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:

ENGINE:
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.

EXHAUST:
1. FMF Anodized RCT factory 4.1 complete exhaust system with titanium Megabomb header ($899.99).

FORKS:
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).

SHOCK:
1. Enzo revalve ($180).
2. Enzo lowering plate for 3mm shortened shock shaft ($40).

ACCESSORIES:
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.

CONTACTS:
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 gears.”

“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 30-minute motos.”

“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 mixed reviews.”