MOTOCROSS ACTION • MAY 2012 • www.motocrossactionmag

MX
ACT
ION
MOTOCROSS ACTION • MAY 2012 • www.motocrossactionmag.com
CCC
02970
MAY 2012
KX450F
YZ250
KTM
250SX
$4.99
Attn retailer: Please display until May 10
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BEST BANG FOR THE BUCK!
PIPE, CAM OR PISTON?
We build a full-race 2012 Honda CRF250. . . 18 times
T
he big three of the hop-up
world are pipes, cams and
pistons. This trinity of parts
comprises a major portion of every
serious race program. The question
is, what does each piece of the
hop-up puzzle bring to the overall
picture? The motocross world is full
of anecdotal stories of 65-horsepower
CRF450s with nothing more done to
them than one tooth skipped on the
camshaft sprocket and a muffler
modified with a butter knife. But
with the ravings of backyard
mechanics aside, the MXA wrecking
crew wanted to find out how much
power is in the big three—individually
and in combination.
IT WASN’T AN EASY TASK,
BUT WE FELT UP TO IT—ONCE
WE GOT OUR DUCKS IN A ROW.
THERE WERE FIVE DUCKS.
It wasn’t an easy task, but we felt
up to it—once we got our ducks in a
row. There were five ducks.
(1) Bike: We chose a 2012 Honda
CRF250 as our test bike. We needed
a brand-new, never-been-run CRF250
with a fresh piston for our starting
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point, so that when we installed a
new piston later in the procedure, it
wouldn’t run better because it was
new, or vice versa. Plus, we have a
lot of Honda CRF250 experience and
had been making multiple runs on
our well-used test bike to test pipes
and other products. This would give
us a good basis for comparison
when we did the race portion of
this test.
(2) Dyno: Since we needed to
make multiple dyno runs and test
every possible combination of cam,
exhaust and piston, we needed to
commandeer a dyno for what
turned out to be 18 different engine
combinations—plus the time it would
take us to put the cam in, take it
out, put the piston in, take it out,
and swap pipes, ignitions and other
test possibilities. All the dyno testing
had to be done under the same
atmospheric conditions on the same
dyno and on the same day. Luckily,
Bill Severa of Bill’s Pipes gave us the
run of his Corona race shop for a
whole day.
(3) Parts: We elected to use FMF
for our exhaust supplier because we
have had good luck with their
CRF250 Factory 4.1 pipe ($549.99)
and MegaBomb head pipe ($349.99).
We chose Vertex for the 14.6:1 highcompression GP piston ($250.00) and
$269.95 Hot Cams for the Stage 2
cam, plus a Hot Cams shim kit to set
the valves with. This project also
called for several gasket swaps,
which Cometic provided at $51.11.
(4) Manpower: A five-man crew—
which included MXA’s Jody Weisel,
MXA’s videographer Travis Fant, Hot
Cams’ Jay Clark, Kawasaki off-road
mechanic David O’Connor and Bill’s
Pipes’ Jeff Springman (to run the
dyno software)—was required to get
the job done.
(5) Strategy: Thanks to a
corporate-style flow chart that
explained each step of the 18 dyno
runs, the crew was able to tear
the engine apart and put it back
together as few times as humanly
possible to achieve our goals.
What did we want to know?
That was basic. How much power
does an aftermarket exhaust pipe
produce—and where is that power
focused? How much power can a
buyer expect from an aftermarket
cam—and where is that power
focused? And, how much power can
be found in a high-compression
piston—and where is that power
focused?
IF THOSE HAD BEEN OUR
ONLY GOALS, WE COULD
HAVE WALTZED THROUGH
THE PROGRAM IN A HANDFUL
OF DYNO RUNS AND STILL
HAD TIME FOR LUNCH AT
BURGER BIGGIE.
If those had been our only goals,
we could have waltzed through the
program in a handful of dyno runs
and still had time for lunch at Burger
Biggie. Unfortunately for the five-man
crew, we also wanted to test every
possible combination of the stock
cam, Hot Cams cam, stock exhaust,
FMF exhaust, stock piston and
Vertex piston, which meant that we
had to run a totally stock CRF250,
stock CRF250 with the FMF pipe,
CRF250 with the Hot Cams cam and
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STEP TWO: STEP TWO
INVOLVED NOTHING MORE
THAN BOLTING ON AN FMF
FACTORY 4.1 SYSTEM AND
STANDING BACK
In a class that has lots of high horsepower front runners, the CRF250 can use some
help. MXA wanted to make it faster and chart where the speed came from.
stock pipe, CRF250 with the Hot
Cams cam and FMF pipe, CRF250
with the Vertex high-compression
piston with the stock cam and stock
exhaust, CRF250 with the Vertex
piston and the Hot Cams cam and
FMF pipe, and so on—we broke the
project down into eight steps.
