EVO: Primary Drive & Clutch

Clutch Design & Operation

The clutch system consists of the following parts, starting at the transmission and working backwards - The clutch hub & basket, the friction plates, steel plates & the spring plate, the diaphragm spring & pressure plate, the release assembly, the clutch cable and, finally, the clutch lever. The following explanation is not intended to cover every single part of the clutch system but to provide conceptual knowledge of its design and operation.

The clutch operates between the engine & the transmission. The primary chain from the engine sprocket drives the clutch outer shell unit called the “Basket”. The clutch inner shell unit is called the “Hub”. The Hub connects to and drives the transmission. Between the Basket & the Hub are the clutch plates which are actually ring-shaped with no center plate surface.

There are “Friction Plates” which have tabs (teeth as it were) only on their outside circumference that engage with the Basket. Alternating on either side of the Friction Plates are the “Steel Plates” which have tabs only on their inside circumference that engage with the Hub. The engine energy is transferred between the Friction Plates and the Steel Plates by compressing these packs of plates together (against each other) by using a Pressure Plate & Diaphragm Spring.

There is also a special Steel Plate called a Spring Plate located in the middle of the pack. The Spring Plate consists of two separate metal plates attached together with riveted movable springs. The idea is to absorb some of the instantaneous force of the clutch engagement and release it over a few microseconds of spring energy transference.

IMPORTANT NOTE: There have been problems with the clutch spring plate disintegrating. Be sure to read this section below: Spring Plate Failure

In order to operate the clutch, we need to be able to release pressure on or tightly compress these plates together using the Clutch Lever. The Clutch Release Assembly, mounted to the Pressure Plate (centered in the Diaphragm Spring), allows this control. The 'Ball & Ramp' unit converts the Clutch Cable pull, into a rotational motion, then into a direct force on the Pressure Plate (& Diaphragm Spring) to release the pressure holding the clutch plates together. In other words, when you pull the clutch lever, the cable rotates the Ball & Ramp Assy which expands itself and “pushes” out on the adjuster screw/nut, thereby, pulling the Pressure Plate away from the clutch plates. This allows separate movement of the Friction & Steel Plates - The Frictions & Steels can now rotate past each other effectively stopping the engine energy from going to the transmission.


1984Late-1990 Clutch Release - Rough Operational Diagram - Four Speed Transmission

1)

Here's the re-assembly sequence of the 1984L-1990 clutch diaphragm spring & pressure plate according to InsaneShane:

  • Here is the best way I can explain the direction (orientation) of all the parts.
  • Stack the clutch steels & frictions and install the pressure plate.
  • Then install the inner spring seat - the dome facing outward - the grooved side against the pressure plate.
  • Next install the diaphragm spring - the point of the cone facing the already installed inner spring seat.
  • Then comes the outer spring seat - the dome facing inside against the outer edge of the clutch diaphragm spring.
  • The flat thrust washer goes in next - against the grooved side of the spring seat.
  • Finally, you compress the clutch and install the retaining ring.

See this XLForum Thread - http://xlforum.net/forums/showthread.php?t=2021615

The Ball & Ramp Assembly is mounted to the inside of the Primary Cover. This necessitates the removal of the Primary Cover in order to replace either the B&R unit or the Adjuster Bearing unit.


1991-later Clutch Release - Rough Operational Diagram - Five Speed Transmission
2)

The 1994-later models have the Ball & Ramp unit mounted in a cavity of the Primary Cover (as shown above). This cavity, accessible under the 'Derby Cover', allows the replacement of the B&R unit and the Adjuster Bearing unit without removing the Primary Cover.

On the other hand, for 1991-1993 models, which also have five-speed transmissions, while the clutch operation is the same, the Ball & Ramp Assembly is mounted to the inside of the Primary Cover (as illustrated for 1984L-1990 four-speed models). This necessitates the removal of the Primary Cover in order to replace either the B&R unit or the Adjuster Bearing unit on those models.


Removing the Clutch Pack - 5-Speed

See your Factory Service Manual for the procedure of replacing the clutch plates and review the parts catalog to see all the parts involved in the assembly.

When removing the clutch pack, it is necessary to compress the Diaphragm Spring with a compression tool. There are many commercially available as well as various functional DIY versions. See the REF Section 'Clutch Hub / Spring Compressor Tools'.

