XR1200 Rear Motor Mount Upgrade

While the XR1200 may be the best handling motorcycle that Harley Davidson has made recently, there are still several aftermarket upgrades to improve its suspension and handling.  Shock absorber and front fork upgrades are common among XR riders.  Until a while ago I had overlooked one of the most dramatic and cost effective handling upgrades that can be made to the XR1200 – installing solid rear motor mount/swing arm bushings.

During a couple of days running the XR through Keith Code’s California Superbike School (CSS) at Virginia International Raceway (VIR), I talked with one of the CSS instructors who races XR1200’s about specific things to improve my track speed and cornering.  He was convinced that upgrading the XR1200 suspension with solid motor mount/swing arm bushings was a necessity for cornering.  I wasn’t sure what kind of change the bushing upgrade would make, but I figured I would give it a try.  I ordered the polypropylene bushings from Vance & Hines a week later, they showed up that later that week, and I slipped them in the bike over the weekend  because I was planning an open track day at Summit Point Raceway in West Virginia the following Monday.  That gave me the chance to compare two days of riding VIR on the XR1200 followed by a day at Summit Point, to compare just the effect of the bushing upgrade on the suspension/handling.


The Vance & Hines Polypropylene Rear Motor Mounts

Although the XR1200 swing arm is unique to the XR1200, the XR shares the same swing arm mounting design and hollow rubber motor mount bushings  -  or in the Harley vernacular – “Isolator, rear mount" ( 48492-04), with other late model Sportsters.  The bushings hold the rear of the engine in the frame, while letting it float around a pivot shaft to damp engine vibration. The swing arm - or “Rear Fork" (47674-08A in silver) - mounts to the rear of the engine on the same pivot shaft  - or “Shaft, swing arm pivot" (41568-04).  This solidly mounts the swing arm to the rear of the engine, while allowing the whole engine and swing arm combination to vibrate and twist within the XR1200’s frame.

With the OEM rear motor mount  bushings the swing arm moves with the vibrating engine, and can twist in the frame as the bike is thrown into corners.  The fix for this is to replace the hollow OEM rubber engine mount bushings with solid bushings.  As a part of its upgrade kit for the XR1200 race series, Vance & Hines sells solid polypropylene engine mount bushings to upgrade the XR1200 suspension.  This lets the XR1200 turn much more precisely, and hold a straighter line at speed more easily. The V&H polypropylene motor mount bushings  -  “Polypropylene Rear Motor Mount" (35-0260)  -  are a direct bolt-in replacement for the XR1200’s hollow OEM rubber engine mount bushings.

Below is a picture of the front and back of a pair of the Vance & Hines polypropylene motor mount bushings.  Vance & Hines sells them individually, but two are obviously needed to upgrade the XR1200 – one for each side of the swing arm.  They are well manufactured and machined to fit precisely in the XR1200 (or other 2004 model year and later Sportster).



Figure 1
Figure 1 - Vance & Hines Polypropylene Motor Mount Bushings for the XR1200
 


Installation of the V&H polypropylene bushings is straight forward and shouldn’t be a problem for a rider with good mechanical skills and the ability to follow directions.  Installation requires removing the exhaust system, transmission pulley cover, drive belt, belt tensioner pulley, and rider’s foot pegs with the rear brake and shifter controls. 

AND - I wouldn’t have wanted to try this upgrade without an air impact wrench.  (The swing arm bolts fasten to a pivot shaft that passes through the back of the engine, and these mounting bolts can be tough to remove without one.  This is because the centRal pivot shaft is held in place by a lockplate that has locator tabs to keep from rotating.  These tabs are easy to break loose from their recesses with too much torque - and then the pivot shaft will spin freely making it difficult to remove the end bolts.) 

The two front, and one rear, engine locating links also need to be unfastened so that the engine can be rocked slightly to the side to remove/install the swing arm bushings.



After disassembly, the OEM bushings take a bit of finessing to get out of their mounting points, but will come out by moving the rear of the engine left or right a bit and pushing the bushings out of their mounting spots.  The new V&H polypropylene bushings are then installed, and the bike is reassembled.

Installation time will vary depending upon the skills of the installer, but can be done easily in a couple of hour
s.




Removing the OEM Motor Mount Bushings
 

Here is my 2009 XR1200 ready for installation of the new Vance & Hines polypropylene motor mount bushings.  It still carries its number from CSS at VIR and has the mirrors and lenses taped.  I’ll leave it that way through the coming track day at Summit Point.



