Seized primary gear on clutch hub (GS 1000 ST)?

[John Kat]

Some unusual noise was coming out of the RH side of my GS 1000 ST.
At first, I thought it might be coming from the clutch hub nut coming loose but when I opened the right crankcase cover everything was OK?
I pulled the clutch out and discovered that the primary gear on the clutch hub did not move smoothly against it's springs?
Furthermore the springs themselves had traces of wear and they are totally loose in their housing??
Luckily, I have another clutch hub as a spare but is this one repairable?

IMG_0749.jpg

[tom203]

Let's keep this near top... Those guys in southern cali might respond

[Nessism]

Sounds like it's time to grind off the peened over portion of the rivet and pull off the back plate so you can figure out what's going on. It's normal for the spring to wear deep grooves into the aluminum hub so don't be surprised if you see that.

[dorkburger]

The wear marks on the spring are interesting. I wonder if the spring got pushed inside of the backing plate. Following for interest / education.....

[TeamDar]

When the springs start working their way out of the backing plate they usually make contact with the oil pump shaft. The end of the shaft gets peened over and makes removing the oil pump gear difficult. Dar

[londonboards]

When you say the primary gear did not move against the springs ...

Me experience is that you will never be able to move that primary gear against the springs once the clutch has come off the bike. I remember the first time I took a clutch off and examined the primary gear and hub. It was obvious that the springs were some kind of cushioning mechanism and that the primary gear and hub would therefore be able to be rotated independently. But it was impossible to verify this with just your hands twisting them in opposite directions.

I'm guessing you need to pass 80 odd HP through it to be able to feel any movement. So basically, I'm pointing out that you assumption that they are seized may be flawed. They will just appear seized.

The problems with these hubs are that the bigger of the springs (there are bigger ones and smaller ones) get compressed over time and start to rattle about in their sockets. There are various fixes for this, including leaving them alone, putting washers at either end of the springs to compress them and as said above, grinding off the rivets on the backplate, replacing the springs and welding it back up again (sometimes replacing the thin backplate with a thicker one that doesn't warp).

It all depends on your application. For racing, you should replace the springs and the backplate. Clutch explosions and severe engine damage will result at some stage if you don't. However, for most of us, we either find a replacement hub, that is not so badly affected or we put it back in and hope for the best.

Something about the noise you speak about: you can see the springs are loose and that they might rattle around somewhat. But is that the noise you can hear? Mostly I would say that it isn't. The clutch noise most of us hear is a rumble and not the rattle of loose springs (which I figure would by centrifugal force be tightly held to the outside of the hub). This rumble is the whole clutch itself. Yes it can be a loose clutch hub nut but even when it's tightened up fully, there is often a clutch rattle.

See some of my vids on the problem:

https://www.youtube.com/watch?v=Yj6v...yONivII01jQDMT

My opinion is that its usually to do with lateral movement of the clutch hub on the shaft. This is often caused by the fact that the clutch hub spacer is not exactly the same width as the clutch hub. In later GS1150s they came up with a series of shims to alleviate this problem.

I also found (contrary to popular opinion) that the tiny rubber grommet placed in the little hole on the primary gear side of the hub and the oil pump gear spacer stops quite a bit of flapping about noise.

Your problem with the wear on the springs themselves does indicate the severity of their looseness. It looks to me like you need a backplate rebuild or a replacement. Just don't expect that to eliminate that GS clutch rumble you may be hearing.

[John Kat]

When you say the primary gear did not move against the springs ...

Me experience is that you will never be able to move that primary gear against the springs once the clutch has come off the bike. I remember the first time I took a clutch off and examined the primary gear and hub. It was obvious that the springs were some kind of cushioning mechanism and that the primary gear and hub would therefore be able to be rotated independently. But it was impossible to verify this with just your hands twisting them in opposite directions.

I'm guessing you need to pass 80 odd HP through it to be able to feel any movement. So basically, I'm pointing out that you assumption that they are seized may be flawed. They will just appear seized.

The problems with these hubs are that the bigger of the springs (there are bigger ones and smaller ones) get compressed over time and start to rattle about in their sockets. There are various fixes for this, including leaving them alone, putting washers at either end of the springs to compress them and as said above, grinding off the rivets on the backplate, replacing the springs and welding it back up again (sometimes replacing the thin backplate with a thicker one that doesn't warp).

It all depends on your application. For racing, you should replace the springs and the backplate. Clutch explosions and severe engine damage will result at some stage if you don't. However, for most of us, we either find a replacement hub, that is not so badly affected or we put it back in and hope for the best.

Something about the noise you speak about: you can see the springs are loose and that they might rattle around somewhat. But is that the noise you can hear? Mostly I would say that it isn't. The clutch noise most of us hear is a rumble and not the rattle of loose springs (which I figure would by centrifugal force be tightly held to the outside of the hub). This rumble is the whole clutch itself. Yes it can be a loose clutch hub nut but even when it's tightened up fully, there is often a clutch rattle.

See some of my vids on the problem:

https://www.youtube.com/watch?v=Yj6v...yONivII01jQDMT

My opinion is that its usually to do with lateral movement of the clutch hub on the shaft. This is often caused by the fact that the clutch hub spacer is not exactly the same width as the clutch hub. In later GS1150s they came up with a series of shims to alleviate this problem.

I also found (contrary to popular opinion) that the tiny rubber grommet placed in the little hole on the primary gear side of the hub and the oil pump gear spacer stops quite a bit of flapping about noise.

Your problem with the wear on the springs themselves does indicate the severity of their looseness. It looks to me like you need a backplate rebuild or a replacement. Just don't expect that to eliminate that GS clutch rumble you may be hearing.

Hi Richard,
Interestingly enough I had watched your video before posting my issue!
I fully agree with you about the tiny rubber grommet that is there to absorb the vibration coming from the lateral move of the hub as the power is winded up or down.
On my spare hub the primary gear can move ever so slightly against the springs to return to it's default position whereas on the old hub it doesn't move at all despite the springs hanging loose...
I will pull it apart to understand exactly the issue.
Last but not least it's interesting to note that the last clutch steel plate on the GS 1000 ST is in fact a double plate held together by a few rivets.
I'm not sure I understand it's purpose?

[londonboards]

Never seen that riveted plates thing before but all my bike are 1983 onwards. Might have been in earlier models. Have you checked the parts fiche on line.

I'm taking a guess but it was probably to pack out the hub.

[John Kat]

Never seen that riveted plates thing before but all my bike are 1983 onwards. Might have been in earlier models. Have you checked the parts fiche on line.

I'm taking a guess but it was probably to pack out the hub.

The parts fiche doesn't exist on line but I have the french equivalent to the Haynes manual and it can be seen there.
I also have the microfiche but without a reader...
BTW on what side must I grind off the rivets to separate the hub from the primary gear?
Also will the kit from APE (http://gszone.biz/clutches.html) fit the GS 1000 hub?