It is important to understand that, once you have the Diaphragm Spring compressed, in order to remove the clutch pack snap ring (RETAINING RING - 37908-90) you will first need to press the spring seat (SPRING SEAT - 37872-90) back into the clutch hub. The L-shape of the Spring Seat is below the Retaining 'Snap' Ring and it's face is against the fingers of the Diaphragm Spring.

Once the Spring Seat is pressed inward (after compressing the spring), then, the snap ring can be pushed out of the hub fingers with light pressure toward the center of the hub. WITHOUT PRESSING THE SPRING SEAT DOWN, YOU CANNOT REMOVE THE SNAP RING.

REASSEMBLY - The Pressure Plate sits up against the clutch pack - the Diaphragm Spring sits on top of the Pressure Plate - The Locking Ring sits on top of the fingers of the Diaphragm Spring - The Snap Ring sits on top of the Locking Ring in the notches of the Hub Fingers.

CRITICAL - After compressing the Diaphragm Spring, be sure the Spring Seat (locking ring) is on top of the Diaphragm Spring fingers (not behind them). Then place the Retaining (snap) Ring in place. When releasing the compressed Diaphragm Spring, make sure the locking ring is on top of the fingers and in the proper place to keep the snap ring from coming loose.

When you compress the Diaphragm Spring, it must be compressed deep enough for the L-shaped Locking Ring to slide down the collar of the Pressure Plate far enough (to be out of the way) that the Snap Ring will go into the notches of the Hub Fingers. Then, when you release the pressure, the fingers of the Diaphragm Spring will push up (out) on the L-shaped Locking Ring until it seats (taking it's place under & inside of the Snap Ring). In this way, the Locking Ring holds the Snap Ring from coming out of place & the fingers of the Diaphragm Spring holds the Locking Ring tightly in place between the fingers & the snap ring.

clutch-springseat-lock.jpg3)

4)

Additional information threads at the XLForum.net:
http://xlforum.net/forums/showthread.php?t=1843303
http://xlforum.net/forums/showthread.php?t=2044017


Clutch Pack Stack Height

The exploding spring plate condition seems to be more prevalent in rubbermount (04+) bikes.
Although, it can and has happened with prior models equipped with the riveted spring plate.

Due to the large number of spring plate failures on 04+ models;
Many owners are replacing the spring plate with two extra steel plates and one more friction plate.
See Spring Plate Failure below.

Measuring the spring plate 5)

Typical 86-90 Sportster Wet Clutch Multiple Disc Specifications:

ITEM New Components Service Wear Limits
IN MM IN MM
Clutch Plate Thickness
Friction plate (1).150“ ± .0031”3.81mm ± .079mm .130“ (min) 3.302mm (min)
Steel plate (1).0629” ± .002“1.598mm ± .0508mm .060” 1.524mm
Clutch pack
7 friction plates
nominal midrange value
1.05“ 26.67mm N/a N/a
- service limit (total) N/a N/a 1.028” 26.111mm
5 steel plates
nominal midrange value
.3145“ 7.988mm N/a N/a
- service limit (total) N/a N/a .3045” 7.734mm
Maximum Allowable Warpage
FrictionN/aN/a .010“ .254mm
Steel plateN/aN/a .010” .254mm

Stock clutch uses 7 friction and 5 steel plates plus the spring plate.
OEM Nominal Stack Height: 1.365“ (34.671mm) + (compressed) spring plate dim.


clutch-stackheight-chart.jpg6)


Clutch Release Adjustment - Why & How

This explanation of why & how you adjust the clutch release point pulls together information from members on the XLForum.
(THIS_THREAD from member XLXR is informative)
(THIS_THREAD from member cjburr has some nice pictures of the parts discussed.)

The adjuster screw under the derby cover controls when the Ball & Ramp begins to move the pressure plate. The pressure plate must move a sufficient range for the clutch plates to move from fully engaged to fully disengaged.

Quoting XLXR - If the adjuster screw is too loose, the pressure plate will not be able to move the full distance it needs to and the clutch plates will not fully disengage causing hard shifting, hard to find neutral and clutch dragging while in gear with lever pulled in.

If the adjuster screw is too tight, the pressure plate will not move far enough to allow the clutch plates to fully engage and the clutch will slip.

