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XJ motor switch out

Discussion in 'XJ Technical Chat' started by Dstrong77, Feb 25, 2017.

  1. Dstrong77

    Dstrong77 Member

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    I have an 81 xj 650. My shifting fork is bent which as I understand it means that I have to split the cases. I am not qualified to do this and cant find anyone locally to do it for a decent price. So what I was hoping to do is get another motor and switch it out. Then I could study and some day attempt to fix the current motor. my question is would I be able to switch out my 650 for a 750? I know the carb would need to be from a 750 as well. Iam unsure if I would be able to use current driveshaft and electronics. My frame is hardtailed and I have customized this bike to how I want it. I wouldnt want to start over on a whole new bike if possible. Ideas? Also any one know of any motors for sale in the midwest?
     
  2. Toomanybikes

    Toomanybikes Well-Known Member

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    Welcome Dstrog77
    It's a bent fork or is it the shift selector under the cover?
    Just about any 650-700-750 xj motor will fit (650 seca has sold motor mounts)
    Carbs are the same but for jets and needles
     
  3. k-moe

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

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    How do you know that a shift fork is bent?

    What symptoms are occuring?


    Let's talk engine swaps AFTER we figure out if you need to split the case or not (BTW if you can swap an engine you an split an engine case and put it back together).
     
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  4. Dstrong77

    Dstrong77 Member

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  5. Dstrong77

    Dstrong77 Member

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    When I bought the bike it had trouble going from 1st to 2nd. It has forward controls on it and the linkage is good. The clutch has been adjusted numerous times. Over the past couple months while shifting to any gear it has gone into ghost neutrals. Steadily getting worse. Now it will not stay in gear any gear unless rolling on the throttle. As soon as you roll off the throttle it falls out of gear. Ihave been told by 3 different people that it's Gotta Be the shifting Fork. I was hoping it would just be the clutch but everyone is telling me shifting Fork
     
  6. jayrodoh

    jayrodoh YimYam Premium Member

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    Have you pulled the shifter cover as kmoe suggested in your first thread on the issue? Some of the shifter fixes are quite a bit easier than swapping a motor.
     
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  7. k-moe

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

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    So OP, did you look? Your last post was about draining the oil, and we haven't heard a thing since.
    http://www.xjbikes.com/forums/threads/81-xj650-shifting-fork-or-clutch-issue.106900/#post-548993

    Three people telling you the solution, without diagnosing the problem, is nothing more than random guesswork.

    You want this solved. We want this solved. Ideally both can happen with the least amount of expense and effort, but only if we work together.
     
    Last edited: Feb 25, 2017
  8. Dstrong77

    Dstrong77 Member

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    I think i will need to investigate that further no springs were br
    For sure. I got the oil changed. I did open the shifter cover as well as the clutch basket no obvious damage.
     
  9. k-moe

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

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    When you had it off, did you pop the shift lever back on and watch the shift drum as it turned?
    IIRC a few members have had simmilar problems to yours that turned out to be a worn bushing.

    Since you have the problem in all gears it really is making me think that it's either a shift selector issue (fairly asy to remedy), or worn gear dogs (less eassy), or that your alternator chain guide is in peices (see link below) and preventing the gears from getting fully into position (also less easy, but there is a temporary fix tht will buy you time).
    emergency guidectomy

    A bent shift fork would only effect the operation of two gears.
     
  10. Dstrong77

    Dstrong77 Member

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    wow thank you K-Moe That would be awesome if it was the shift selector or the alternator Chain guide. worn dogs has been mentioned but I did not know that the shift fork would only affect 2 gears. I didn't watch the shift drum I only looked for obvious damage I never even tried to shift it when the cover was off. I will open it back up and take video. I am not sure if I am going to know if its operating properly anyway. I truly appreciate the advice. I will report back!
     
  11. k-moe

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

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    If it's operting properly the wheel that holds the shift drum will drop into each detent on the drum with a snap.
    Be sure to shine a light through the inspection holes and look for chunks of plastic. You can also see (if you have good eyes and maybe a inspection mirror) the shift forks.
     
  12. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    INTERNAL SHIFTER MECHANISM PARTS:

    Inside your shifter case side cover are a variety of levers and linkages that translate the motion of the your shifter foot pedal into movements that operate the SHIFTER DRUM, which in turn operates the SHIFTER FORKS which then engage or disengage the various TRANSMISSION DRIVE GEARS. Worn or damaged RETURN SPRINGS can prevent the shifter from operating properly, and are the first thing to check if your bike will not go into gear, is "stuck" in a particular gear, or if you cannot "find neutral".

