SEEKING PERSONAL HAPPINESS WITH THE 2010 KAWASAKI KX450F (THE BIG BOY BIKE OF MOTOCROSS):

On Jul 31, 2010 Last updated Mar 1, 2018

Readers often call the palatial MXA towers with questions. The queries range from the latest racer gossip to technical problems to bike setup tips. I hear it all. And, quite honestly, I revel in helping readers find solutions.

The most frequent question, however, doesn’t concern tires, helmets, race gas or suspension settings (although these are all popular subjects). Nor do quizzical callers want to know what James Stewart had for lunch (if you really want to know, follow him on Twitter). Instead, MXA is barraged with the following question: “If you had your pick, what bike would you choose?” My answer must sound like a broken record to my MXA compatriots (who don’t always agree). For my money, it doesn’t get any better than the Kawasaki KX450F. Merely cracking the throttle causes elation. Over the past three years, the KX450F has had the undeniable ability to put a smile on my face. And, for the most part, the bike has improved each successive year.

When the stock throttle grip needs to be replaced, buy an aluminum tube. There are two distinct reasons why.

(1) Save yourself the hassle (and potential hospital trip) from razor blading the vulcanized grip off the tube.

(2) An aluminum throttle tube is substantially stronger than the stocker.

Admittedly, the respective qualities of the Kawasaki KX450F aren’t all that impressive, but what is good is really good. High atop the good list is the engine. In my personal opinion, the KX450F has the best powerplant in the galaxy. It trumps the linear KTM 450SXF, the bottom-end snap of the Yamaha YZ450F and the midrange oomph of the Honda CRF450. The KX450F has no equal when it comes to horsepower. Put that in your exhaust pipe and smoke it.

Speaking of exhaust pipes, for most skill levels the KX450F powerplant can hold its own with its stock stainless steel pipe. Considering that titanium exhaust systems cost upwards of $1000, most riders can forget dropping Benjamins on something they don’t need. That’s money in the bank.

Speaking of exhaust pipes, for most skill levels the KX450F powerplant can hold its own with its stock stainless steel pipe. Considering that titanium exhaust systems cost upwards of $1000, most riders can forget dropping Benjamins on something they don’t need. That’s money in the bank.

By most standards, I’m rather tall. I won’t be drafted into the NBA anytime soon, but at 6 foot 1 inch, I’m taller than the majority of motocross racers. Thankfully, the Kawasaki KX450F is tailored to my height. It has an open cockpit that allows me to move around on the bike with ease. Compared to the cramped CRF450 and cab-forward YZ450F, the KX450F is instantly comfortable for me. In the hands of shorter riders, the ergonomics are too spaced out. For me, it’s form-fitting.

In 2006 through 2009, 22mm offset triple clamps were a necessity. For 2010 Kawasaki changed the head angle. It made enough of a difference that many MXA test riders were happy with the stock offset.

At 175 pounds, I’m too heavy for a 250 four-stroke. My riding style favors smoothness over aggressiveness. Hence, I’m at home on a 450. On a big bike, I can choose to be lazy (something that one cannot afford to be on a 250F). Yet, I don’t want my 450 to be as lazy as I am?I want spice out of the powerband. The KX450F engine is muy caliente.

I’m not naive?I’m an MXA test rider. I get to ride every bike ever made whenever I want, so I’m well aware that the 2010 Kawasaki KX450F isn’t the perfect bike. Far from it! There are some major bugaboos that Kawasaki’s engineers need to fix before the words “perfection” and “KX450F” are uttered in the same sentence. However, in the three years that I’ve selected the KX450F as my personal race bike, I’ve come to terms with its peccadilloes. In truth, I’ve compensated for its flaws with a potpourri of aftermarket parts, riding techniques and homegrown solutions that every KX450F owner should know about.

A glimpse into the past reveals a few Einsteinian moments that took place in my cranium. It all began with the 2008 KX450F?the first KX450F that I fell in love with (I never really liked the 2006 or 2007 KX450Fs). The powerband was unbelievable, and the suspension was decent, but it did require a few minor fixes to make it better. What did I do to maximize the potential of the 2008 Kawasaki KX450F? Read on.

(1) Triple clamps. In stock trim, the 24.5mm triple clamps made the front end tuck and stand up in corners (particularly from center-out). In short order, I switched to Pro Circuit’s 22mm offset triple clamps (www.procircuit.com). Pulling the offset back increased the trail, which helped the front tire track more accurately through the center of corners. Following the switch, I tinkered with different fork leg heights. It’s a matter of personal preference, but for most tracks I found that having the fork legs 5mm up in the top clamp was the sweet spot.