In addition, if the adjuster screw is too loose, no amount of tightening the cable adjuster will compensate because the cable adjuster really does nothing except adjust the slack in the clutch cable and position of the lever. If the adjuster screw is too tight, no amount of loosing the cable adjuster will compensate. (End Quote)

Remember, the Cable Adjuster is for the Cable slack only, which sets the position of your Clutch Lever. The Clutch Release Adjuster is for the Clutch pack slack only, it sets when the Clutch begins to release. These are two different adjustments for two different functions.

Conceptual Diagram for Adjustments
clutchadjustments-diagram.jpg7)

The diagram illustrates three zones on the Clutch Lever - When fully released, Zone(1) is the 1/8” Cable Free Play where there is no tension whatsoever from the cable pulling on the lever - The lever just sorta dangles there in its mount… As you pull the Clutch Lever toward the handlebar, you reach Zone(2) which is the Adjuster Free Play - The cable is now pulling on the Ball & Ramp, rotating it to expand… This brings us to Zone(3) which occurs when the Ball & Ramp has expanded far enough to actully begin pulling the Clutch Pressure Plate away from the Clutch Pack. Zone(3) continues all the way until the Clutch Lever reaches the handlebar. If adjusted correctly, you will have these three distinct zones in the movement of your Clutch Lever and the Clutch Pack will be fully dis-engaged before the end of Zone(3) - before the lever is against the handlebars.

Zone 2 diminishes as the plates wear. The actual lever free play (Zone 1) should not change as the clutch plates wear - Here's why:

The clutch lever, once set with the cable adjuster, is in a fixed position (with a fixed length to the cable). The Ball & Ramp Assembly is mounted to the Primary Cover, so it, too, is in a fixed position. The cable (fixed length) runs between the clutch lever (fixed position) and the coupling on the Ball & Ramp Assy (fixed position).

The adjuster bearing is mounted to your pressure plate and the adjuster hex nut (around the adjuster screw) is mounted on the Ball & Ramp Assy. When the Ball & Ramp Assy is rotated, it expands the distance (ball up the ramp) between each side of itself, pushing against the Primary Cover on one side and the adjuster hex nut on the other side. This is how it pulls the clutch pressure plate away from (pushing on the adjuster screw/nut) the Clutch Pack in order to fully dis-engage the plates.

BUT, since the Ball & Ramp Assy is mounted to the Primary Cover, there is no change in the position or movement of that assembly with which the lever interacts. Therefore, Zone 1 does not change - The lever will continue to move 1/8“ before starting to tug on the Ball & Ramp coupling.

Eventually the friction zone begins to slide past the point on the clutch lever where Zone 2 meets Zone 1, and the bearing is now fully active, laterally, all the time (since the pressure plate is moving inward as the plates wear) and the Clutch Pack is slipping because the Pressure Plate can no longer fully compress the pack…
(Also see this __XLFORUM THREAD__)

MAKING THE CLUTCH RELEASE ADJUSTMENT - Refer to your FSM to be sure this procedure is correct for your particular model - Check/Adjust every 5000 miles (or as needed). Grab the Clutch Lever and squeeze and release a few times before you start - This helps to settle the position of the Release Adjuster…

Now find the Clutch Cable Adjuster - Move the boot & loosen the Jam Nut - Fully loosen the tension by screwing the two parts of the Clutch Cable Adjuster together, thus making the adjuster shorter - thereby the cable (and lever) becomes loose…

Remove the Clutch Inspection Cover (off the Primary Housing - Small Cover on '86-'93 - Large 'Derby Cover' on '94-up) (You may have to loosen or remove the left mid-mount foot peg) - be careful as you remove the cover because there is an internal spring & Release Adjuster Position Lock Nut - Remove the internal spring & Release Adjuster Position Lock Nut…

Turn the center screw of the Release Adjuster clockwise one turn away from the original position to be sure you are fully unloading any pressure - then slowly turn the Release Adjuster screw COUNTERCLOCKWISE until you feel ANY CHANGE IN TENSION - Do this a few times to be sure you feel the right spot where tension begins – When you're satisfied you have the right spot, turn the adjuster screw back clockwise 1/4 to 3/8 of a turn to be sure no preload tension is on the Diaphragm Spring.

Side note:
It may be difficult to feel the right spot while turning the screw. 8) 9)
You may want to grab the release arm and check for movement where the cable attaches.
Play (or lack of play) is obvious there as you adjust the screw.
Check for movement there, same direction as the cable operating the release.
You can easily feel the clearance change at the arm as you adjust the screw vs the vague feel you get at the screw.
The “feel” at the release arm where the clutch cable attaches is very distinct so you have a high degree of confidence you got it right.

