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2005 f650CS - loose rear sprocket?

W

wisconsinkris

New member
so i went out to uncover the bike in anticipation of riding to work tomorrow. by chance looked at the rear sprocket and can't help but think that it sure wiggles a lot. is this normal

rearsprok.jpg


moving back and forth in the direction of the arrows the difference is almost 1 cm.

something loose? something worn? is it because it is cold that the seals and rings are allowing it to move so much?
 
Does it move in a sliding motion, or in a wobble motion?

I suspect it wobbles, and I would then be fairly sure that the axle tube has worn and deformed inside the inner races of the two bearings that support the axle tube.

This is based on our experience with an F800S with a belt drive of similar design.

If I am wrong and it is not the axle tube itself, then it would most likely be one or the other of the bearings.
 
Well after some flashlight time and more wobbling it almost looks like its just loose in the area behind the large star nut. Is this something I can back out the large star nut and slide new rings in there?
 
If its the bearings or the tube it is not an easy fix. Its also something that you don't want to ignore or try some half baked fix. If you ignore it, it can hurt you. Get it fixed correctly!
 
Step one is to make sure if it is a wobble in the:

1. Pulley only and not the tube and wheel too.

or

2. The entire tube, wheel flange, and pulley.

The pulley should be a snug fit on splines on the end of the axle tube. If the pulley is loose here then you need to remove the pulley and inspect to see if damaged splines are on the pulley, the tube, or both.

That will tell you what parts need to be replaced.

That is likely to be a 45mm 12 point nut. A 1-13/16 inch wrench or socket will fit.
 
The bike is up on the center stand.

There does not appear to be any wobble in the tire. Only wobble is the rear sprocket/pulley.

Now, to find a socket that big?
 
I'm just asking (but I at least wanted to ask). Does the wheel need to come off to check the pulley.

Can I remove as far as the pulley without taking off the wheel?
 
WisconsinKris said:
I'm just asking (but I at least wanted to ask). Does the wheel need to come off to check the pulley.

Can I remove as far as the pulley without taking off the wheel?
Click to expand...

Yes

Remove the wire clip.
Remove the big nut.
Slide pulley off the spline - given the wobble it ought to come off easily.

Note: The original torque on that nut would have been around 120 ft.lb. It isprobably quite loose given the wobble.

Tightening it up won't fix the spline.
 
Last edited:
I got it all apart and that wobble,I believe, is from a disintegrated seal (8). I'm going to stop by the dealership in the next few days to replace. I saw some other topics about bad shafts and such and got scared. Luckily it appears it is just the seal.

I also noticed the spring clip (11) does not idex in the hole very well, not long enough, so I might as well get a new one too. All the rest is good but i may look into seeing what the yellow parts cost. I believe the bad seal gave it the wobble because (3) wasn't snug and sitting where it should on part (1).

BREAKDOWN.jpg


Oh well, at least I can grease her up while I am in there.
 
WisconsinKris said:
I got it all apart and that wobble,I believe, is from a disintegrated seal (8). I'm going to stop by the dealership in the next few days to replace. I saw some other topics about bad shafts and such and got scared. Luckily it appears it is just the seal.

I also noticed the spring clip (11) does not idex in the hole very well, not long enough, so I might as well get a new one too. All the rest is good but i may look into seeing what the yellow parts cost. I believe the bad seal gave it the wobble because (3) wasn't snug and sitting where it should on part (1).

BREAKDOWN.jpg


Oh well, at least I can grease her up while I am in there.
Click to expand...

If #1 fits snugly on the shaft, but check carefully. I am having trouble seeing how #1 can fit correctly on the shaft and still wobble.
 
With 8 being nothing left but a thread of rubber and a spring ring it allows 3 the room to move away from 1.

I will be bringing the whole ball into the dealer soon for closer exam also.
 
I get it, I think, finally.

If 1 is snug on splines, then 3 with 4 attached is sandwiched by the end load when 10 is tightened.

If parts between 10 and 3 are mangled you lose the axial tension and 3 and 4 wobble.
 
So I brought the sprocket and innards to the local dealership. They graciously, with out hesitation offered to get the parts in and take care of it. I just had to pay for the parts and they would press in the new bearing and such for me.

Five stars for Mischler's BMW in Beaver Dam, WI.
 
Last edited:
Paul,
Is this a service related issue ?
Or is it an engineering design issue ?

I don't have a 800, but I have considered one.
 
This thread is regarding an F650CS. But there is a design issue with the belt drives on the F800S and F800ST - 2007 models. But the defect is not the same as this one. This one appears to me to be a bearing failure.

On the 800s the 2007 models had axle tubes that are too soft. The tube deforms and loosens inside the inner bearing races. The 2008 and later models used a different axle tube and I believe that solved the problem.
 
In conclusion...

New bearing, rubber bumpers and seal in the Drive dog, cranked down to 120 (but had to back it off a hair to get the clip hole to line up) and a new clip to keep it all from spinning loose.

BACK IN BUSINESS. No wobble, belt as snug (or loose) as it should
 
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