I preparation to pull apart my motor, I wanted to find out some information on removing the STM Slipper Clutch.
I was already aware that there was a special STM tool needed, and these appear to be likes hens teeth. And any information on the removal of these also seems to be really hard to find.
In the end, I spoke to Millar, who had made his own custom STM tool from a Mountain Bike Bottom Bracket Removal tool, which he kindly sent me.
And so I begun.
Firstly, here is the diagram from STM, which is about as good as their instructions get.
![Image]()
Here are the tools you’ll need.
Ideally the STM tool
![Image]()
But as most can’t find/afford this tool at over £100, we’ll go with these…
Motion Pro Clutch Holding Tool
32mm Socket
27mm Socket
Suitable Breaker Bar
Millar’s Custom STM removal Tool (MCRT)
4mm Allen Key
Grease
Loctite
![Image]()
Right… onto the removal.
Firstly Undo the 6x 4mm Allen Keys holding on the red pressure plate spider (should all be red, but mine has made contact with the outer casing in the past) to reveal the 32mm internal Hex (spring stopper hub) and the inner hub nut.
![Image]()
![Image]()
Hold the pressure plate with the clutch holding tool, I found using the sprocket holders a lot easier to get purchase. Insert the MCRT into the clutch and undo the internal hex, whilst holding the clutch holding tool.
![Image]()
![Image]()
Once removed you should see the bearing and the stepped spring stopper plate, simply lift this off.
![Image]()
This will reveal the primary spring, which again is simply lifted off, followed by the pressure plate and the clutch pack.
![Image]()
![Image]()
Leaving you with this in the engine and this on the bench
![Image]()
![Image]()
Then the hub nut needs to be removed, 27mm, What I did was to remove two of the rotation limiting pins from opposite sides and hold then hold the drum with the sprocket holders on the cluth holding tool, and then undid the nut.
![Image]()
![Image]()
![Image]()
From then, the rest of the clutch assembly, Secondary Spring, Drum, Hub etc, can all just be lifted off as one, and the clutch is removed from the engine. Job Done!
If it was just a removal and re-fit you were after then stop here, and when it is time, work backwards from this point
If spring pressure needs to be changed, to help with setup, then continue to work on the assembly.
Undo all 6 x 4mm allen bolts on the drum stopper hub, and remove it. This gives access to the secondary spring.
![Image]()
![Image]()
Adjust the spings as you feel is needed at this point.
Now for some general maintenance before you rebuild.
Remove the secondary spring support and the drum to reveal the 6 balls on their ramps.
![Image]()
![Image]()
Re-grease the base of the ramps and reinstall the 6 balls.
![Image]()
![Image]()
Re-install the drum and secondary spring support followed by the secondary spring.
![Image]()
![Image]()
Now, place the drum stopper hub back in the assembly and be ready to install the allen heads with loctite.
I installed 3 of the 6 first, making sure the spring was uniformly compressed by doing each up bit by bit.
![Image]()
Then I installed the other 3 allen bolts with loctite
![Image]()
I then lightly greased the outside of the drum and installed the pins.
![Image]()
![Image]()
At this point you can return to installing the clutch pack and pressure plate, in the reverse order of disassembly.
HTH
Also available in PDF format if anyone wants it, just PM me
Cheers
Grant
I was already aware that there was a special STM tool needed, and these appear to be likes hens teeth. And any information on the removal of these also seems to be really hard to find.
In the end, I spoke to Millar, who had made his own custom STM tool from a Mountain Bike Bottom Bracket Removal tool, which he kindly sent me.
And so I begun.
Firstly, here is the diagram from STM, which is about as good as their instructions get.
Here are the tools you’ll need.
Ideally the STM tool
But as most can’t find/afford this tool at over £100, we’ll go with these…
Motion Pro Clutch Holding Tool
32mm Socket
27mm Socket
Suitable Breaker Bar
Millar’s Custom STM removal Tool (MCRT)
4mm Allen Key
Grease
Loctite
Right… onto the removal.
Firstly Undo the 6x 4mm Allen Keys holding on the red pressure plate spider (should all be red, but mine has made contact with the outer casing in the past) to reveal the 32mm internal Hex (spring stopper hub) and the inner hub nut.
Hold the pressure plate with the clutch holding tool, I found using the sprocket holders a lot easier to get purchase. Insert the MCRT into the clutch and undo the internal hex, whilst holding the clutch holding tool.
Once removed you should see the bearing and the stepped spring stopper plate, simply lift this off.
This will reveal the primary spring, which again is simply lifted off, followed by the pressure plate and the clutch pack.
Leaving you with this in the engine and this on the bench
Then the hub nut needs to be removed, 27mm, What I did was to remove two of the rotation limiting pins from opposite sides and hold then hold the drum with the sprocket holders on the cluth holding tool, and then undid the nut.
From then, the rest of the clutch assembly, Secondary Spring, Drum, Hub etc, can all just be lifted off as one, and the clutch is removed from the engine. Job Done!
If it was just a removal and re-fit you were after then stop here, and when it is time, work backwards from this point
If spring pressure needs to be changed, to help with setup, then continue to work on the assembly.
Undo all 6 x 4mm allen bolts on the drum stopper hub, and remove it. This gives access to the secondary spring.
Adjust the spings as you feel is needed at this point.
Now for some general maintenance before you rebuild.
Remove the secondary spring support and the drum to reveal the 6 balls on their ramps.
Re-grease the base of the ramps and reinstall the 6 balls.
Re-install the drum and secondary spring support followed by the secondary spring.
Now, place the drum stopper hub back in the assembly and be ready to install the allen heads with loctite.
I installed 3 of the 6 first, making sure the spring was uniformly compressed by doing each up bit by bit.
Then I installed the other 3 allen bolts with loctite
I then lightly greased the outside of the drum and installed the pins.
At this point you can return to installing the clutch pack and pressure plate, in the reverse order of disassembly.
HTH
Also available in PDF format if anyone wants it, just PM me
Cheers
Grant