Place the Release Adjuster Position Lock Nut back in place (turning the screw farther CLOCKWISE ONLY - JUST ENOUGH to get the nut to fit in the nearest position - Do not turn the screw more counterclockwise) - Place the spring back over the nut and place the Inspection Cover back onto the Primary Housing and retighten the foot peg if necessary…

Now, go back to the Clutch Cable Adjuster - Unscrew the two parts to lengthen the Adjuster just enough that there is still 1/8” of free play in the clutch lever movement BEFORE IT BEGINS TO ENGAGE THE CLUTCH RELEASE (check this at the cable connection to the lever) - Now tighten the Jam Nut on the cable adjuster and move the rubber boot back over it…

BEFORE STARTING THE ENGINE - TEST THAT THE CLUTCH WILL FULLY DISENGAGE - Pull the clutch lever and put the bike in second gear and roll the bike backward and forward to guarantee that the clutch is disengaging the transmission from the engine!!!

NOW PUT THE TRANSMISSION IN NEUTRAL!!!

BE EXTREMELY CAREFUL WHEN OPERATING THE BIKE AFTER MAKING A CLUTCH ADJUSTMENT - IF YOU GOT IT WRONG, THE BIKE MAY SURGE FORWARD WHEN YOU PUT IT IN GEAR EVEN THOUGH YOU HAVE THE CLUTCH LEVER PULLED FULLY AGAINST THE GRIP!!! BE SAFE - CHECK & DOUBLE CHECK!!!


Clutch Release Bearing Assembly

10)

Part Desc / Year >1986-90 1991-93 1994-2003 2004+
A- Adjustment Screw (5/16-24)11735A11735A1175211765Y
B- Bearing 8885
C- Release Plate 36730-8437918-9137918-9136731-91
D- Adjustment Screw - Retaining Ring 11046
E- Release Plate - Retaining Ring1104537909-9037909-9037909-90

The 8885 bearing dimensions are Outer OD = 30.00mm, Center ID = 10.00mm & Outer Race Width = 9.00mm

NOTE: The stock Bearing(B) and Release Plate(C) can be purchased already assembled. Part number 36731-91 is the release plate assembly, which includes both the 37918-91 release plate and the stock 8885 bearing.


Upgrade Clutch Release Bearing - HD P/N 8885 to 7200B Angular Ball Bearing

You might consider replacing the stock bearing, P/N 8885, which is a standard ball type bearing (equiv. to 6200). Using an angular contact bearing, which provides additional support in the axial direction, is a better alternative for this application. The upgraded replacement would be 7200B (not supplied by HD) and is an angular contact bearing. Thus, it is important to orient the bearing in the right direction when pressing the bearing into the Release Plate.

The wide side of the 7200B outer bearing race should be placed into the release plate first. This also means that the narrow part of the inner bearing race is first into the plate.

When correctly assembled, the narrow part of the outer race and the wide part of the inner race will each be exposed on the insertion side of the release plate. The Adjustment Screw is inserted into that wide side of the inner race, as shown below.

11)

12) 13)

Additional discussion: http://xlforum.net/forums/showthread.php?t=1688139


Clutch Basket

1986-1990 Clutch Basket Parts - Used on All Models 14)

  • 36791-84 - Clutch Shell and Sprocket
  • 36795-84 - Hub (outer) Retaining Ring
  • 36799-84 - Hub Ball Bearing
  • 36798-84 - Hub (inner) Retaining Ring
  • 36785-84 - Clutch Hub
  • 5707 - Clutch Hub Spacer
  • 11164 - Hub Bearing Retainer Ring

1991-2003 Clutch Basket Parts - Used on All Models 15)

  • 36790-91 - Clutch Shell & Sprocket
  • 37904-90 - Hub (outer) Retaining Ring
  • 36799-91 - Hub Ball Bearing
  • 37905-90 - Hub (inner) Retaining Ring
  • 36785-91 - Clutch Hub
  • 37870-91 - Spring Washer
  • 37495-91 - Main Shaft Nut

2004 and later Clutch Basket Parts - Used on All Models (except XR1200 / XR1200X) 16)

