New OEM XL1200R and XB Heads Are Now
Available Assembled from NRHS!
XB and 2004 XL1200R cylinder heads represent a major step forward in
port design from previous OEM cylinder heads. When comparing stock to
stock, our testing has shown these heads to be capable of 5-6 more
horsepower than typical Thunderstorm heads! Complementing the much
improved ports is a set of special lightweight large-diameter valves,
single beehive style springs with extra travel, ultra-lightweight
retainers & keepers, and an improved valve stem seal design. As a result
of these improvements, the new XB/04XL heads are quickly becoming the
OEM performance head of choice for XL's and Buells.
NRHS takes the hassle and expense out of using these new
now, these heads were only available unassembled.
NRHS now offers these heads professionally assembled with premium
Hurricane valves for the same price as all of the
individual stock components would cost you at your dealer!
We'll also drill and tap the breather holes for an extra $50
charge if desired on the XB heads. Other options include chamber work to accommodate
angle dome pistons at your desired compression ratio, heavy duty valve
train components, black powder coating, and Stage 1, 2, or 3 porting
services. We also offer pushrods and pushrod cover kits as well as a Buell front engine mount to simplify the installation.
heads feature 1.810" intake and 1.580" exhaust valves, the same size as
Thunderstorm, but with 7mm stems for additional weight savings. A single
beehive style valve spring controls each valve, further reducing weight
at the critical top end of the spring which sees the most movement. The
springs measure about 135lbs at 1.850" installed height when new. A new
improved valve guide seal design is used as well. There is plenty of
retainer-to-guide seal clearance and coil bind clearance to allow up to
.550" of valve lift, a full .050" more than the earlier heads, opening
up the possibility of using higher lift cams*. The heads use a bathtub
style 62cc chamber with flat squish bands. At stock 1200 bore and
stroke, this chamber provides approximately a 9.7:1 compression ratio
with flat tops. The XB and 2004 XL1200R heads are identical in every way
except the finish and the breather holes, which are already drilled and
tapped on the 1200R heads but not on the XB heads (the XB heads already
have the boss, however).
Professional Assembly Makes the Difference
During assembly, all new parts are used, and
premium quality Hurricane stainless steel valves are installed (1.810
intake, 1.580" exhaust, 7mm stems). Stem protrusion is checked and
adjusted as needed. Valve springs are fully tested for correct seat
pressure and travel, and valve spring installed height is set.
Valve-to-valve clearance is checked and we will advise if additional
work is needed to correct (this is primarily a function of the cams you
choose; cams with a lot of overlap may require clearancing work).
Exhaust studs are installed. With XB heads, we'll drill and tap the
breather holes if needed for an extra $50 charge. (04 XL heads already have these holes drilled
and tapped). We can optionally shim the springs for additional seat
pressure if needed for your cams*. All of that is done at no extra
charge! For only a little bit more, we can cut the combustion chambers
for an angled squish band and/or to achieve a desired compression ratio.
And of course, if you'd like everything you can get out of these heads,
we can fully port and flow them as well as fit ultra-high performance
Hurricane valvetrain components. We've made as much as 125rwhp at 1250cc
with Stage 3 ported XB heads, totally streetable!
* - Be careful about how aggressive of a cam lobe and how
much spring pressure you put to OEM valves with 7mm stems. A big part of
H-D's ability to get 7500rpm safely from these light duty components in
the XB9 is the gentle profile of the stock XB cam lobes. We recommend
converting to heavy duty Hurricane springs and Hurricane valves with
5/16" stems when using aggressive cam lobes.
rocker boxes bolt right up and the stock XL pushrod tubes work fine.
Your stock pushrods may or may not work, because these heads are about
.025" shorter than an XL or Thunderstorm head. By itself, this is
generally not enough to necessitate custom pushrods. However, if you are
shortening the stack further with additional milling to raise
compression, milling of your cylinders, and/or thinner than stock
gaskets, pushrod length may become a concern. The best way to determine
if pushrod length is an issue is to measure the amount of lifter plunger
preload you're getting, ideally the plunger should be centered in it's
travel when the valves are closed (stock lifters have .200" of travel).
We recommend correcting the pushrod length if the plunger is more than
.050" away from centered. Pushrod length can be corrected by using
Hurricane pushrods, which are available in either fully adjustable or
fixed length versions. When using adjustable pushrods, we highly
recommend a set of collapsible pushrod covers to facilitate adjustment.
the right (pushrod side) front mounting hole on these heads is moved
inward 1/4" from previous Evolution XL heads. Modification of your
engine mount may be required.
86-03 Sportster owners we now offer a steel mount that has the mounting
hole correctly located. It is zinc plated so it will require
painting or call us about powder coating services available.
For even more performance, check out our
XL/Buell Head Porting Services
Stage 2 XB heads cut with a 15 degree angled squish
band and chamber
relief work to give 10.5:1 compression with
Thunderstorm type pistons.
The 15 degree angle provides the air with a more
direct path into and out
of the cylinder as compared to the stock flat squish
improving cylinder fill, and also directs the fuel
being squeezed out of the
squish band more directly at the flame front. This
angle also maintains
good squish band area for a given dome height, which
turbulence and minimizes detonation. We recommend the
15 degree angle
for most street applications with moderate dome
heights and compression ratios.
The top of the line! These Stage 3 XL1200R heads have
with a 30 degree angled squish band
for special application
racing pistons. The extra-large 1.900" intake valves
heavily unshrouded for maximum flow, and the 30 degree
complements this nicely by reducing even further the
the air must go around to fill the cylinder. Since it
area at a given dome height, this angle is best suited
dome, higher compression pistons as commonly
found in racing
or very hot street applications.
All chamber work is done on a state-of-the-art CNC
ensure quality and accuracy.