Clutch fiction disk blew up, again.

ILikeBigBikesMan

Joined
Dec 18, 2025
Messages
13
Age
29
Location
Colorado
Bike
St1300
Hello. 6 month ago some of my 2003 st1300 clutch friction disks shattered into many pieces while ridding. I made post about it here. https://www.st-owners.com/forums/threads/clutch-friction-disk-disintegrated-why.190847/ Now 6 months later it has happened again. I took it apart and the friction disk had the same problem. It completely fused to the steel plate, I assume from heat. One thing I noticed is that the friction disks seem dry, one seems incredibly dry. I have uploaded a picture of that particular disk. It feels dry to the touch and I think it even looks dry in the picture. These are supposed to be constantly bathed in oil right? It seems like the clutch area is not directly connected to the oil drain pain because in the drain pan that section is partitioned away from the main area. Is there something that squirts oil into the clutch area, or some sort of lubrication system I should try and diagnose. Thank you, any info would be super helpful.

This first pic shows the broken friction disk along with a very dry friction disk.
The second pic is just the clutch area, if its at all helpful.
 

Attachments

  • 20260621_123826.jpg
    20260621_123826.jpg
    111.6 KB · Views: 22
  • 20260621_124756.jpg
    20260621_124756.jpg
    198.2 KB · Views: 23
Are you doing a lot of low speed maneuvers, like the cops like to do.

It looks similar to the clutch I removed from the ex cop bike I took the engine out of to put in the AZ05 ST1300, although there were no broken clutch parts.

20250403_CopClutch-burnt.jpg
 
SupraSabre said:
Are you doing a lot of low speed maneuvers, like the cops like to do.

It looks similar to the clutch I removed from the ex cop bike I took the engine out of to put in the AZ05 ST1300, although there were no broken clutch parts.

20250403_CopClutch-burnt.jpg
Click to expand...
Yeah, well. I was again doing low speed u turns. I'm willing to concede that I just have poor technique if you convince me. I try to make them fairly tight and rev the engine to around 4k rmp using the clutch to control speed. I'll admit I drag that rear brake a little, perhaps too much? I only did around 20 u turns before the thing blew up. I can only imagine that the police officers when training abuse the clutch far more then that and these things are expected to handle it right? Perhaps I'm just destroying my clutch, but that friction plate is really dry and it seems to me regardless of the u turns that should not be that case.

Larry Fine said:
Were the replacement fiber disks soaked in oil overnight before assembly?
Click to expand...
Definitely, that was 6 months ago.

Oh btw, on the last post I was not sure if my oil level was good. Now I am, after this incident I checked the oil level and it was just a bit bellow the high mark.
 
About the time of my accident in 2008, I was talking to a shop that was servicing the local cop ST1300s and the guy told me that their clutches were not lasting very long at all. And then when you add the training with the low speed maneuvers, it just adds to their quick demise.

When I was commuting, I found, due to the constant off and on the clutch I was doing, Lane Splitting, my clutches were only lasting me around 60K miles, before I had to replace them.

As for yours breaking apart like that, low oil could be a factor. But at the same time, if you are doing a lot of the low speed drills, do expect your clutches, not to last too long.
 
SupraSabre said:
About the time of my accident in 2008, I was talking to a shop that was servicing the local cop ST1300s and the guy told me that their clutches were not lasting very long at all. And then when you add the training with the low speed maneuvers, it just adds to their quick demise.

When I was commuting, I found, due to the constant off and on the clutch I was doing, Lane Splitting, my clutches were only lasting me around 60K miles, before I had to replace them.

As for yours breaking apart like that, low oil could be a factor. But at the same time, if you are doing a lot of the low speed drills, do expect your clutches, not to last too long.
Click to expand...
Thanks for that info. There is a difference, I think, between a clutch losing it's friction material too quickly and fusing too the clutch plate before shattering, within 6 months of doing the same thing. I now feel pretty convinced that there is a problem with my clutch lubrication system. Does anyone know if the clutch sits in a bath of oil or if there if something is supposed to supply the clutch with oil directly? I see at the bottom of the drain pan, on the clutch section, there is filter presumably to suck oil back in? Is there something that adds oil into the clutch area?
 