Step two: Step two involved
nothing more than bolting on a
titanium FMF Factory 4.1 system
and standing back. The 2012 Honda
CRF250 likes aftermarket exhaust
pipes—and perhaps it never met a
pipe that didn’t produce more power
than stock (because that is not a
hard target to hit).
The FMF Factory 4.1 RCT (with Ti
MegaBomb header) was a winner. It
made more power from idle to signoff—a lot more power. Horsepower
with the FMF pipe rose from 35.63
horses to 37.78. Even better, peak was
moved up 100 rpm, and the power
gain was most significant from 10,000
rpm to the rev limiter. From peak to
sign-off, the gain was five horsepower
on average. Good, very good.
We couldn’t help but be impressed
that the FMF Factory 4.1 made at
least two more horses than stock at
every step of the powerband and as
many as six horses at 11,000 rpm.
STEP ONE: TO GET STARTED,
WE NEEDED SEVERAL
BASELINE RUNS ON OUR
BRAND-NEW 2012 HONDA
CRF250—PLUS SOME EXTRA
TIME ON THE DYNO
BREAKING IN THE ENGINE
Step one: To get started, we
needed several baseline runs on our
brand-new 2012 Honda CRF250—
plus some extra time on the dyno
breaking in the engine (not critically
important, since we would be
putting new parts in it as we went
along; thus it would always be new).
The baseline runs would be used for
comparison to each mod.
The stock 2012 CRF250 engine
produced 35.63 horsepower on Bill’s
Pipe’s dyno on the day of the test.
The Honda has a nice dyno curve
that climbs steadily from a relatively
weak low-end to a healthy midrange
and a flat top-end. As we know from
testing and racing a 2012 CRF250 all
year long, the stock power delivery
is choked up by Honda’s longish
muffler and small perf core.
In stock trim the 2012 CRF250 feels choked down. We freed it up.
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BEST BANG FOR THE BUCK!
The FMF Factory 4.1
exhaust system boosted
the overall powerband and
didn’t require any technical
know-how to install.
STEP THREE: YOU DON’T
NEED TO BE DICK TRACY TO
REALIZE THAT ONE OF THE
REASONS WE CHOSE A CRF250
FOR THIS TEST—APART FROM
ITS POPULARITY—WAS THAT
IT HAS A SINGLE-OVERHEADCAM ENGINE
Step three: You don’t need to be
Dick Tracy to realize that one of the
reasons we chose a CRF250 for this
test—apart from its popularity—was
that it has a single-overhead-cam
engine. To those of us in the
trenches, that meant less spinning of
wrenches; one cam is easier to
change out than double overhead
cams—especially when you add in
shimming and adjusting. In step
three, we wanted to isolate the cam
and find out how much power was
hidden in the Honda CRF250
camshaft.
The $269.95 Hot Cams Stage 2 cam
mimicked the performance of the
FMF exhaust, but to a lesser degree.
Across the board, the Stage 2 cam
made more power than the stock
engine setup. Peak power with just
the Hot Cams cam installed was 37.18
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(compared to 37.78 horsepower for the
FMF pipe and 35.63 horses for the
stock engine). The Stage 2 cam was
degreed out to improve mid-and-up
power, which is exactly what it did.
Although the cam-equipped engine
produced more power from 5000 to
9000 rpm, those gains were in the
one horsepower range. But from 9000
rpm on, the Hot Cams cam jumped
up three horses over the stock engine
(admittedly less than with just the
FMF exhaust, but still impressive).
The gain from the middle to the top
was as advertised.
STEP FOUR: WE CAN BE
FORGIVEN FOR THINKING
THAT INCREASING THE
COMPRESSION ON THE CRF250
WITH A NEW VERTEX PISTON
WOULD BOOST THE LOW-TOMID TRANSITION—BUT SUCH
WAS NOT THE CASE.