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Figure 2 - 2009 XR1200 Ready to start install
 

On the right side of the XR1200, everything blocking the swing arm pivot bolts needs to be removed.  The rear half of my V&H exhaust will come off, along with the transmission pulley cover, rider’s footpeg and rear brake lever, the tensioner pulley for the drive belt, and the drive belt.


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Figure 3 - Close up of the XR1200 Right Side



I did a bit of the prep before slipping the lift under the bike.  The belt tensioner or “idler” pulley still needs to come off, but the swing arm pivot bolt is now accessible.  Removing the two nuts on the idler pulley mounting bracket (seen at the lower left edge of the transmission pulley) will let the idler bracket come off and gain clearance to move the engine to work on the right side motor mount bushing.

 

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Figure 4 - Right Side Miscellany Removed



Next the left side.  I have a Storz shifter installed, otherwise the stock shift linkage needs to be removed with the left side footpeg.


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Figure 5 - Left Side, Driver's Foot peg



With the left driver’s footpeg removed, the left side swing arm pivot bolt is now easily accessible.


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Figure 6 - Left Side Swing Arm Pivot Bolt Accessible


Before removing the swing arm bolts, the engine stabilizer links (“Tie-Link, 16232-04B”) need to be removed.  There is one rear link at the back of the engine under the engine mount, and two on the front.  With these removed, the engine can be be moved back and forth in the frame enough to be able to remove the engine bushings.  (The rear link has a ground strap bridging it.)


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Figure 7 - Rear Engine Stabilizer Link


One end of the top each front engine link needs to be detached. 

 

On my bike it was easier to remove the top link mounting bracket, rather than pull a bolt from the end of the link.

 

 

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Figure 8 - Top Front Engine Link



Next I removed the bolts that hold the mounting bracket for the bottom front engine link to the frame.


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Figure 9 - Bottom Front Engine Link



With the bike on the lift I removed the swing arm bolts.  The swing arm needs to be suspended with a strap to keep it from falling when the bolts are removed.  As mentioned, an air impact wrench helps a lot for this since the bolts connect to a pivot shaft that can easily rotate.  Even though the swing arm pivot shaft lockplate has locator tabs, they are small and it is easy to rotate the shaft if removed without an air wrench


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Figure 10 - Right Side, Swing Arm Pivot Bolt Removed



Over to the left side, and out comes the bolt…


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Figure 11 – Swing Arm Bolts Removed and Swing Arm Suspended



With the swing arm bolts removed, the swing arm can be pushed back to uncover the OEM rubber bushings.  The below picture shows the right side motor mount bushing. 


Before removing the right bushing, the left side bushing has got to be removed and the swing arm shaft pulled out on the left side.



Looking at the hollow area in the motor mount bushing around the swing arm shaft, it can be seen how much room for movement the rear of the engine, and hence the swing arm mounting shaft, has within the frame.



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Figure 12 - Right side OEM Swing Arm bushing



The left side swing arm bushing is held in place by a removable collar  - “Mount, rear isolator" (16301-08) fastened with two Torx screws.



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Figure 13 - Left side Swing Arm bushing



After removing the Torx screws the left side bushing’s mounting plate can be pulled off the OEM bushing.  If the plate is stuck, or hard to pull off, it can be pried at its edges and pulled off.



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Figure 14 - Removing the Left Side Bushing Collar



Once loosened, the mounting plate will lift off the left side bushing.


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Figure 15 – Isolator Mounting Plate on Left Side Engine Mount



With the mounting plate removed, the left side rubber motor mount bushing will pull off the swing arm shaft.  The left edge of the OEM bushing may touch the back of the engine case.  If so, the bushing may need to be pried slightly to let the edge clear the case.  The bushing can also be driven off from the back by using a long rod and a rubber mallet.


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Figure 16 - Left Side Rubber Bushing



And, off comes the OEM left bushing…


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Figure 17 - Left Side OEM rubber bushing, removed


With the left side bushing removed, the lockplate for the swing arm shaft is exposed.  Three Torx head screws need to be removed from the lockplate to take it off.


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Figure 18 – Swing Arm Shaft Lockplate



After removing the three Torx screws, the lockplate will slide off the left end of the swing arm pivot shaft.


