XR1200 Gearing Calculations for Stock and Modified Gearing

The U.S. and general international models of the XR1200 come with 34-57 primary gearing, and 28-68 final drive gearing.  While the 34-57 gearing is more common to a 883 XL than other HD 1200 Sportster models, it does give the XR1200 a quicker feel of acceleration. 
XR1200 riders like to change this gearing for a variety of reasons - e.g. higher top end speed, more control with a built engine, or lower rpm while cruising at highway speeds.  This is an easy gearing change using HD Sportster parts that come stock on XR1200's destined for Brazil and Japan.
The calculations on these pages give an idea of the effect of various gearing changes on top speed, shift points, and rpm at highway speeds.
For these calculations I only looked at gearing changes for the stock belt drive, i.e. I did not look at swapping out the drive belt for a chain.  I ran the calculations for a variety of gearing options that are easily obtained with stock HD and/or commonly available gears/pulleys.

The stock XR1200 comes with a  34 tooth gear on the crankshaft in the primary, and a 57 tooth gear ring on the clutch basket. - for U.S. and International versions.  The Brazilian and Japanese versions come stock with a 38 tooth front primary pulley.
Also, the stock XR1200 transmission pulley has 28 teeth and the rear wheel pulley has 68 teeth. on all versions.
Except where noted, these calculations  are done using a nominal tire diameter of 24.8" for the stock 180/55 17" rear tire.
To give you an idea of the speeds possible in each gear, here are the gearing calculations, with mph vs rpm tables at 3,000 and 6,800 rpm.  (6,800 rpm is the redline on a stock bike.) 
NOTE:  All of the calculations on these pages were done with the gearing calculator on BigBoyz Cycles web page.  That particular calculater does not have a dropdown option for the Sportster, so I've manually inserted the parameters for the XR1200 vice the "09 Big Twin" default title at the top of each page.  Also, while the charts show a nominal drive belt length of 139 tooth for a typical measurement between the center of the transmission pulley and rear axle, the actual XR1200 belt length is 137 tooth.

34-57 Primary Gearing with the stock 28 Tooth Transmission Pulley and stock 68 tooth Rear wheel pulley

Here is a look at the gearing calculations of a stock U.S./"International" XR1200 at 3,000 rpm.

34-57-28-68 with 180 Tire at 3000 rpm

As can be seen below, with the 34 tooth front primary gear, the XR1200 has a top speed of about 125 mph.

34-57-28-68 with 180 tire at 6800 rpm


A common gearing change is to switch the XR1200's 34 tooth primary gear for the 38 tooth primary gear (HD part number 30029-08 with 96-link primary chain 40147-04)  that is used on the Brazilian and Japanese XR1200 models
Although not for everyone, for riders who want to drop their rpm by about 400 RPM while cruising at 70 mph on the highway, this can be a nice change.  This also increases the top speed by about 15 mph.  XR1200's with engine improvements can easily pull this gearing combination.
One nice thing about this change is that the speedometer remains accurately calibrated.


It is also possible to install a 29 tooth front drive pulley (HD part number 40409-04) on the transmission.  This is the pulley used on all current US 1200  Sportsters, and can be used with the XR1200's stock 137 tooth drive belt and the 68 tooth pulley on the rear wheel.
I ran the 38 tooth primary gearing with the 29 tooth transmission pulley for about a year.  It was a nice gear combo that worked well with the ported heads and cams that I was running.  A consideration here, is that the speedometer will be off by about 2-3 mph, if you do not recalibrate.


Finally, it is possible to install a 30 tooth tranny pulley (HD part number 40380-04) with the stock 68 rear wheel pulley.  This is the pulley used for some of the V&H race series races.  It will work with the stock 137 tooth drive belt, but adjustment will be run to the very end of the rear wheel adjuster limit.
I ran the 38 tooth primary gearing with the 30-68 for a month and liked it on the street.  I tried it on the drag strip also, and felt that it cut down acceleration too much.  Even with the power curve of my built engine, I ended up going back to the stock 28-68 final drive.

Before you go on, here is a suggestion if you decide to install the 66tooth rear wheel pulley -   The Vance and Hines 66t rear pulley is about 0.365" thicker than the stock 68t pulley.  That means that the pulley mounting bolts will not seat as deeply into the rear wheel.  So, when installing the 66t pulley with stock bolts and washers, there will be less than 0.5" of thread engagement.  This does not appear to be enough thread engagement to reliably support the 80 ft-lbs of torque spec'd for the bolts by HD!  I highly recommend using 2.25" (7/16-14) bolts when installing the V&H 66t rear pulley.  Alternately, one could use a more conventional rear pulley bolt toque of 55-65 ft-lbs (as in earlier Sportsters) with Loctite - but the torque value that HD specs for the 2009 Sportster pulley bolts is too high for the stock bolts, when used with the V&H pulley.



A nice change for a modified XR1200, a racer, or a tourist who is really looking to drop rpm at highway speeds is to install the 66 tooth rear wheel pulley with the 29 tooth transmission pulley and the 38 tooth primary gear.  This change will boost the speed at 6800 rpm to about 147 mph and drop the 5th gear rpm at 60 mph to 2900.  To really take advantage of the top end though, takes a well tuned or modified engine - but for a tourist the lower rpm in the 60 - 80 mph range can be nice.
This combination was tough for me to set up with the stock 137 tooth drive belt.  I had a clearance problem with the bottom shock moung bolt and would likely have needed to change belt length to a slightly shorter belt to take this to the street.

Here are the gearing calculations for this combination.



The next step for a modified XR1200, or some racers dependent on course, is to install a 30 tooth transmission pulley (HD part number 40380-04) with the 66 tooth rear wheel pulley and the 38 tooth primary gear.  This change will boost the speed at 6800 rpm to about 152 mph. 
This gearing combination would work well on high speed tracks.  However, it may be more than the majority of street riders require.  It will also take a strong engine to pull the top end.  The stock 137 tooth drive belt can still be used with these gears.

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