ILikeBigBikesMan said:
Thanks for that info. There is a difference, I think, between a clutch losing it's friction material too quickly and fusing too the clutch plate before shattering, within 6 months of doing the same thing. I now feel pretty convinced that there is a problem with my clutch lubrication system. Does anyone know if the clutch sits in a bath of oil or if there if something is supposed to supply the clutch with oil directly? I see at the bottom of the drain pan, on the clutch section, there is filter presumably to suck oil back in? Is there something that adds oil into the clutch area?
Click to expand...

Yeah, that would be a question for @aniwack ?
 
ILikeBigBikesMan said:
Yeah, well. I was again doing low speed u turns. I'm willing to concede that I just have poor technique if you convince me. I try to make them fairly tight and rev the engine to around 4k rmp using the clutch to control speed. I'll admit I drag that rear brake a little, perhaps too much? I only did around 20 u turns before the thing blew up. I can only imagine that the police officers when training abuse the clutch far more then that and these things are expected to handle it right? Perhaps I'm just destroying my clutch, but that friction plate is really dry and it seems to me regardless of the u turns that should not be that case.


Definitely, that was 6 months ago.

Oh btw, on the last post I was not sure if my oil level was good. Now I am, after this incident I checked the oil level and it was just a bit bellow the high mark.
Click to expand...
Yeah sounds to me like your technique doing all those u-turns burnt it up, especially the low speeds where the engine will run hotter too. Why are you using 4000 RPM? You can do these maneuvers using RPMs just a little above idle speed, maybe 1500-2000 RPM, and then only briefly. Getting that clutch so hot probably drove away the oil making them dry.

The only other shattered clutch I’ve seen on an ST1300 was from a rider who got stuck on some soft dirt or sand. He mercilessly revved and slipped the clutch trying to get out until the clutch basically left the building.

Another thought is that, sure the cops do a lot of low speed maneuvering but I doubt they do 20 u-turns, one after the other. Riding the bike between u-turns and other low speed maneuvers lets the oil circulate better and gives the clutch a rest to cool off.

I never replaced the original clutch in my ST1300 in over 150,000 miles. That included a lot of low lane splitting as well.
 
Last edited:
Not sure about the ST but most wet clutches are bath type. They also sling alot of oil around for bearings and such things. That thing is cooked...something is not fitted right... or its not in oil, if no oil i would think the cam slides would be wore as well.....I'm not sure if the valve train oil isnt supposed to return down that side of motor or not.....just thinking outloud....i would rebuild everything in myself...glad mine has 161000 on it
 
wjbertrand said:
Yeah sounds to me like your technique doing all those u-turns burnt it up, especially the low speeds where the engine will run hotter too. Why are you using 4000 RPM? You can do these maneuvers using RPMs just a little above idle speed, maybe 1500-2000 RPM, and then only briefly. Getting that clutch so hot probably drove away the oil making them dry.
Click to expand...
I do a LOT of u-turns and slow speed maneuvers for practice, think MSF BRC u-turn box. I don't count them, but 20 - 30 minutes duration, multiple days, sounds about right.
Partly to stay in practice, for real life and for teaching the BRC (even though I can't ride my ST while coaching the class.)
However, I will also add these are not high-rpm clutch slipping practice runs, either. I am slipping the clutch, but at very low rpm as mentioned above by @wjbertrand .
Sometimes 1st gear, sometimes in 2nd, but always at low rpm.
In fairness, I'll have to admit I'm barely over 30k miles (blame the GSA), but have been regularly doing these exercises since I got it at 6k miles.
For reference, how much did your last clutch cost to order?
I also wondered whether you had soaked the clutch plates in oil prior to installation, but you answered that.
 
220$ For all new friction disks, springs, gasket, 2 o rings, plus one plate which was welded to the friction disk. Yeah. I might need to not have the rpm so high, and not do them all in a row with no chance to cool.
 
wjbertrand said:
Why are you using 4000 RPM? You can do these maneuvers using RPMs just a little above idle speed, maybe 1500-2000 RPM, and then only briefly.
Click to expand...
This.
Instead of thinking about using a set (high) RPM, think about releasing the clutch enough that you can feel it start to power the rear wheel, then add just enough clutch to get the power you need for whatever you're intending to do while simultaneously adding just enough throttle to sustain the ability for the engine to provide that power. (And also to overcome the additional rear brake drag if you're using it for better stability and to control speed.)
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom