You are forgiven if you are a Honda CRF450, Kawasaki KX450F or KTM
450SXF owner and you don’t give a twit about hopped-up Yamaha YZ450Fs.
You may be thinking, “Yamaha? I don’t own a Yamaha and don’t want to
read about them.” But, you know deep down inside your insecure heart
that you do want to know everything there is to know about the 2010
Yamaha YZ450F. Why? Because that is your competition.
The YZ450F was all-new in 2010, and every racer, on every brand, has to
wonder if the YZ450F’s backwards cylinder, offset crankshaft, tilted
top-end, downdraft fuel injection and creative frame offer a significant
advantage over his trusty, but rusty, race bike.
In the 2010 MXA 450 Shootout, the Yamaha YZ450F finished second overall
(behind the KTM, but in front of the CRF and KX-F). The MXA wrecking
crews thinks that the Yamaha YZ450F is a solid machine with innovative
credentials. It has a typically abrupt, low-to-mid, fuel-injected
powerband; is relatively flat on top; and does not come near the
horsepower output of the KX450F or 450SXF. As for the handling, the
YZ450F feels light in roll, pitch and yaw, but since it is heavier than
the 2009 YZ450F, some of the benefits brought on by centralization of
mass are muted. The front end has a no-bite feel on the entrance to
turns, but overall it handles decently. All in all, the 2010 Yamaha
YZ450F is a good motocross bike—not a great one, though, because it
needs more power, improved top end and a sleeker layout.
To that end, the MXA wrecking crew ordered up four full-race, hopped-up
2010 YZ450F project bikes. We told Hot Cams, AP?Racing, Yoshimura and
Pro Circuit that there were no holds barred—choke holds, arm bars and
knee drops were allowed. They were asked to build the ultimate
expression of what a YZ450F could be.
What follows is what the MXA test riders thought about the four YZs......this is a test of one of them—Hot Cams' YZ450F. Over the last two weeks we have tested Yoshimura's and AP Brakes' YZ450F and you can find them on the home page.
WE TEST THE HOT CAMS YAMAHA YZ450F
ALL THE PERTINENT FACTS
Here are the details, prices and parts used on Hot Cams’ 2010 Yamaha YZ450F:
1. Hot Cams 4169 INBLD intake cam ($229.95).
2. Hot Cams 4171 EXBLD exhaust cam ($229.95).
3. Recommended valve clearance is 3 to 5 on intake and 5 to 7 on the exhaust.
4. Hot Cams 9.48mm valve shim kit ($89.95).
5. Injectioneering throttle body modification ($240.00).
6. Hinson clutch cover, inner hub/pressure plate kit, billet clutch basket, fibers, steels, springs.
7. Uni Filter air filter ($20.95).
8. Renthal 14/48 chainwheel combo.
9. Custom modified shrouds, air scoops and mapping by Tom Morgan of Hot Cams.
1. FMF Anodized RCT factory 4.1 complete exhaust system with titanium Megabomb header ($899.99).
1. Enzo revalve for initial plushness and better bottoming resistance
($180), stiffer 0.48kg/mm springs ($110), DLC (diamond-like coating) on
fork legs ($450) and Enzo 24mm offset fork lugs with axle ($1000).
1. Enzo revalve ($180).
2. Enzo lowering plate for 3mm shortened shock shaft ($40).
1. CV4 silicone coolant hoses ($97.95).
2. Works Connection Elite perch, front billet brake cover, rear billet brake cover, engine plugs and radiator braces.
3. DeCal Works custom graphics kit.
4. Dunlop MX51 rear and 745 front tires.
5. Renthal 997 TwinWall bars, dual-compound grips, rear sprocket and MX chain.
Hot Cams: www.hotcamsinc.com or (515) 402-8005.
FMF Racing: www.fmfracing.com or (310) 631-4363.
CV4: www.cv4.net or (800) 874-1223.
Hinson Clutch Components: www.hinsonracing.com or (909) 946-2942.
Works Connection: www.worksconnection.com or (800) 349-1475.
DeCal Works: www.decalmx.com or (815) 784-4000.
Dunlop Tire: www.dunlopmotorcycle.com or (800) 845-8378.
Renthal: www.renthal.com or (877) 736-8425.
Uni Filter: www.unifilter.com or (714) 535-6933.
ENGINE BY HOT CAMS AND SUSPENSION BY ENZO
The high-tech 2010 YZ450F is the type of bike a backyard mechanic can
really mess up trying to modify. On the other hand, experienced engine
tuners like Tom Morgan and Hot Cams see the bike as a shining
opportunity to sink their teeth into something challenging. Former
factory mechanic Tom Morgan gained respect for Yamaha’s engineers while
working on the YZ450F. He feels that the blue machine is one of the most
sensitive bikes to get power out of—and that traditional hop-ups, like
high-compression pistons, have to be used intelligently.
Naturally, the first place Hot Cams looked for improvement was in the
camshafts. Hot Cams has developed a wide variety of cams for
every customer’s needs: from average Joes to experienced engine tuners,
and from offroad torque monsters to AMA National rev rangers.
There are five Hot Cam options (which include intake and exhaust but can be mixed and matched) for the YZ450F:
The Stage One cam offers more torque and power up to 9000 rpm and mimics
the stocker after that. Their Torque cam has even more power at partial
throttle openings and low rpm. The Stage Two cam offers the same
bottom-end power as stock, but more power on top. There are two cams in
Hot Cams’ new “Builder Series” that are meant for more serious tuners
(as part of a custom package). The first set of “Builder Series” cams,
featured in our project bike, offers more top-end power than the Stage
Two cam. The second Builder cam is an even larger step up in high-rpm
power and is meant for a supermoto guy or a big-bore engine tuner.
Cams were just one piece of the Yamaha puzzle, and Morgan and Hot Cams
had to figure out all the other unique aspects of the YZ450F. First was
the intake. They played around a lot with the shrouds and air scoops to
open it up and let more air in while keeping heat and excess dirt away
from the radiators. Morgan says cams can produce 2 to 3 more horsepower
if the bike can get the air it needs.
EFI mapping was also crucial. Hot Cams conducted dyno testing with
programs that collect data at all rpm, throttle openings and various
engine loads. From this testing, custom fuel and ignition maps were
developed by looking at mixture ratios for all conditions.
Hot Cams’ overall goal for the YZ450F project bike was based on the
common complaints that they experienced with the 2010 YZ450F. First was
to make the initial power less abrupt. Second was to create more power
over a wider rpm range. And third was to boost the peak horsepower.
MXA TEST RIDER COMMENTS:
“The power was very broad. It wasn’t quick or snappy, but very torquey.
It revved in a very metered fashion that made it easy to use on the
track. It felt fast, but it didn’t take a lot of work to hang on to.”
“The power was stronger than the stock YZ450F in the bottom and
mid, and it pulled farther. It didn’t seem all that fast in the top-end,
but it would pull, which is something that the stocker won’t do. I
didn’t have to shift very often because it had the oomph to pull the
“I liked this engine because it had a chunky, broad and torquey feel. It
felt powerful, but wasn’t jerky or arm stretching. It had excellent
bottom and middle.”
“I don’t know if it was the fork lugs or suspension valving or
both, but this YZ450F didn’t have the knife-in tendency that others do.
Switching back and forth from stock offset to Enzo’s 24mm offset was a
night-and-day difference. A lot of the oversteer and tucking-in tendency
of the front when leaning in turns was gone. It was more stable on
straight-line acceleration and braking, too.”
“I was pretty impressed with the suspension. The first fork setting I
tried stayed in the mid-part of the stroke and deflected halfway through
the turn. Luckily, Will Decker from Enzo was at the track with us. He
took the forks apart, fixed the problem and made them plush all the way
through. It was a big difference. The shock settled nicely and worked
well on acceleration.”
“Often I have a problem with the stock Yamaha shock heating up and
losing performance in long motos. This shock worked all the way through
“I liked the forks, but the rear was just okay. The forks were really
plush and soaked up all the little bumps. They were predictable all the
way through their stroke. The shock seemed to be stagey. It moved twice
through each stroke. Smooth, then stiff, then smooth.”
“Overall, I felt that the Enzo/Hot Cams collaboration produced a
bike that was quite a bit different from the stock YZ450F. Where the
stocker is abrupt, barky and short-winded, the Hot Cams engine was very
old school. It depended more on torque than burst. In the suspension
department, Enzo did great things with the forks, but the shock got
Yamaha Motorcycle tests