Installing the VPC on the Clutch Pack
 
 


The XR1200 uses the Buell style clutch hub, and not the clutch hub which is common to the rest of the Sportster family for which the VPC was designed.  The fingers of the XR1200/Buell clutch hub, which hold the diaphragm spring retaining ring, are wider on the XR1200 clutch hub than on the standard Sportster clutch hub.  This creates a problem with interference between the centrifugal weights of the VPC, and the retaining ring mounting fingers of the clutch hub - which prevents the retaining ring from being installed when the diaphram spring is compressed.  Installation of the VPC on the XR1200 clutch hub is similar to installation on other Sportsters.  However, there is an additional machining step required during installation because of the interference problem with the Buell-style clutch pack which the XR1200 uses.  
NOTE:  Although it is possible to install the VPC on the XR1200-Buell clutch hub, it is not possible to use the VPC in the XR1200 because of clearance problems with the primary case cover.  Substantial modification to the primary cover, requiring re-posiitioning of the left-side driver's footpeg and the shift lever, would also be required to install the VPC on the XR1200.  This prevents the XR1200 from being used on the XR1200 without a great deal of additional fabrication.  The below information is therefore academic, because while the VPC can be installed on the clutch pack, other factors will prevent use on the XR1200.

Here are some notes on installation of the VPC on the XR1200 clutch pack.
 
The VPC
 
 
As mentioned, the VPC comes neatly packaged with instructions and a  longer adjustment screw and spacer for the Ball and Ramp assembly.  The longer adjustment screw provides clearance between the the Ball and Ramp assembly of the Sportster clutch, and the VPC's centrifugal weights.
 
 

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VPC in Package
 

The VPC also comes with the proper weight spring for your application.  Choices range from a 190 lb plate with a very light initial clutch lever feel, through a heavy duty 240 lb spring for larger cube high TQ motors that will have a light clutch lever and a strong clamping force.
 
 
While the 240 lb VPC spring has a lighter feel at idle and around town, the centrifugal weights increase the clutch the clamping force significantly higher than other heaviesr springs as engine rpm increases.  The force increases with rpm as shown  in the following:
     240 lbs     at     1000 RPM
     300 lbs     at     3000 RPM
     350 lbs     at     4000 RPM
     500 lbs     at     6000 RPM
The weight of a stock diaphragm spring, for comparison, is 320 lbs
 
The following picture shows the 240 lb spring which I selected (on right) compared to the Barnett 400 lb plate (on left).  .
 

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Diaphragm Spring Comparison
 

The next picture shows the VPC diaphragm spring in place on the pressure plate of the clutch pack.
 

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New Diaphragm Spring in Place
 

Here is the VPC set in place on the diaphragm spring and clutch pack.


Note that the seat for the retaining ring that holds the clutch pack together, which is its own separate piece in an unmodified clutch, is part of the VPC assembly.  With the diaphragm spring retaining ring installed, It is used to mount the VPC on the clutch pack.

To install the VPC, there needs to be clearance between the centrifugal weights and the mounting fingers so that the retaining ring seat can drop down low enough to install the retaining ring when the diaphragm spring is compressed.


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VPC set in Place
 


Before attaching the HD spring tool to install the retaining ring, the stock adjuster screw needs to be replaced with a slightly longer AIM provided screw. 

This will increase the clearance to the Ball and Ramp release assembly to accommodate the VPC centrifugal weights.


 

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Original adjuster screw



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Adjuster Screw removed

 
 
 
 
 
 
 
 
The adjuster screw is held in pace with a snap ring, as shown in the picture to the right.
 
 
 
 
 
 
 
 

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Old and New Adjuster Screw

 
 
 
 
 
 
 
 
 
This shows the slightly longer AIM adjuster screw on the right vs the stock adjuster screw on the left.
 
 
 
 
 
 
 
 
 
 
Here is the longer AIM adjuster screw installed, and ready to be put in the clutch pack to attach the HD spring tool to, and compress the diaphragm spring to insert its retaining ring.







The below picture shows the new screw installed in the bearing plate..