Step four: We can be forgiven
for thinking that increasing the
compression on the CRF250 with a
new Vertex CRF250 GP piston would
boost the low-to-mid transition—but
such was not the case. The third
piece of the hop-up trinity was the
Vertex high-compression piston. It
would up the ratio from 12:1 to
14.6:1. Although the increased thrust
on the piston helped a little from idle
to 9000 rpm, we saw the biggest
gains from nine grand on up to
sign-off. This was most likely a
byproduct of the engine’s overall
setup. The piston mimicked what we
learned from the pipe and cam
before it. The FMF pipe showed the
biggest gains, with the Hot Cams
cam running second and the Vertex
piston in third. All three were better
than the stock engine setup.
The high-compression piston was
good for 36.77 horsepower at peak—
and peak was exactly where it was
on the stock engine. The piston
made more power down low than
the stock engine, but the Hot Cams
cam and FMF pipe, by themselves,
made more power off the bottom.
From 9000 rpm on, the piston
produced approximately 1-1/2
horsepower more than the stock
engine all the way to sign-off.
At this stage of the test, MXA was
convinced that, individually, each
piece of the hop-up puzzle added to
the performance of the overall
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combination—the FMF pipe and Hot
Cams cam. This required a minor
leap of faith because we had to
assume that a CRF250 racer would
buy a pipe, but skip the cam and go
straight to the piston. We made this
slightly illogical jump by telling
ourselves that if a guy had a CRF250
with an aftermarket exhaust, he
would end up with a high-compression piston—but no aftermarket cam—
during the rebuild process.
By mating the FMF pipe with the
Vertex piston, we again gained the
bottom-end burst of the pipe, and
the powerband was still very strong
from the middle to the top. Much
stronger than stock, peak horsepower with the pipe/piston combo
was 37.85 horsepower. This was less
than with the pipe/cam combo, but
more than the pipe, cam or piston
could produce by themselves.
It took us 18 different dyno runs to find out what we wanted to know. Amazingly,
this small handful of parts, plus the pipe, was all we used in our search for power.
CRF250 package. In descending
order, the FMF exhaust, Hot Cams
cam and Vertex piston all added
power. The next step was to start
putting the pieces together.
STEP FIVE: COMMON SENSE
TOLD US THAT ONCE A CRF250
RACER BOUGHT A PIPE,
HIS NEXT MOVE WOULD BE
TO INSTALL A HIGHPERFORMANCE CAM.
Step five: Common sense told us
that once a CRF250 racer bought a
pipe, his next move would be to
install a high-performance cam.
Thus we set out to dyno-test an
engine configured with the FMF
pipe and Hot Cams cam against the
stocker—and the stocker with just a
pipe, or the stocker with just a
cam.
No need to hem and haw; the
FMF pipe and Hot Cams cam
rocked. The horsepower with this
configuration jumped to 39.40. That
is 3.77 horsepower more than the
stock engine, 1.62 horsepower more
than with just the FMF Factory 4.1
exhaust pipe, and 2.22 horsepower
more than just the Hot Cams cam.
By combining the FMF pipe with the
Stage 2 cam, we gained the
improved bottom-end that the pipe
exhibited and enhanced the middle
and top with the cam and pipe’s
mid-and-up pluses.
STEP SIX: THE NEXT
LOGICAL STEP WAS TO COMBINE THE FMF PIPE WITH THE
VERTEX HIGH-COMPRESSION
PISTON AND LEAVE THE HOT
CAMS CAM OUT OF THE MIX.
Step six: The next logical step
was to combine the FMF pipe with
the Vertex high-compression piston
and leave the Hot Cams Stage 2 cam
out of the mix. This would give us
an across-the-board comparison to
what, up to this point, was the best
STEP SEVEN: THE SILVER
BULLET WAS TO PUT ALL OF
THE PIECES TOGETHER AND
TWEAK THEM A LITTLE TO
SEE WHAT WE COULD GET
OUT OF THE CRF250.
Step seven: The silver bullet was
to put all of the pieces together and
tweak them a little to see what we
could get out of the CRF250. We
were cracking the edge of 40 horsepower and knew in our heart of
hearts that if we put the Hot Cams
Stage 2 cam, Vertex high-compression piston and FMF Factory 4.1
pipe together that we would crack
the magic number. So, after a few
runs of various combinations that
were required by the rules of the
scientific survey, we were finally
ready for the ultimate test. We
The cam change required reshimming of the valves. We used a Hot Cams shim kit
to make the job easy. The single cam of the CRF250 was a blessing.