(2) Gearing. One of the major weaknesses on the 2006 through 2010 KX450Fs has been the wide-ratio gearbox. Kawasaki switched to a five-speed gearbox in 2007 after entering the 450 market with a pitiful four-speeder in 2006. However, instead of changing the ratios, Kawasaki just tacked on a high-speed, offroad-applicable fifth gear. That is like fixing an ugly chick with a hat. Since changing the gearbox was out of the question, I did the next feasible thing. I played with gearing options. On tighter tracks, I added two teeth to the rear sprocket so that second gear would come into play sooner, third would be closer to second, and fifth would be usable. On faster tracks, I added one tooth to the rear sprocket (and forgot about fifth).

(3) Shock linkage. Since its inception, the rear of the KX450F has wallowed. Under heavy acceleration the shock squats down, minimizing straight-line traction and shock damping. I replaced the stock linkage with a longer Pro Circuit link (www.procircuit.com). It effectively ramped up the rising rate, changed the initial part of the shock’s stroke, and lowered the overall height of the bike.

To prevent the KX450F radiator from spitting out fluid like a drunkard during a tongue twister, a high-pressure radiator cap is a must-have. It is a cost-effective solution to a potentially serious (and expensive) problem.

(4) Chain guide. As it sits (even on the 2010 model), the KX450F chain chews through the stock chain guide with ease. The only solution was to invest in a polyurethane chain guide. My choice has always been the TM Designworks unit (www.tmdesignworks.com).

(5) Tires. Many factors come into play when choosing tires. With that said, no one in their right mind should ever run a Dunlop D742F front tire. This tire has put me on my head more times than I care to remember, or even can remember. It’s junk. I’m not a fan of the wider 120 rear tire, either. As a rule, I opt for a Dunlop 756 front and 110-width 756 rear. Dunlop’s threat to drop these tires from their lineup seems stupid to me.

(6) Rear axle nut. Why does Kawasaki use an axle nut with a cotter pin running through it? Does Kawasaki’s legal department run the R&D department? I replaced the poorly designed axle nut/cotter pin combination with a Honda CRF450 self-locking nut.

(7) Preload ring. No bike makes it more difficult to access the shock preload ring than the KX450F. An Enzo Technica preload ring (www.enzoracing.com) allows me to get rid of the top locking ring and tighten the preload ring without having to mess with the top ring. It is a lifesaver.

I felt good about the changes I made to my 2008 Kawasaki KX450F, so when the 2009 was rolled into the MXA workshop, I was elated to see that it addressed a few of the problematic areas.

I felt good about the changes I made to my 2008 Kawasaki KX450F, so when the 2009 was rolled into the MXA workshop, I was elated to see that it addressed a few of the problematic areas. Kawasaki’s engineers redesigned virtually every part on the 2009 KX450F. From fuel injection to the aluminum chassis, the 2009 model received a facelift that Joan Rivers would be jealous of.

I was noticeably happier on the 2009 KX450F than the previous model. The new chassis seemed to improve the handling (revised fork offset, shock linkage, decreased frame weight and higher swingarm pivot). And, although MXA test riders try to be modest, we’d be remiss if we weren’t patting ourselves on the back. Why? Kawasaki took our 2008 KX450F test report to heart and addressed our complaints. It’s nice to have a voice that manufacturers listen to. But I still had issues, and even though the 2009 KX450F was touted as MXA’s 450 Shootout winner, the bike left me wanting. Again, I searched for solutions. This time the answers were easier to find, since Kawasaki’s engineers failed to fix several of the complaints voiced on the previous model.

(1) Fork offset. The 2009 model had a revised fork offset (from 24mm to 23mm). It was a baby step, but Kawasaki should have taken a leap. I went with Pro Circuit’s 22mm offset triple clamps (www.procircuit.com). Surprise! The decreased trail turned this boat of a bike into a fairly sharp-handling motocrosser.

(2) Shifting. For as long as I can remember, Kawasaki motocross bikes have been plagued by poor-shifting transmissions. Effectively shifting the KX450F requires a deliberate foot-to-shifter motion. Failing to do so often results in finding a false neutral. Not good.

(3) Gearing. Kawasaki stuck with their cheesy four-speed transmission with a fifth gear tacked on. The gap between first and second gear was too large, as was the gap between fourth and fifth gear. I added a tooth to the rear sprocket to close the gaps. It was a solution, but it led to another problem, which was…

(4) Chain guide. Adding an extra tooth to the rear sprocket kept obliterating the chain guide (which Kawasaki had redesigned in 2008). If you don’t switch to a TM Designworks guide (www.tmdesignworks.com), the chain will eat through the chain guide and eventually gnaw away at the top of the swingarm. It’s not a possibility?it’s an inevitability.