  • 36790-04 - Clutch Shell & Sprocket
  • 37904-90 - Hub (outer) Retaining Ring
  • 36799-91 - Hub Ball Bearing
  • 37905-90 - Hub (inner) Retaining Ring
  • 36785-91 - Clutch Hub
  • 37870-91 - Spring Washer
  • 37495-91 - Main Shaft Nut

XR1200 / XR1200X Clutch Basket Parts 17)

  • 37899-02A - Clutch Shell & Sprocket
  • 37891-02 - Bearing (outer) Thrust washer
  • 9214 - Hub Needle Bearings and Outer Race
  • 37892-02 - Needle Bearing Inner Race
  • 37890-02 - Bearing (inner) Thrust Washer
  • 37898-02A - Clutch Hub
  • 37870-91 - Spring Washer
  • 37495-91 - Main Shaft Nut

Stock Diaphragm Springs & Clutch Plates

1986-1990 Diaphragm Spring

  • 36792-84 - Stock Diaphragm Spring used on All Models

1991-2003 Diaphragm Spring

  • 36792-91 - Stock Diaphragm Spring used on All Models

2004-later Diaphragm Spring

  • 37910-04A - Stock Diaphragm Spring used on E04 and 05 883 Models 18) 19)
  • 37910-04B (light blue) - Stock Diaphragm Spring used on L04 and 06-up 883 Models 20) 21)
  • 37924-04 - Stock Diaphragm Spring used on E04 and 05 1200 Models 22) 23)
  • 37924-04A (purple) - Stock Diaphragm Spring used on L04 and 06-up 1200 Models 24) 25)
  • 37934-06 - Stock Diaphragm Spring used on XR-1200 / XR1200X Models 26)
    • HD Stock XR1200 Diaphragm Spring Pressure is approx. 320lbs of pressure 27)

1986-1990 Clutch Plates - Used on All Models

  • 36788-84 - 7ea - Stock Friction Plates (paper material)
  • 36787-84 - 5ea - Stock Steel Spacer Plates
  • 36789-84 - 1ea - Stock Spring Plate
    • Note: The Spring Plate is a weak point for possible failure.
      If the clutch gives you problems, it's important to check that the rivets aren't loose on the plate.
  • 36786-84 - 1ea - Stock Pressure Plate

1991-later Clutch Plates - Used on All Models (except XR-1200 / XR1200X)

  • 37911-90 - 8ea - Stock Friction Plates (paper material)
  • 37913-90 - 6ea - Stock Steel Spacer Plates
  • 37977-90 - 1ea - Stock Spring Plate
    • Note: This Spring Plate is a serious performance weakness for failure on 2004-later rubbermount models (unknown reason).
      The spring plate is often eliminated by using 2 more Stock Steel Spacer Plates and 1 more Stock Friction Plate.
  • 37912-91 - 1ea - Stock Pressure Plate

2008 and later XR Clutch Plates - Used on XR-1200 / XR1200X Models

  • 37897-02 - 1ea - Stock Friction Plate (narrow)
  • 37911-90 - 7ea - Stock Friction Plates (paper material)
  • 37913-90 - 7ea - Stock Steel Spacer Plates
  • 37895-02 - 1ea - Stock Spring Seat Damper
  • 37894-02 - 1ea - Stock Rear Clutch Spring
  • 37896-02 - 1ea - Stock Pressure Plate
91-up clutch plates and spacing (F-St-F-St-F-St-F-SP-F-St-F-St-F-St-F). 28)

Upgrade Clutch Diaphragm Springs - Pressure

Below are a list of upgrade versions. The 'xx% stronger' are claimed values by the respective vendors. Energy One suggests that if you are using a diaphragm spring of +25% that you should also upgrade your pressure plate to a billet version because they have had issues with the stock cast pressure plate cracking. 29)

L1984-90 Sportster

Barnett Scorpion Clutch Kit 607-30-10084 30)

  • MT-33-6 - - - 396lbs (six springs)
  • MT-112-6 - - 420lbs (six springs)
  • MT-113-6 - - 480lbs (six springs)

1991-later Sportsters

Screamin’ Eagle HD-style Clutch Spring 31)

  • 350lbs - 10% Stronger Than Stock 1200 Clutch Spring (SE Clutch Spring 37949-98A)

Energy One HD-style Clutch Spring 32)

