The XR1200 Clutch
 
 
The XR1200 makes use of the clutch assembly formerly found on the XB Buells.  It is similar in its external dimensions to the XL clutch assemblies, and, with some modification during installation it is said to be possible to retrofit a XL clutch into an XR.  The XR/XB clutch design does have some improvements over the regular Sportster clutch.
 
Several of the clutch parts, including the full fiber and steel plates, are interchangeable with an XL clutch - but the clutch shell, hub, pressure plate, bearing, etc. are different.The XR/XB clutch has an internal compensating mechanism to reduce drivetrain shock under hard launches and sudden downshifts.  It also incorporates a "judder" spring to reduce chatter when the clutch lever is released. 
 
 
Below is a picture of the complete clutch assembly, after it has been removed from the primary case.  It is comprised of two main parts:
  • the outer clutch shell with the starter ring and drive gear for the primary chain, and
  • the inner clutch hub with the fiber and steel clutch plates, pressure plate, and diaphragm spring

 

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Complete Clutch Assembly

 
The below is a side view of the clutch assembly.
 
The center clutch Adjustment Screw and Release Plate must be removed to unscrew the nut on the main shaft to remove the clutch assembly from the primary.  But, this shaft needs to be back in place to disassemble the clutch pack.
 

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Clutch Alt View

 
The below picture shows the gap between the outer diaphragm spring and the back of the pressure plate.  (These are the openings between the eight standoffs that hold the outer retaining ring that keeps the clutch pack together.)  Nominally, this gap is about X/Y" wide.  This allows the Ball and Ramp assembly, activated by the clutch lever and cable, to pull the Pressure Plate outward about 1/8" and let the friction and steel plates spin freely to disengage the engine from the drivetrain.
 
In my clutch, the seat ring that helps keep the clutch pack retaining ring in place had broken, and part of it had wrapped under the diaphragm spring restricting the movement of the diaphragm spring and pressure plate.  This was causing the clutch to constantly drag when the clutch lever was pressed.  Hence, the eagle-eyed may notice that I had actually already removed the broken retaining ring seat in these pictures, and temporarily re-assembled the clutch pack.
 
 

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Diaphragm Spring Movement Range
 

Before the clutch diaphragm spring is removed, the clutch pack can be lifted out of the outer clutch shell as a unit to inspect the clutch shell.  (In Big Twin and XL Sportster clutch assemblies, the center hub is pressed into the center bearing in the clutch shell.)  The XR/XB design makes it easier to install slipper clutches and other clutch pack mods.
 

Here is a look at the inside of the front of the clutch shell.
 

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Clutch Shell - Front
 

Andbelow is what the back of the clutch shell looks like. 
 
Notice the six recesses that house the springs which buffer the compensating mechanism in the XR's clutch shell.  The clutch housing consists of two pieces which are riveted together and will wind up slightly during accel/decel.  They are buffered by the compensating springs to take some of the shock out of the drivetrain.
 

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Clutch Shell Back
 

The next two pictures show a couple of the compensating springs in their housings.  These springs have been known to break under heavy use but, in good condition some of them will be loose or move when the clutch is disassembled.  They are different lengths in order to engage at different points and soften the shock of sudden engine accel/decel on the drivetrain.
 

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Clutch Shell Compensating Spring

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Clutch Shell Compensating Spring - Alt
 

Separately, here is the inner clutch pack removed from the outer clutch shell, with the diaphragm sping and its retaining ring still holding the pack together.
 
 

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Clutch Pack
 

To disassemble the clutch pack, it is placed back in the outer clutch shell to keep plates aligned as the spring compressor tool is used to release the retaining ring on the diaphragm spring.  One needs a spring compressor tool to compress the diaphragm spring and take the pressure off of the retaining ring, so that the ring holding the diaphragm sping in place can be removed.
 
 
The first step to installing the tool is to thread its center shaft on to the clutch Adjustment Screw.
 

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Clutch Pack Spring Compressor - Install
 

With the center threaded part installed, the outer ring and support bearing are set in place, and the handle threaded on.  Then the center shaft is held in place with an open end wrench while the handle is turned - compressing the diaphragm spring to release the tension on the retaining ring. 
 