 

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New Adjuster Screw
 


Clutch Hub Modification Required for the XR1200
 
 
As noted above, the XR1200 uses the Buell style clutch pack, and not the clutch hub which is common to the rest of the Sportster family for which this VPC was designed.  The fingers of the clutch hub which hold the diaphragm spring retaining ring are wider on the XR1200 clutch hub than on the standard Sportster clutch hub.  This creates a problem with interference between the centrifugal weights of the VPC, and the retaining ring mounting fingers of the clutch hub which prevents the retaining ring from being installed when the diaphragm spring is compressed.
 
The following picture shows the VPC in place, and one can see that the centrifugal weights are over the top of the retaining ring fingers.  As mentioned above, on a stock clutch the seat for the retaining ring is a separate piece and there is no problem here.  But, the VPC incorporates the seat for the retaining ring as part of the VPC assembly to hold the VPC in place.  There needs to be clearance between the centrifugal weights and the mounting fingers so that the retaining ring seat can drop down low enough to install the retaining ring, when the diaphragm spring is compressed.

The problem with interference can be relatively easily fixed by machining the outer edge of the fingers, to allow the centrifugal weights to drop into place during installation.


 

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Interference

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Interference Close Up

 
 
 
 
 
 
 
 
To the right is a closer look at the centrifugal weights touching the retaining ring mounting fingers of the clutch hub.
 
 
 
 




 
And below, one can see the shape of the fingers on the clutch hub, before machining.  (For the eagle-eyed, The grinding in the pressure plate below is from where I initially tried removing a bit of material from the surface of the pressure plate to let the diaphragm spring collapse a bit more, before I realized the interference problem with the weights.  The pressure plate should not need to be touched.)
 
 

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Fingers - before

 
To gain the needed clearance, the outer corners of the clutch hub fingers need to have a curved notch cut into them.  This follows the shape of the centrifugal weights and provides needed clearance for assembly.
 

The pictures below show a slightly closer look at the clearanced outer edges of the clutch hub fingers.  In these pictures the machining is not quite done.  I used a 0.25" round sanding drum for final material removal and radiusing of the cuts.

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Fingers After

 




















 
 
 


 
 
 

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Fingers After Machining - again


The width of the fingers before modification is about 0.320".  The remaining flat surface on the top of the fingers will be 0.14" when the cuts are done.  The depth of the cuts is 0.18" inward and about the same depth, to provide a notch into which the centrifugal weights can drop during installation of the VPC.


The Clutch Spring Tool and Final Assembly
 
 
With the fingers of the clutch hub machined, I put the clutch pack back together and set the VPC in place.  Next, the HD clutch spring tool is attached to the adjuster screw and the handle is turned to compress the clutch diaphragm spring.
 
Now, with the diaphragm spring compressed, the centrifugal weights will not stop at the top surface of the mounting fingers, and the retaining ring seat that is part of the VPC will drop low enough to install the retaining ring.  (You can see this slot in the sides of the clutch hub fingers in the center of the clutch pack.)
 

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Assembling Pack

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Everything Fitting

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Just one more picture showing the little bit of clearance that is now between the centrifugal weights and the mounting fingers, once the machining is done and the clutch spring is compressed.
 
 
 
 
 
 
 
 

 
And below, here is what it looks like with the retaining ring installed. (The ring can be maneuvered easily into its place by using two small flat bladed screw drivers to guide it into its slot, by levering against the centrifugal weights.)   I am lifting the center weight to show the shape of the radiused cut.  The left and right weights show the clearance between the centrifugal weights and the clutch hub fingers, once the installation tool is removed.
 

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Retaining Ring in Recess
 


And here is the VPC fully installed on the clutch pack.
 

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VPC on Clutch Pack - Assembly Complete
 


Conclusion
 
 
Overall, installation of the VPC on the XR1200 clutch pack is not difficult for someone with the proper tools, and some decent mechanical skills.  It takes some machining of the clutch hub fingers, but the assembly is clean and the VPC does look pretty impressive when mounted on the XR1200 clutch assembly.
 
But again, while the VPC can be installed on the XR clutch pack, the VPC will not work within the XR1200 primary case.  The XR's clutch cable entry point interferes with the VPC centrifugal weights.  So, the VPC is a nice idea, but not for the XR1200 unless heavily modified.
 
 
 

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