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Figure 19 - Removing the Swing Arm Lockplate


Lockplate removed - ready to pull the pivot shaft out of the left side so that right side motor mount bushing can be removed.  The engine may need to be jacked to relieve pressure on the shaft.  With the shaft unloaded, it can be tapped out of the engine mounting point with a rubber mallet.


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Figure 20 – Swing Arm Shaft Exposed



Tapping the shaft out from the right side, here it is.  This shaft slides through the mounting point at the back of the engine.  The shaft in my XR1200 was lightly corroded and took a little convincing to slide out.


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Figure 21 – Swing Arm Shaft Removed


Shaft out - now back to the right side rubber motor mount bushing.  The right side bushing mounting plate is fixed in the frame.  Because the engine stabilizer tie-links are removed and the front engine mount is also rubber mounted, the engine can be pried toward the left a bit to remove the right side bushing.



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Figure 22 - Right Side OEM Rubber Bushing


In order to pry the engine enough to remove the bushing, the drive belt tensioner pulley does need to be removed.

 

A wooden mallet handle works well to move the engine enough to pop the right side bushing out of its mounting point.


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Figure 23 - Removing the Right Side Bushing



Old OEM Motor Mount vs New Vance & Hines


With the OEM hollow rubber bushings removed from the frame, the below picture shows a look at the difference between the OEM bushings and the Vance & Hines polypropylene mounting bushings.

 

The design difference between the OEM and V&H motor mounts is significant.  In the above pictures it can be seen that the swing arm shaft mounts solidly through the mounting hole in the rear of the engine.  The rubber OEM bushings are squeezed between the engine and the frame to hold the rear of the engine in place - but the hollow rubber bushings allow the engine to vibrate and move.  The swing arm shaft, and hence the swing arm, can vibrate and move within the open center area of the OEM bushings.  While the engine tie-links limit engine movement one can obviously watch the engine vibrate in the frame.  That gives an idea of how the swing arm can move relative to the frame, including while cornering. 


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Figure 24 - Comparing the Rubber to the Poly Bushings




Installing the Vance & Hines Polypropylene Motor Mounts

 

Installation of the V&H bushings is the reverse of removal of the stock bushings.  The outer ends of the V&H bushings are slightly smaller in diameter than the OEM bushings, so they clear the back of the engine more easily, and make assembly easier than removal.  The following pictures show what the install looks like.

 

First a little prep.  I coated the swing arm shaft with anti-seize before reinserting it.

I don’t have a picture of installing the right side poly bushing, but it is the reverse of removal.  The engine is pried to the side enough to insert the bushing, and it is put in place with its ears lining up with their spots in the fixed right mounting plate in the frame. The swing arm shaft is then reinserted from the left side of the engine.



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Figure 25 – Anti-seize on Swing Arm Shaft



Also, before putting things back together, notice the locking tabs on the shaft’s locking plate.  These line up with flat spots on the ring at the left end of the shaft.



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Figure 26 - Lockplate Locating Tabse


 

The lockplate locating tabs must be lined up on the swing arm shaft, and the shaft must be rotated to align the holes in the lockplate with the threaded screw holes on the engine case.  The below picture shows the lockplate on the pivot shaft, before the assembly is rotated to line up the screw holes.

 


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Figure 27 - Inserting the shaft



With the screw holes properly aligned and the lockplate locating tabs lined up with their spots on the swing arm shaft, the shaft looks like this.

 

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Figure 28 - Lockplate aligned


The lockplate Torx screws are then reinstalled and torqued to 80-120 in-lbs….

 


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Figure 29 – Swing Arm Shaft Lockplate Installed


Next the left side poly bushing is slid onto the swing arm shaft.  Since the outer diameter of the end of the V&H bushing is slightly smaller than the OEM rubber bushing, it will slide onto the shaft easier than the OEM bushing came off.

 

Looking at the picture below, it is easy to see how the V&H poly motor mounts position the swing arm solidly in the frame at both ends.  This ties the rear of the engine solidly into place.  The engine can now move up and down at the front, but won’t be able to move laterally or rotate to the sides. 

NOTE:  Solidly mounting the rear of the engine like this will transmit additional engine vibration into the frame, which could prematurely stress the frame.  Which, is why V&H makes you sign a disclaimer before they will sell you the poly bushings. 

