Drive shaft to final drive.

Hey all...I just dropped the engine back in my xj650 and I’m having an issue. I connected the engine to final drive from the rear wheel and it moves but it catches and “shifts/bumps” the engine. I can push it thru this catch but clearly doesn’t seem right.

I know I’m in neutral

I know my engine is not siezed (I can spin the engine drive just fine and also push around the bike just fine while not connected to the engine

I have filled all the fluids including adding some sae 80 hypoid oil to the final drive And where the engine and final drive connect.

the only thing that’s different is I have an r1 front fork on...could that change the angle and make it catch like it does?

or any know what I’m doing wrong???

thanks
Chris

 

the angle of the swingarm, with the U joint inside it can't be too far from original.
the U joint might be binding

 

That’s prolly it! Awesome. How do i change that? Lower my shocks?

 

lower the back or raise the front. don't think there is a easy way to lower your shocks, going to need shorter ones. HD maybe

 

Right. I bought progressive 412 that I should be able to adjust. So if i extend my shocks that will push the swing arm down right?

 

1. Are you sure the drive shaft is in the ujoint correctly

2. are you sure the ujoint isn’t seized?

 

tie the back of the frame to the swingarm and pull the frame down 2 or 3 inches and do the wheel spin thing again

 

Well I never disconnected the u joint. I left the swing arm attached the whole time. and if the u joint was off or seized wouldn’t that affect just rolling the bike around normally.

 

Just starting to check the obvious and work our way in

 

Are the replacement shocks the same length? As previously mentioned there is not a lot of range to change the rear geometry. Do you still have the originals to compare?

Doesn't matter what front end, even without a front end on the bike the rear geometry won't change unless you change the shock length or travel.

 

haha I didn’t mean my comment in a mean way. I was more talking out loud and if my thought process was wrong you could correct me.

 

ill check but the bolt holes just lined right up. And I bought them because they fit my bike. What I’m struggling with is that even with the engine and not connected to the final drive...I can move the bike around and I don’t feel or hear the unjointed catching. It’s only when I bolt them together that it does it

 

I may be mis-understanding, but is your joint bolted to the engine or not.....

if it is, and the catching happens only in gear, then it would SEEM to be a transmission issue at this point.

if it is not, and it rolls fine, but catches when you bolt it together, then that would SEEM to indicate a seized u-joint, or a driveshaft not in the u-joint correctly, or a problem in the final drive, or possibly missing the spacer inside the hub, or a rear brakes issue........lots of possibilities.

we have to narrow it down to locate which side of the u-joint the actual issue is on.

 

So lets just start from the beginning so it all makes sense (hopefully)...I put the rear tire back on about a week ago without the engine and it moved around just fine..I then put the engine back in the bike and attached the rear brake and it moves just fine. I then attach the engine to the final drive and it catches/ bumps the engine...I did lower my springs and that did make a difference but it still catches... even if I sat on the bike and move it around and it still catches/bumps the engine. I do have the sae 80 hypoid oil in and to the proper level...I could drain that one completely I guess???

so if it was the brake was the issue wouldn't it catch/bump regardless of whether or not the engine was attached? I know I put the spacer inside the hub ( but again wouldn't it still catch/bump whether or not the engine was attached?) I'm asking to make sure...

All I did to attach the engine to the final drive was use those four bolts...I am not the one who pulled the engine but I know the engine shaft moves freely ( I can spin it when not attached to the final drive and the bike moves freely when not attached which should mean the ujoint isnt seized...correct? again asking to make sure...

do I need to attach those 4 bolts in a specific way?

thanks so much!

 

Since you are not the one that removed the motor in the first place, I wonder if you have the correct bolts for the U-Joint connection to the motor. If one or more was too long I can see it interfering with the motor. Maybe peel that rubber boot back and have a friend spin the rear wheel while you watch. Should be easy enough on the center stand.

I'm assuming when you say "bumps the engine" you mean it is physically moving the motor around? If you mean it is turning the engine over than I (we) are thinking of something different.

 

yes the engine physically moves up and down...haha and yes 2 of the 4 bolts are different...but the length difference is 2/16...could that small of a difference really be causing it?

 

So 1/8"? I don't know the clearances off top of my head but knowing that there are two different bolts I would be suspect. If it is the issue and the motor is physically moving up/down, you will definitely see some evidence/markings on the motor case.

 

Haha yea an 1/8. Lol good times. As in marks I don’t see any really and if you’re talking on the inside of boot the bolts go in from the engine side and screw into the threaded final drive flange.

But I can see the engine go up and down/rock...

I’ll be honest you are taking to a rookie...this was my first build bike and a way to really learn more about the bike and how everything works. So if you’re saying something and I’m misunderstanding it’s totally me lol.

 

Sorry, I had that backwards. Has been awhile since I installed a motor. It's the only place I can think of for something to be knocking the motor around like that, either a bolt is too long and it's hitting the UJoint assembly, of the joint is bad. DO what I mentioned earlier and watch that joint while someone spins the wheel.

 

I’m still focused on the ujoint installation or drive shaft installation. Still seems to me that the drive shaft may not be in correctly. But, if you didn’t remove it, then that should eliminate that possibility... I’ll leave it here in even it’s a PO thing?
Would it catch when the engine is in gear? YES, the U-joint tries to turn and interferes with a drive shaft NEXT to it.

would it roll freely in neutral? YES, because the drive shaft is just a straight shaft rotating in the space it occupies. The u-joint isn’t trying to turn, because it’s IN NEUTRAL.

what you need to do is:
-put the bike on the center stand.
-pull the boot away from the SWINGARM and verify that the shaft is IN the ujoint
-in neutral, spin the back tire to verify the shaft and u-joint are turning properly. If ALL of that is good, then it’s either the joint itself, or inside the engine/tranny.

Now, if you didn’t bolt the ujoint up correctly, well then—-

The 4 bolts that hold the u-joint in place would have to be really long to interfere with the rest of the u-joint. It does not “flop” that far sideways.

if it is a bolt issue, then my bet is that you have the bolts in wrong. The bolts go in from the ENGINE SIDE. If the bolts are too long, you won’t get them in in the first place. The U-JOINT HAS THE THREADS. If you put them on from the swingarm side, they are not drawing anything together.

 

Thanks for all your help with the bike and input...sort of at standstill right now...hopefully, I will get to the bike soon and will be able to look at all your ideas and thoughts. Ill do my best to keep you updated.
Thanks