The diaphragm spring should only be compressed enough to release the pressure on the retaining ring.  CAUTION:  Over-tightening can damage the diaphragm spring and clutch pack.
 

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Clutch Spring Compressor
 

With the diaphragm spring pressure removed, the retaining ring (and the seat which would be installed under it) can be removed from the grooves in the fingers of the clutch hub.  A screwdriver may be needed to help lift the retaining ring out of the grooves in the clutch hub to remove it.
 

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Removing the Retaining Ring
 

The below picture shows the diaphragm spring retaining ring, and its seat ring.  The seat should be a continuous ring - mine had cracked in one spot, and was no longer staying properly in place on top of the diaphragm spring.  It was actually restricting movement of the diaphragm spring and the pressure plate, and causing my clutch to drag badly.  (I had pulled the seat off earlier in the day, when I was examining how it broke, and hence it is not shown in the preceding pictures.)
 

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Retaining Ring and Seat
 

With the retaining ring removed, I pulled the clutch pack back out of the clutch shell and removed the stack of parts - starting with the diaphragm spring.
 
This is the 400 lb Barnett MT-77 diaphragm spring.  A better choice for most XR1200 builds would be the 360 lb Barnett MT-81 spring or the 350 lb spring in the SE Performance Clutch Kit.  The MT-77 is a very stiff spring at the clutch lever!
 

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Diaphragm Spring
 

Next off is the clutch pressure plate.  With it lifted off, the stack of fiber friction and smooth steel clutch plates is exposed.
 

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Pressure Plate
 

There are seven full sized friction plates (37911-90) in theXR1200 plate stack.  These are alternately interlaced with the smooth steel plates.  The friction plates are notched on their outer edge and engage the clutch shell.  The XR parts manual describes the friction material as "paper."
 

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Full Fiber Plate
 

This friction plate has about 20,000 miles on it.  The friction material may look thin, but if you take a look at a new plate (
click here to see a new SE friction plate), it actually has a good amount of material left. 


The stock plates have friction material placed on it in individual tabs.  The SE plates have a continuous ring of friction material with a waffle print pressed into them.

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Edge of Fiber Plate
 

There are also seven steel plates (37913-90) in the clutch pack.  These are notched on their inner side to engage the clutch hub.  With the diaphragm spring released exerting force on the pressure plate, the stack is clamped together and the engine can drive the transmission.
 

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Steel Plate
 

The eighth, and bottom, friction plate in the XR1200 clutch pack is a narrow plate.  This plate has a concave judder spring installed in its center and is supposed to help reduce chatter when the clutch is released.  This narrow friction plate is not found in the SE Performance Clutch Kit, and would need to be separately purchased if the SE kit is used for the full plates.
 
 

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Narrow Fiber Plate

 
Below is a picture of the concave judder spring.
 

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Clutch "Judder" Spring
 


And the judder spring in the center of the narrow fiber plate, where it would be when installed on the clutch hub...


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Judder Spring with narrow Plate
 

The last part in the clutch plate stack is the seat for the damper, or "judder" spring, that goes against the clutch hub.  The judder spring will spin on this seat as the clutch initially engages to help reduce vibration as the clutch lever is released.

 

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Damper Spring Seat
 


Conclusion
 
 
I pulled the clutch from my XR because it was dragging and I feared the clutch shell might have been damaged, or steel clutch plates had warped.  As it was, the problem was simply a broken seat for the diaphragm retaining spring.  The fix was easy, but removing the clutch this time gave me a chance to snap these pictures - and to attempt to install the AIM-Tamachi Variable Pressure Clutch mechanism.  Although it was not possible to use the AIM VPC in the XR,  I have documented the attempt at installation here.
 
In my opinion, the basic XR clutch design is very good.  The stock friction plates are adequate for most applications, and for increased power in mildly "built" XR motors.  What some riders may wish to do however, is upgrade to a stronger diaphragm spring.   But of course, clutch upgrades and slipper clutch assemblies are all available....
 
 
For a look at some XR clutch upgrade options, click here.
 

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