  • 340lbs - 15% Stronger Than Stock 1200 Clutch Spring (BT15) (% based on '91-'03 1200 OEM spring)
  • 380lbs - 25% Stronger Than Stock 1200 Clutch Spring (BT25) (% based on '91-'03 1200 OEM spring)

Barnett HD-style Clutch Spring 33)

  • 360lbs MT-81 - 10% Stronger Than Stock 1200 Clutch Spring (502-00-01081)
  • 400lbs MT-77 - 25% Stronger Than Stock 1200 Clutch Spring (502-00-01077)

Barnett Scorpion Clutch Kit 607-30-10091 34)

  • MT-18-6 - - - 348lbs (six springs)
  • MT-112-6 - - 420lbs (six springs)
  • MT-113-6 - - 480lbs (six springs)

These springs can be mixed such as: 35)

  • 3x MT-18 plus 3x MT-112 = 384 lbs
  • 3x MT-18 plus 3x MT-113 = 414 lbs
  • 3x MT-112 plus 3x MT-113 = 450 lbs


Screamin' Eagle® Performance Clutch Kit

HD has a Performance Clutch Kit (Number 38002-04) designed to fit 1991 and later XL and 1994 to 1997 1340 Evolution® model motorcycles.36) This kit is still being sold by HD as of 12-22-2016.

  • The nine high performance friction discs and eight spacer discs in this kit replace the original eight paper friction discs and six spacer discs. This kit also replaces the spring plate and diaphragm spring with a higher rate diaphragm spring.37)
  • Cautions: Do not reinstall the OE spring plate and diaphragm spring with this kit. Doing so will affect the stacked height of the clutch discs. The spacer discs supplied in this kit must be used with the high performance friction discs. Do not use the original equipment (OE) spacer discs with this kit. Doing so will affect the stacked height of the clutch discs, resulting in clutch slippage.
  • Installation, refer to the applicable Harley-Davidson Service Manual for installation of friction discs, spacer discs, and diaphragm spring in kit, but follow these important guidelines:
    • Remove the original eight friction discs, six spacer discs, spring plate, and diaphragm spring from the clutch assembly as described in the Service Manual, and discard.
    • Replace with nine high performance friction discs, eight spacer discs, and diaphragm spring from kit. Place a friction disc into the clutch shell first, then alternate spacer discs and friction discs.
    • Kit includes:
      • Disc set including 9 friction and 8 spacer discs. Part #(38001-04)
      • 1 Spring, clutch diaphragm Part #(37949-98A)



Spring Plate Failure

As mentioned above, the Spring Plate is located in the middle of the clutch pack. It consists of two separate steel plates attached together with riveted, movable, flat springs sandwiched between the two steel plates. There is a friction plate on either side of the Spring Plate. The idea is to absorb some of the instantaneous force of the clutch engagement and release it over a few microseconds of spring energy transference. See this Post#44

While the functional goal is a good idea, this Spring Plate has caused untold headaches for many riders. When the rivets fail they get caught in between the friction & steel plates, causing the clutch to malfunction, damaging the plates & the clutch basket. 38)

Here's a good description of the most common symptoms when the Spring Plate Fails:

I noticed the clutch felt like it was dragging then it became harder to get neutral gear and when I stopped I could see that the cable had some slack to it and the lever didn't engage until halfway into the pull towards the grip. It got harder to deal with so I stopped and borrowed 2 cresent wrench's and took the slack out where the adjuster deal is on the cable where it runs down the frame tube.

I thought that would be fine at least to get me home and it did help a little but it quickly became just as big a problem as it was before I adjusted the cable. (Quoted from FrankZ of the XLForum. 39))

Parrothead, in the same thread, mentions that, like others, when his Spring Plate failed he noticed a gold shimmer (brass flecs) in the primary oil when servicing the engine. This is a tell-tale sign that can be observed even before opening the primary cover to examine the condition of the clutch basket & primary cavity.

If the failure is not caught in time, even sheered rivets may be found in the primary oil when draining it for repairs.

This problem is best addressed before it happens. This XLForum Thread includes an ad hoc poll of those who have or have not had failures of their Spring Plate. Currently, the poll shows the following results: Solid – No=61 Yes=19 / Rubber - No=95 Yes=67 – which shows the rubbermount models (2004-later) failing at double the rate of the frame mount models (1986-2003).

