MAX BIKES: May 2011

The KX450F is an interesting motorcycle, with a contradictory personality. Its reputation for having brute power comes at the expense of agility. Each year Kawasaki tries to calm the monster to better suit the average rider, but even a kinder, gentler monster is still a monster. Still, that personality disorder shows up in the weirdest places. WORCS race, the desert, GNCC, Endurocross… there is obviously more to the green meanie than meets the eye.

2011 Kawasaki KX450F

Kawasaki made changes to the 2011 KX450F to make it easier to ride and more reliable.

The Monster Energy Kawasaki off-road team and scores of privateers race the KX450Fs with great success in all sorts of venues far removed from the cut and thrust world of Supercross or Outdoor motocross. Don’t forget, a few years ago during a contract dispute World Enduro star David Knight quit his team and flew to the U.S, bought a KX450F with his own money and rode it in bone stock condition that very weekend to a GNCC win. We knew from our tests of the 2010 and 2011 KX250Fs that they were great motocross bikes that just happen to also be great off-road race bikes too. But even with the 450’s fine off-road credentials it still seemed hard to believe that the holeshot king of 450-class motocross could be tamed enough to work anywhere but on the track. We decided to find out, and have been spending the past few months learning about the 2011 KX450F by riding it everywhere from frozen lakes to sloppy cross-country races, on motocross tracks and in tight singletrack.

2011 Kawasaki KX450F

We rode the 2011 KX450F everywhere, even comparing it to a 2010 KX450F on a frozen lake.

Kawasaki smoothed out the violent bottom-end hit a little for 2011, but this is not the kind of motorcycle you ride with finesse. Point and shoot. Acceleration remains the big Kawasaki’s greatest asset, so take advantage of it at every opportunity! Yes, the KX450F is as strong as legend states. These things absolutely rip, from bottom to top, even in a ‘toned-down for 2011’ state of tune.

In 2010 Kawasaki introduced the bridged-box bottom piston, which improved reliability and also allowed more top-end and overrev power. The cylinder and crankcase were reinforced and cam timing was altered. Kawasaki modified the piston shape again for 2011 to better suit a new, quieter 94dbA silencer.

Fuel-injection mapping has been changed to provide smoother low-end response, and the shift mechanism was upgraded with stronger springs and a larger internal roller. The 450 Kawi engine has 12.5:1 compression, with a wedge-shaped crank web that produces an effective “counterweight” effect that reduces vibration, improves power delivery and enhances low-rpm throttle response. Kawasaki claims the engine can be started within three rotations. We found the KX450F to be the easiest starting (and hardest to stall!) 450 motocross bike we’ve tested.

2011 Kawasaki KX450F

The clutch pull is quite easy on the KX450F… maybe too easy. Heavier clutch springs will help improve clutch life.

The clutch is light and progressive, and while Kawasaki improved clutch friction material for 2011, the plates still wear quickly. Stiffer clutch springs will help, but the hot tip from Kawasaki Canada’s flat track Pro Johnny Parker is to mill the clutch basket so the springs have a little higher preload. Parker also advises KX450F owners to check the oil pickup screen on the oil pump immediately after the bike is broken in. The 2010 and 2011 we had were both fine, but it is not unknown to find them partially plugged with excess silicone.

Kawasaki’s optional EFI Calibration kit has been updated for 2011 to make it more user friendly. The Digital Fuel Injection (DFI) system automatically adjusts to suit track and climate conditions, but there are a selection of pre-set ‘soft’ to ‘hard’ maps in the ECU which can be accessed with the EFI Calibration Kit. The DFI is also infinitely adjustable, so you can design your own fuel and spark curves. The Calibration Kit includes a data logger that records the past six hours of engine rpm, throttle opening, coolant and air temperatures, ignition timing, fuel adjustments, gear position and system voltage.

2011 Kawasaki KX450F

The magic box. Kawasaki’s optional EFI Calibration kit makes infinite tuning changes possible.

New engine mounts for 2011 improved chassis flex, and the forks and shock received more civilized damping settings. Between the smoother powerband and more compliant suspension when ridden back to back with the 2010 model, the 2011 almost feels like an enduro bike – a very powerful enduro bike, that is. KX450Fs are notorious for eating up chain guides, so Kawasaki upgraded to a new guide that it claims is three-times more durable than in 2010. Unfortunately the lightweight drive chain would barley be adequate on a 125. If you buy a KX450F you should install a high-quality sealed chain before you even ride it.