    Of course, there may other issues which could cause the same problems, particularly the dreaded "disintegrating primary chain guide" issue, but it's always best to determine whether a simple problem exists first..........

    Pictures of the inside of the shifter assembly can be seen at:

    http://xjbikes.com/forums/index.php?threads/20246

    and

    http://xjbikes.com/forums/index.php?threads/28233


    A good write-up on the typical problems and issues involved with these parts can be accessed at:

    http://xjbikes.com/forums/threads/xj550-transmission-problem.12233/

    http://xjbikes.com/forums/index.php?threads/19227

    http://xjbikes.com/forums/index.php?threads/48591

    However, please note that the exploded diagram attachment on the 19227 page is "typical" for most XJ-series bikes, the actual mechanisms will differ slightly between different models (the diagram shown in the 3rd post is correct for the XJ650 - XJ900 models; most other models use a variation on the same theme).

    NOTE: if this describes your situation:

    Couldn't get her out of (whichever gear you were in when the problem occurred).

    This situation can be caused wither by a broken TENSION SPRING (the small linear-acting spring) or by the TORSION SPRING (the one with one straight arm and one "hooked" arm). Both of these springs are designed to keep the pawl arm properly engaged with the shifter drum "star wheel" segment. Note there is also a long SCREW which retains this star wheel to the shifter drum; if that screw is loose, it will allow the star wheel to rock back and forth or not even engage with the drum, also resulting in the same type of issue.

    On early XJ650 engines and XJ750 Seca engines, the original torsion spring used was somewhat weak, and was replaced by an upgraded spring on later model engines, which also required a slightly different spring collar (sleeve) to be fitted.


    NOTE: if this describes your situation:

    "Today, after a downshift, the shift pedal would not pop back up automatically."

    This problem tends to be caused by a broken TORSION SPRING (the one with straight arms on both ends of the spring) which is supposed to center the selector shaft segment. The earlier 1980-81 XJ650 and XJ750 Seca models were especially susceptible to this problem, and an upgraded, thicker spring (which required a thinner spacer collar underneath) was introduced to the 1982-later models.


    Of course, some of these issues may be due to something as simple as broken shifter mechanism but it also could be dues to worn gears (see the TRANSMISSION: section further below for details) or the dreaded "disintegrating primary chain guide" issue, but it's always best to determine whether a simple problem exists first..........
     
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  13. Toomanybikes

    Toomanybikes Well-Known Member

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    image.jpg IMG_0891.JPG View attachment 24115 If the little wheel indicated at tip of pen it second pics is not holding the shift drum (with a spring) first pic in place as it shifts to each gear, the drum "wanders " and transmission will not stay in gear
     
    Last edited: Feb 25, 2017
  14. k-moe

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

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    Under #1 there is a fairly large hairpin spring that centers the shif mechinisim. Sometimes they break. There should be (on most years) a large bushing that keeps the spring centered. Earlier bikes had a smaller, and weaker centering spring, and no bushing.
    A #2 you'll see the obcious spring that returns the shifting pawl to its "idle" position. Sometiems they weaken with age (or break).
    At the top if the shifting pawl there is a small hooked-end coil spring. That is also subjec to breakage, or becoming unhooked.
     
  15. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    It seems that images have changed, and now the #1/#2 indications are reversed.....so k-moe's response above no longer applies(?).

    The "forward" shaft assembly (closest to the drum) has a large "hairclip" spring (one arm has a "hook" end) which keeps tension on the "stopper assembly" which is the arm at the bottom of the shift drum with the "3 points" on it.

    The "rear" shaft assembly also has a large hairclip type spring (both arms are straight) and this is the spring which has the collar underneath it.


    The pen tip in the "new" images above are both pointing to the dowel pin (and not the pivoting "stopper assembly") as in the previous images.
     
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  16. Toomanybikes

    Toomanybikes Well-Known Member

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    IMG_0890.JPG
    Oops I put same pic twice, it was late. This is other pic I meant to use
     
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  17. Dstrong77

    Dstrong77 Member

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    Wow this is so helpful! I will read this over a few times and open it up. You guys have been great I will inspect it further and report back. Thanks!
     
  18. k-moe

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

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    I was refrencing the numbers in the photo, and should have been clear about that.
     
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  19. Toomanybikes

    Toomanybikes Well-Known Member

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    I think with all the info here he gets the jist of what we are saying:)
    Anything floppy is broken
     
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  20. cds1984

    cds1984 Active Member

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    I reckon... if you have the nouse to pull an engine out and put it back in again... your not far off from being able to do surgery on it also.
    and... since your thinking of swapping it out surely you have very little to lose, splitting the engine if need be... that is if none of the above suggestions work out for you.
    My 2 cents worth.
     

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