bike is cranking.
     
  10. XJ750DB

    XJ750DB Member

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    I charged the battery overnight and brought it in to a auto parts store to have it tested. It tested good.

    I checked the field coil and could not get a resistance reading across the connector. I pulled the alternator cover and checked across the two commutator rings and still could not get a reading.
    I pulled the rotor and found that on one side the potting material has come off and exposed the wire. Is it safe to assume the rotor is toasted?
    20180809_125451.jpg

    I also checked the rec/reg and everything was in spec. Next I checked for any parasitic battery drain and I could not find any drain.

    Finally I started the bike and got a voltage reading around 11v while cranking. As I brought the RPMs up the voltage did rise to 13v indicating that the battery is charging.
     
  11. Rooster53

    Rooster53 Well-Known Member Premium Member

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    Normally with no reading across the commutator rings yes it would be toast. The only exception might be is if the solder joint has failed on one of the terminals (not likely) it might be savable.

    It that with the original field coil or with a different one? With a fully charged battery you should get a voltage of 14.5 +/- .3V at 2K rpm and up.
     
  12. XJ750DB

    XJ750DB Member

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    That is with the original field coil.
     
  13. Rooster53

    Rooster53 Well-Known Member Premium Member

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    So maybe I'm confused, is the field coil still ohming open across the commutator rings, and if so why even try it?
     
  14. XJ750DB

    XJ750DB Member

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    Sorry for the confusion. The field coil was still ohming open across the rings when I tested it. The only reason I tried it is because I needed to ride it home. With a fully charged battery I was able to get ride the bike 20 miles home. I had no way to tow the bike and it was getting a charge intermittently.

    Thanks to Joe Elliff I have replacement parts on the way. Those should resolve my charging issues.
     
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  15. XJ750DB

    XJ750DB Member

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    I have been having issues with my clutch slipping under acceleration so I replaced the friction discs, springs, screws, and washers.

    With the cable adjusted to achieve maximum throw I never can get enough free play in the lever it seems. I have read big fitz's clutch adjustment write up several times moving the pivot arm tooth by tooth.

    I have checked my plain discs for flatness but cannot find a wear thickness limit. Does anyone have the spec for that?

    I am running shell rotella t4 15w-40 oil.

    The inner and outer basket are also showing some wear. Is this acceptable? 20180815_174224.jpg 20180815_174228.jpg 20180815_174232.jpg 20180815_174221.jpg
     

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