Since the poll is not a controlled study, I'm sure it is not accurate. In fact, I suspect the failure rate difference between the models is higher than reflected with the rubbermounts failing much more often than the frame mount models. In any case, the Spring Plate does fail on either model EVO Sportster and the damage is sufficient to make this an important problem to avoid.

Replacing the old Spring Plate with a new, stock Spring Plate is not a typical solution advocated on the XLForum, although it is an available one. Why replace a failure prone part with another of similar weakness?

The preferred choice is to eliminate the Spring Plate entirely by installing two extra steel plates & one extra friction plate. This works for 91 and up clutches. It is possible to accomplish on 86-90 models but due to the thicker friction plates in them, it will not work unless you have enough wear on your plates to get the total stack height down below 1.5662“. 40) While it is possible to do so on 91 and up models with stock plates, a more typical implementation for 86 and up models is using a complete aftermarket kit of new steel plates & friction plates. There are a number of suppliers of such kits, such as, Energy One, Barnett & Alto, in a number of different materials.

This solution does make the clutch engagement a bit more 'grabby' and there is sometimes an associated 'squeel'. But most users prefer the peace-of-mind of eliminating the Spring Plate despite these 'drawbacks'.

Some power shifting users take this opportunity to replace the stock Diaphragm Spring with one that is stronger. Others try to avoid making the clutch lever pull harder and may even install clutch release kits that ease the clutch lever pull.

If you have an actual failure of the Spring Plate, with missing rivets having been strewn around the primary cavity, be sure to check everywhere those bits may have gone. The clutch basket may have been scored by the failure which will require careful filing to remove any burrs or, if bad enough, may require replacing the clutch basket. If not properly repaired, the new plates will not move smoothly to release the clutch engagement.

Also, the existing clutch plates (either steels or frictions) may have been warped during the failure. If the Spring Plate disintegrated, it is best to replace all the steels & frictions to avoild carrying damaged parts foward to damage new parts. You should also carefully check that the Pressure Plate & Release Plate have not been damaged, nor any other primary components (chain, sprockets, etc).

Here are images of the carnage resulting from the Spring Plate Failure:
41)42)43)


NOTE: Alto has released an upgraded Spring Plate design for the '91-later Sportsters - Alto P/N 095763HD. It utilizes Stainless Steel rivets instead of the previous Brass Rivets design. Time will tell if this is more reliable.44) >>>Link To Alto PDF<<<



You may also want to explore these pages in the REFerence section:
'91-later Alternative Clutch Pack Using XR1200 Parts
'91-later Aftermarket Clutch Packs


gototechnicalmenu.jpg


1) , 2) , 7)
Illustration created by IXL2Relax at the XLForum
3)
Annotations created by IXL2Relax at the XLForum
4)
Image from jigoe007 from http://xlforum.net/forums/showthread.php?t=2044017 Annotations created by IXL2Relax at the XLForum
5) , 28)
photos by Hippysmack
6) , 10) , 13)
Annotated by IXL2Relax at the XLForum
9)
thanks to Jollly Rogers for the suggestion http://xlforum.net/forums/showthread.php?p=5761695#post5761695
11)
Pics by goblin_dust at this thread: http://xlforum.net/forums/showthread.php?t=1987885 - Annotated by IXL2Relax at the XLForum
12)
Thanks to Reddtigger - xlforum.net/forums/showthread.php?t=1688139
14)
86-90 HD Sportster Parts Catalogs
15)
91-03 HD Sportster Parts Catalogs
16)
04 and up HD Sportster Parts Catalogs
17)
09 and up HD Sportster Parts Catalogs
18) , 22)
2004 HD Sportster FSM 99451-04 pg 39
19) , 23)
2005 HD Sportster FSM 99451-05A pg 41
20) , 24)
2004 HD Sportster FSM 99451-04A pg 41
21) , 25)
2006 HD Sportster FSM 99451-06 pg 41
26)
2009 HD Sportster FSM 99451-09A pg 59
36)
shanneba from the XLFORUM
38)
Image to the right by WestJC7745 - xlforum.net/forums/showthread.php?t=1698620
39)
xlforum.net/forums/showthread.php?t=2070923
41)
Image by jbyun - xlforum.net/forums/showthread.php?t=49915
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Image by vferdman - xlforum.net/forums/showthread.php?t=49915
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Image by xlxr - xlforum.net/forums/showthread.php?t=302142
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