It is easy enough to remove the bearing and to check it for play on the bench. If it's not buggered, you know what to do! If it is you also know what to do - and half the job is done now it is out!

The assembly has 2 different styles of bearing so it can be difficult to feel play or hear it unless under particular circumstances in which they're under load/the play is causing them to work as not intended.

 

Thank you for your response! Is there anything in particular I should know about checking the play? My plan was to remove the eccentric assembly from the bike and test it for axial and radial play (albeit by hand)

 

Yup, that's the way i did it. It is easier to feel the play when in hand and also to hear from which section the noise is coming from.

 

Update: for anyone with similar symptoms as I had.

so yesterday I took apart my STs drive axle. To start things off.. the 46mm Nut that holds the rear pulley on was practically seized on there. I heated up the nut to loosen the thread lock but the physical threads themselves were in a condition I had yet to encounter (mind you I work on cars for a living). After seriously struggling and having to alternate use of an impact driver and a 2 meter breaker bar I eventually was able to remove that sucker.

going to remove the eccentric drive axle was.. an adventure. I could tell after removing the rear pulley that it itself had no play because the back and front plates had zero movement. The drive axle on the other hand.. that was not only noisy but now really loose since it had no load on it.

despite plenty of penetrating lubricant and heat, removing the drive axle was a laborious and loud endeavour. I had to resort to using hearing protection because of how much I had to bang on that thing to get it to move. I was unable to move the eccentric using the pin since this guy was completely seized in place.
Long story short; new drive axle has been ordered and today I’m going to clean the bore the eccentric sits in.

So to anyone who has any play in their rear wheel AND is unable to adjust your eccentric…

make sure you have a spray can full of WD-40, a torch, and a hefty hammer. Good luck!

 

How did you remove the rear pulley?

Did you put it in first with the belt still on and then use the impact/breaker bar?

I have a slightly wiggly rear pulley that might require tension but all this considered, might be a good time to replace the rubber cushions.

 

I have some play in the rear belt pulley, and when grabbing the wheel at 12 and 6 I can hear and feel a light “clunk” indicating play in the wheel, but it’s so small it’s barely visible. Whilst I had the wheel off today I spread the brake pads and turned the belt pulley and found literally no noise other than belt noise.. I then put everything back together, started the bike and on the centre stand put her in first gear. Watching the belt I can see it moves minimally towards the outside of the pulley, and when parked up against a wall I can hear what I equate to the “mechanical stumbling” that you might hear from a cars differential that has too much play.. that’s what’s confusing me because on one hand the bearing sounds fine (wheel off, pads spread, rotated by hand) but on the other hand I can hear bearing rumbling when using the motor to power the wheel.

At this point I’m thinking I either need a new eccentric

You might find this post interesting...

https://www.f800riders.org/threads/belt-adjustment.324914/#post-2918997

I had a 2014 GT. Loved it, and still miss it. If you read the post above, you'll find one of my rear wheel bearings disintegrated inside the hub and the other froze. I think my guardian angel was working overtime that day.

That GT had 97000 miles when the bearing failed. I purchased a used rear hub and eccentric on eBay for $299. It seemed like a good deal. The seller couldn't tell me how many miles the bike had, because it had been wrecked in the front and the instrument panel wasn't working. Okay. Almost any other bike would have far less miles than mine had, so I felt safe with the purchase.

But whereas before the failure I had only looked at the belt for it failing like cracks, I was looking at it far more than before. I noticed after a few more miles that the belt was tracking to the outside of the pulley. Hmmm....I'm kinda anal about things like this, so I kept researching and trying to figure out why.

I came across the checks in the BMW recall for the ST. BTW, the replacement part to install, was what I already had in my GT that had failed. The first thing on the recall checklist to check was where the belt was tracking. Mine was tracking to the outside, which they said meant you needed to do more checks. Like you, I did the check at 12 and 6. I bought a mechanic's stethoscope and couldn't hear any noise inside (this is on the "new" hub).

We had some cousins of my wife come over for dinner and I mentioned that I didn't feel comfortable with the rear hub and bearings. She was in the kitchen at the time, but overheard our discussion. About that time, a friend who retired from Caterpillar said they would replace the belt and it would then track correctly. It didn't make any sense...it's a kevlar belt...but I tried it anyway -- and the belt tracked to the inside as it should. So I felt better at that point and was going to just keep a close eye on it.

But my wife told me after the cousins left to sell the bike and get a new one. Being a good husband, I complied.

And so I don't know if the used replacement had solved the problem, or if I should've done like you did and buy a new one.

I wish the best for you.

Chris

 

Thank you for your response!

as far as I can ascertain from my colleagues in the two wheel department, the replacement for ALL S/ST/GT eccentric is basically what you get from the factory in the GTs. Besides the eccentric bearings themselves, belt tension plays a big role in the wear on them. I’ve been told that the way BMW wants you to do it up is too tight, and thus what is recommended by them unofficially is setting the belt play to around 6mm of up and down play in the belt, or such that there is little to no tracking of the belt.

I’ve also however been advised to not be too anal about the rear pulley and belt tracking though - what some perceive as tracking is actually one of two things; the pulley assembly doing what it should and the pulley itself not being 100% “round”.
Oscillations in the belt side to side up to 1mm are okay - anything beyond that indicates an issue.
I like the ST.. but this experience has soured it for me. It’s going to get traded in for either a GS or a 1200RS in the near future.