(5) Rear axle. You can lead a horse to water, but you can’t make him drink. This has been the case with the stinkin’ cotter pin/rear axle on the KX450F. Kawasaki’s engineers and lawyers need to convene and come up with a better way to keep the rear axle nut from falling off. Oh wait, I already found a solution. Dear Kawasaki, use a self-locking rear axle nut. Problem solved.

(6) Clutch. The powerful engine was too much for the soft clutch. Abusing the clutch yielded bluish, burned-out clutch plates that equated to nothing more than molten scrap metal. I replaced the clutch springs with stiffer coils from Pro Circuit (www.procircuit.com). They helped, but the clutch still had a tendency to slip after hard use. The 2009 engine was just too strong for the clutch.

(7) Other problematic areas. The KX450F always boiled over. I switched to a 1.6 high-pressure radiator cap. It did the trick. The stock graphics blew off in no time. Expect to replace them after a few rides. Keep a close eye on the bolts on the underside of the rear fender (up by the airbox). I ended up tightening all of the bolts every few rides. Eventually, I bought stock in Loctite. Speaking of plastic parts, the fork guards, front fender and radiator shrouds were thin and brittle. You’re always one roost away from ordering a new set of plastics. When that happens, invest in thicker UFO or Acerbis plastics. I swapped out the plastic throttle tube?not by choice, but by necessity. Kawasaki vulcanizes the stock throttle grip onto the tube. Forget about scraping the grip off. Instead, I switched to an aluminum throttle tube. Also, take that awful Dunlop D742 front tire off (use it for a tire swing or let your Rottweiler chew on it, but don’t keep it on your bike).

The chain can wear through the stock chain guide in four motos of riding. We switch to a hard polyurethane guide (like T.M. Designworks). While at it, invest in an aftermarket chain slider, or risk sawing a hole through the swingarm.

With 2008 and 2009 behind me, I was eager to read Kawasaki’s literature on the 2010 KX450F. I anticipated more remedial changes. Over Kawasaki’s storied history, the manufacturer has significantly updated its models about every three years (and true to the timeline, the 2010 model wasn’t a complete redesign). The 2010 received moderately small changes, and all the hubbub was focused on the all-new Yamaha YZ450F.

After nine months of racing my 2010 Kawasaki KX450F, I have mostly positive things to say about the bike. As always, the engine is its greatest attribute, but the handling and suspension have also improved since my particular fondness for the KX450F started three years ago. Also on the like list is the electronic fuel injection. It’s the best EFI-equipped bike, bar none.

Sadly, Kawasaki’s engineers are not paying close enough attention to my personal needs. Thus, the same issues that plagued the KX450F for the past few years are still there. Do I have to come to the factory and fix these things myself?

(1) Shifting. While shifting improved over previous models, failure to shift with a purpose often leads to a false neutral?which can lead to a serious groin injury. This isn’t good in a race situation.

(2) Gearbox. What’s the holdup on the gearbox? It was wrong in 2006 and it’s still wrong today. Kawasaki needs to drop-kick their antiquated gearbox for a close-ratio gearbox fit for a motocross track. Then I could forget toying with different sprocket combinations.

(3) Clutch. Kawasaki did add more friction material to the clutch plate fibers, but it wasn’t enough. The engine is still too powerful for the soft clutch. I find minor relief via stiffer Pro Circuit clutch springs (www.procircuit.com).

(4) Weight. The USS Enterprise’s anchor weighs less than the 2010 KX450F. It would be another thing if the bike felt agile in corners and in the air, but it reacts like a flying pig. Kawasaki’s engineers desperately need to shave weight off the bike. Actually, shave is the wrong word…hack would be more accurate.

(5) Front brake. If the KX450F lost weight, then the mushy front brake wouldn’t be such an issue.

(6) Other problematic areas. This will sound like a broken record, but here goes. Replace the rear axle nut, stop thermo-welding the grip to the throttle tube, use glue on the radiator graphics, put more plastic in the plastic parts, increase the radiator cap’s pressure and design a better chain guide.

The parts that I change on my personal 2010 Kawasaki KX450F ring up at the cash register for less than $750. That’s less than the cost of a titanium exhaust system (and the KX450F is so powerful that you don’t need to spend money on the engine). To my way of thinking, the KX450F powerband is so good that it is worth a little hassle to get the rest of the bike right.

On my wish list for the 2011 Kawasaki KX450F is a completely new transmission, better chain guide, stronger brakes, less brittle plastics, self-locking rear axle nut, beefed-up clutch, high-pressure radiator cap, longer-lasting graphics, a glued-on throttle grip, sleeker ergos and a lifetime membership in Jenny Craig. Even so, come 2011 I’ll probably bury the hatchet, toss aside my qualms, and fall in love with the KX450F all over again.