On the other hand, since the poly bushings solidly locate the swing arm in the frame, the engine will no longer steer the rear wheel in corners.  No more lateral or twisting swing arm movement and more positive cornering.



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Figure 30 - Left Side Poly Bushing on Shaft


With the left side bushing installed on the swing arm shaft, its mounting plate can be slipped on, and the Torx screws that hold it in place reinstalled and torqued to 25-35 ft-lbs.

 


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Figure 31 - Left Side Isolator Mounting Plate Reinstalled


After the mounting plate on the left bushing is reinstalled, the swing arm can be slid back into place, its mounting bolts reinstalled and torqued to 60-70 ft-lbs. 


Finally, the miscellaneous XR1200 parts are reinstalled. 

 

Here is a look at the right side bushing in place and with the other XR1200 parts reinstalled.




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Figure 32 – Bushings installed


And here is a close-up of the left side bushing reinstalled, with all the miscellany in place….

 



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Figure 33 - Left Side Poly Bushing Complete


And, a look at the bottom of the rear engine/swing arm mount with the V&H poly bushings.


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Figure 34 - Poly Bushings Installed


The below picture shows the XR1200 fully reassembled, and ready to go carve corners more precisely.


The end result of the poly bushing install is more precise handling because the swing arm no longer floats, and hence the rear tire no longer moves and changes the steering line in hard or high speed cornering.  It also improves straight line tracking of the bike, and tracking through high-speed sweeping turns.



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Figure 35 - Voila!  The end!  Ready to really hold the corners...



Conclusion


The motor mounts are probably the most significant improvement to cornering, after fork/shock upgrades.  They improve what I would call a design deficiency in the attachment of the rear swing arm to the frame.  Ideally, the rear of the engine should float on the swing arm shaft, but not drive the swing arm and force the swing arm shaft to move in the frame.


The Effect of the Change

 

I’ll preface some comments on the cornering improvement due to the poly bushings by saying that my XR1200 never had any high-speed handling or vibration problems before this mod.  I run the XR1200X BPM forks with Andreani valves, and the Ohlins full adjustable rear shocks with riser blocks.  My preference is Dunlop GP-A racing tires, and I use them on the street.  I do have a steering stabilizer on the bike but have alternately run the bike on the track and up to 135 mph with and without it, and there was no difference.  People want to use the steering stabilizer as a band-aid fix for other problems but properly adjusted it should only come into play in a tank slapper – its benefit is its high-speed damping it shouldn’t be used to handle low-speed damping issues with normal turning or riding.  Anybody adjusting the stabilizer to have constant tension has it too tight.  Its benefit is its high-speed damping.  Front-end wobble problems are generally due to problems with tires or tire selection, tire air pressure, suspension adjustment or damage (not design), steering head adjustment, or rear wheel alignment.

 

With that said, after installing the V&H poly motor mounts I headed to Summit Point Raceway (aka Bill Scott Raceway) about an hour and a half outside of Washington, DC.  Summit Point Raceway’s main track is a 10 turn course with a short straightaway (about a ¼ mile  with a bend) that leads into a long straightaway (about ½ mile straight).  Turn 10 from the short straight into the long straight, is a fast corner.  I spent most of the time on the long straight at 110 to 135 mph. (Even the XR should be able to hit 140-145 on that straight, but I wasn’t geared right and wasn’t entering the long straight fast enough.)    What I noticed with the poly motor mounts was the ability to hold a more precise line through the turns, the ability to change lines in a corner more easily, and having to think less about the bike’s line in the straightaway above 120 mph.  I am thinking that on a track like Virginia International Raceway with a bend in the middle of the main straight, that the sense of relative speed will go down with the poly bushings because the bike will track straighter without effort.

 

So, all good with the Vance & Hines polypropylene motor mount upgrade for me!  They won’t be for everyone.  Anybody who is worried about their XR warranty won’t want them (if anybody still has a warranty), due to disclaimers regarding transmitting additional engine vibration to the frame.  People wanting a cushy ride won’t want them because you will notice the frame shake a little more when stopped.  On the street one can see that additional vibration is transmitted into the handlebars, as evidenced by the additional shake in the mirrors.  These bushings are for riders who like to corner and want to feel the road – not for long distance cruisers who want a damped ride.   

 

From my perspective, I wish I had installed these bushings three years ago.  Of course after riding the XR1200 with the stock bushings for a couple of years, I now have a much better feel for how they help improve cornering!





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