The beauty of the KX450F lies in its versatility. With the ECU mapping set to the softest curve, the KX can even be a fun hardcore trail bike for a strong, aggressive rider. With tons of power and huge aftermarket support you can make a KX450F into a very effective flat track racer, supermoto or cross-country race bike. Naturally the KX450F thrives on high-speed courses, but this is a big motorcycle that is heavier than most other bikes in its class. Cutting and thrusting around a motocross track with big berms works fine, but carving smooth arcs around sweeping high-speed turns is difficult.

The chassis takes some of the blame for the less than accurate steering precision, but much of the difficulty lies in the power delivery and gappy- feeling transmission ratios. The KX450F may be softer and gentler for 2011, but any twitch of throttle makes it lurch forward. If you modulate the throttle with the clutch it helps; the ‘non clutch abusers’ of our test crew had the most trouble adapting to the KX450F while ‘chronic clutch slippers’ got along better.

2011 Kawasaki KX450F

Find a berm, the bigger the better. The Kawasaki is happiest when you point and shoot.

Softer ECU mapping helps, but you can go a step further. John Parker and Hot Cams have been working hard to design cam profiles that provide smoother low to mid response. When we rode Parker’s Kawasaki Canada 2011 KX450F on the ice (modified with different cams, cylinder head porting and a stepped header pipe) alongside a stock 2010 KX450F, Parker’s factory bike felt slow. If you were on it with nobody around you’d swear it was a dog. Back to back with a stock bike the reality was Parker’s factory bike was way stronger than stock, only easier to ride. So the potential is there to make the KX450F into a gentle giant.

2011 Kawasaki KX450F

We had a riot confusing photographers by switching test riders back and forth between 2011 and 2010 models. We prefer the smoother 2011 model most of the time. The 2010 does pull harder off the bottom end of the powerband.

When we rode the 2011 at a tight motocross track alongside a stock 2010 model, we found the low-end burst wasn’t as difficult to manage as it was on the higher-speed grass track. In fact the quick throttle response comes in handy on a man-made motocross track, but the biggest issue with going fast on the KX450F is finding traction. We struggled with fork height and different suspension settings to find the right balance between predictable rear wheel traction and turning ability but were never entirely satisfied.

Get used to the KX450F and it feels okay, but if you ride another 450 you realize how awkward the Kawasaki feels in turns and how easily the back end steps out of line when you’re on the gas. The suspension is average, and our test pilots from Vet to Intermediate to Pro all rated the suspension action at both ends between 5 and 7 out of 10. We were happiest with the fork 5mm above the top triple clamp, the shock’s high speed compression backed off to 1.5 turns out and the compression and rebound at eight clicks out. The KX450F liked a little more sag than normal to find traction as well, in the range of 105 to 107mm. We liked the fork with eight clicks of compression and 10 rebound as our base settings.

2011 Kawasaki KX450F

One of our test riders took second in the Intermediate class at a gnarly cross-country race on the bone-stock KX450F.

The KX450F is heavier than the other 450Fs, even the electric start KTM. It looks awesome when it’s brand new but the graphics and dark plastic age quickly, and the plastic itself is brittle and cracks easily. The 7/8-inch-diameter Renthal bars seem old fashioned, and the rubber handlebar mounts twist easily in the tripleclamps when you fall.

Our favorite things about the 2011 KX450F are its raw power, easy starting and resistance to stalling. The amount of raw power can help you make up lost time in the turns with a huge blast of throttle once the track straightens out. No wonder desert racers love these bikes! Fuel capacity is 1.9 gallons, and combined with EFI fuel efficiency the KX450F will go quite far on a tank of gas.

During our test Matt McCarthy raced his stock KX450F to second Intermediate at the Motopark Cross-Country and went almost two hours before needing more fuel! The new seat is firmer than in 2010, but is still relatively soft and has nice grippy sides. The suspension isn’t even too bad in the woods at race pace; if anything the fork is a bit too soft for motocross.

The KX450F has been proven to be able to win any race, any time. It feels a bit dated compared to the other 450s, but has great aftermarket support and fits bigger riders nicely. It’s strong too; Parker put over 60 hours on his practice bike and it was fine when he tore it down for inspection. With a few minor mods and suspension tuning we would be happy to have a KX450F for motocross. It might not be our first choice for singletrack races, but then again it wouldn’t be our last choice. But put the KX450F on a track with power-sapping uphills and long straights, and it becomes a very effective trophy-gathering tool.