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BEST BANG FOR
THE BUCK!
On the track, the biggest gains were from the middle on up. The full-race CRF250 revved quicker and revved higher. It lost its
muffled feel and pulled harder across the meat of the powerband. With a little cheating, we got close to 40 horsepower.
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With the cam out of the Honda cylinder head, you can see the simplicity of the Honda Unicam design. The exhaust valves are
actuated by the forked rocker arm (right), while the intakes are operated by a shim under bucket system (left).
installed the high-comp piston, Stage
2 cam, and FMF exhaust on our
CRF250 and waited for the ticker
tape to fall from the ceiling.
The results? We hit 39.03 horsepower. There was no joy in Mudville.
We were disappointed, because
although that was an awesome
horsepower number, we had made
more horsepower with just the FMF
pipe and Hot Cams cam (39.40) than
with the pipe, cam and piston.
STEP EIGHT: WE HAD COME
TOO FAR AND LEARNED TOO
MUCH TO STOP. EVERYTHING
RESTED ON THE EIGHTH
STEP OF OUR EIGHT-STEP
PROTOCOL. WE ADMIT THAT
STEP EIGHT INVOLVED SOME
CHEATING, THOUGH.
Step eight: We had come too far
and learned too much to stop.
Everything rested on the eighth step
of our eight-step protocol. We admit
that step eight involved some
cheating, but we decided to remove
the backfire screen from the CRF250
airbox and hook up a Tokyo
Mods/Vortex ignition box. In many
ways we were violating our whole
test because we hadn’t run individual
dyno runs on the ignition mapping or
removed the airbox screen, but at this
point, we wanted to crack 40 horsepower—because that would not only
be a 4-1/2 horsepower gain over
stock, but a tremendous increase in
horsepower from 7000 rpm to sign-off.
We fired up the bike for one last
series of runs, crossed our fingers, held
our ears and peered intently at the
computer readout. Bingo! The numbers
peaked out, and everyone gathered
around the computer to see the final
number. It was...39.83 horsepower.
In truth, we were happy with the
final run because we had gained
horsepower with a couple of simple
mods—and one of them was free. All
that was left was to take all of the
dyno sheets—there were 18 of them—
and try to make sense out of what
we had learned.
LET’S PUT MONEY AND
COMPLEXITY ASIDE FOR
THE MOMENT AND TRY TO
DECIPHER WHICH MOD GAVE
THE BIGGEST BANG (WITHOUT
CONSIDERING THE BUCK).
Conclusion: Let’s put money and
complexity aside for the moment and
try to decipher which mod gave the
biggest bang (without considering
the buck).
(1) FMF exhaust: If you want to
get the most out of your CRF250
with a single mod (and something
that a monkey with a nutcracker
could install), go with the FMF
Factory 4.1 exhaust. It changed the
whole personality of the 2012
CRF250—from doggy to pedigree. It
livened up the throttle response,
bolstered the lackluster low-end and
roared across the middle. Great mod,
but it has a healthy price tag.
(2) Hot Cams Stage 2 cam: The
cam by itself was good, but we can’t
see anyone running the stock exhaust
system and popping for a $269.95
cam. When you pair the Hot Cams
cam with the FMF pipe, you get
incredible performance. Yes, our fullrace mod—with pipe, cam, piston,
ignition and airbox—made 4/10th of a
horsepower more at peak, but it
didn’t blow the pipe and cam out of
the water. For a CRF250 owner who
can install a cam by himself, this is
the best buy.
(3) The kitchen sink: When we
threw out the rules—which, like AMA
rules, were enforced loosely—we
were able to produce close to 40
horsepower. These gains were mostly
due to the added revs of the ignition
mapping. Before we added the
ignition and cut the wire screen out
of the airbox, the whole kit and
kaboodle (pipe, cams and piston)
couldn’t beat just the pipe and cam.
For more information, visit
www.vertexpistons.com, www.hot
camsinc.com, www.cometic.com and
www.fmfracing.com.
So there you have it; a complete
breakdown of the who, what, why and
where of the three most popular hopup parts offered to local racers. We
know what we would do—do you? ❏
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