XJ motor switch out

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?

 

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

 

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).

 

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

 

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.

 

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.

 

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.

 

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.

 

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!

 

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.

 

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..........

 

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

 

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.

 

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.

 

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

 

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!

 

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

 

I think with all the info here he gets the jist of what we are saying
Anything floppy is broken

 

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.

 

IMHO a used engine is going to need to be split too. Replace the 30+ year-old alternator chain guide, and rebuild the starter clutch before either give any trouble.

 

I have the shifter cover off it appears the stopper is not operating properly it's somewhat shifts up but is really hard to shifts down. The spring on the rear shaft with the loop is not connected and spins around easily. I have inspected the hole above shift drum and there is no plastic impeading movement. Will post video and pics

 

I have a video i will post on YouTube and het link

 

Any suggestions?

 

Looks like a broken torsion spring!

 

The gears have to be moving in order to shift (until all the gears line up). There are no synchronizers.

The little roller is supposed to be touching the shift drum, but is not.
That broken spring will cause the problem you have.
Chacal has replacements in stock. Start a conversation with him and you can be riding before next weekend.

 

Well Im bout as happy as I could be. I think ill get replacement friction plates since the oil is out.
You guys have been so helpful! I am so thankful! I will reach out to Chacal. Thanks again everyone

 

Ok I have my spring installed and the arm is working properly. I am attaching a picture of the position of the shift drum in the position that I believe is neutral. I cannot find a diagram that shows what position it should be in. Once the spring is installed I have the same issue that I have had since I got the bike. It is hard to go into gear. I believe since it was hard to go in gear for so long I had been stomping up and down on the control that is how I ended up breaking the spring. When I shift to first I can usually get it to go with a few clicks. Bringing it up to second is a challenge because I feel it click as I up shift however it doesn't actually engage unless I keep trying then eventually it will. Which makes me think its internal again. Either shift forks or worn dogs. I have not reassembled it yet as I am interested to see if my shift drum is in the correct position for neutral right now (pic) Would anyone be able to tell from this pic if the shift drum is in the correct position for netural. I will take another video tonight to show whats going on. The outside of the shift drum where the stopper pushes against has some larger rounded tabs and then 2 smaller rounded tabs. I believe the space between the smaller tabs is neutral, The wheel spins freely there. I am able to shift down and the gear engages from that neutral position however getting up past that neutral position to the gear above is where my trouble lies. Any suggestions?

 

I'm sure someone who is more familiar can say for certain, but I believe that is neutral. Just looking at how mine was from when I was tearing my engine down it appears correct. Are you able to spin the transmission in between shifts? It needs to advance a little between changes to allow the roller and selector to engage before advancing to another gear. Your grooves there do look a little worn, but I don't think it would cause too much, if any, trouble.

 

yes it does move between shifts. Ill get the video up tonight to show exactly whats up. From your pic would you be in 1st gear there?

 

I didn't take note to be sure, but I believe that it is in first gear in the picture.

 

Correct.

Make sure that you are moving the rear wheel a bit when you are trying to shift. As I mentioned before the gears do not have synchronizers, and will not shift unless they are moving so they can line up properly. Once they are all lined up the transmission will shift freely without needing to move the rear wheel.

I'm looking forward to the video so we can see what's going on. Get as close in as you can so we can see what the shift drum and pawl do as you move the lever.

 

Once I put everything back together and tried shifting with the forward controls I wasn't getting enough torque on the shifting lever with my forward controls I was able to shift fairly easily without the linkage just using my hand. i'm reassembling now, putting oil in it and tightening those linkages as far as possible.
Now I believe loose linkages on the forward controls cause me to overwork that torsion spring on the pawl stop. I do not have the original shifting lever otherwise I would just put that on and test it on the road but I feel pretty good about it now and will report back tomorrow. And yes checking the linkages was the first thing suggested when I came to this forum with my problem. I tightened all the screws originally but I did not extend the adjustable linkage to make it tighter I have done that now and will see how it goes. If not I'll pull the cover off and get video. If you look at the original video I posted you might be able to tell how much play was in the forward control

 

I just got back. It was absolutely the linkage. Bike shifts like a dream now. Thank you for all your help. I truly appreciate it!

 

The linkage wouldn't have caused the spring to break. The shifing mechanism has ravel limits built into it. The spring broke because it was old and had been through all of the cycles that it could take.

 

True but since there was so much play in the linkage it caused me to stomp on the controls to get it to engage the gears. Which added to the old worn spring finally breaking. I think had i tightened the linkage when i bought the bike i could of prolonged the springs life. Maybe not.
Now everything is tight and i can shift with much less force. I am back in love with this bike. On a seperate note. I rebuilt the carburetor about a month ago. I changed out one of the Jets and the jet that was in the rebuild kit had a different number and then the one that was in my carburetor. I believe since I have a 4 into 1 exhaust that it was jetted. Now I have backfire when letting off the throttle in low gears. I think I'm going to need to open up the carbs and stick the other jet in. There was no backfiring before I rebuilt it. At that point I didn't know different exhaust would require new jets that werent in the kit. Lesson learned

 

Ya, rejetting is needed. You are lean on the pilot circuit.