Back when men were men and motocross bikes were faster than they needed to be, 500cc two-strokes ruled the roost-no pun intended. In the heyday of motocross, names like Jeff Stanton, Ricky Johnson, Mike Kiedrowski, and Mike LaRaocco were the stars aboard these blistering fast machines, competing for the once coveted 500cc National Championship. Since then, however, times have changed, as four-strokes have rapidly become the dominating machines in both professional and amateur competition around the world.

Due to the simple fact that the new four-stroke technology has taken over, two-strokes have gone the way the way of the Dodo for most manufacturers, and to quite a few riders, are all but forgotten memories of motocross’ past. Thankfully, though, for all the diehard premix fans out there who want to go ridiculously fast, Service Honda has come to the rescue with the new Service Kawasaki KX500AF. Packing quite a punch, and squeezed into a 2009 KX250F frame, the KX500AF is without a doubt, an interesting bike.

Brendan Lutes on the KX500AF.

THE BIKE
Service Honda has long been know for… you guessed it, squeezing Honda CR500R motors into modern aluminum framed chassis, but up until this year, the company hasn’t ventured into producing a bike based on the KX500.

Through a special agreement with Kawasaki, Service Honda uses brand-new components to build each KX500AF. To begin the project, Service Honda takes a stock KX250F and strips it down, cutting the frame and welding new down spars in place to hold the powerful KX500 motor. From there, the motor is slipped in while all the necessary components are mounted up to complete the bike. When everything is said and done, the KX500 motor fits flawlessly into the KX250F chassis. A few of the custom features that make up the KX500AF include custom front airbox plate for optimum airflow along with a new airboot, a stainless steel clutch cable for increased life. a works-style aluminum skid plate, and a 39mm Keihin PWK carburetor to feed the motor.

As far as suspension is concerned. Service Honda recommends getting it revalved by MX Tech Suspension in order to handle the new characteristics of the powerful KX500AF. When we took delivery of our test bike, the first thing we did was mount  up massaged suspension-although from Pro Action rather than MX Tech-off of our KX250F test bike, giving the 500 the highly recommended upgrade. Other than that, our KX500AF was left largely untouched from the condition and setup that it was delivered to us in.

OUT ON THE TRACK
The Service Kawasaki KX500AF is a very powerful bike that demands respect from anyone that swings a leg over it-the power is instantaneous and awesome. Out on the track, the low-end grunt is something that one has to feel to believe, and once the throttle is cracked, it comes on strong, pulling very hard into the upper portion of the powerband. It pulled so far that even on fast tracks we struggled to find where the power signed off. Compared to other two-strokes we have ridden in the past, the 500 has more of a tractor-like powerband. While the power is very strong, it is strong in a different way, allowing some control over what most would think to be an uncontrollable experience. On the other hand, though, this power can be deceiving, as it builds up and continues to pull forever.

We haven’t ridden an original KX500 since, well…. we don’t remember, so it’s kind of difficult to comment on the vibration of the Service bike compared to the old chassis, however we can say that the vibration of the KX500AF isn’t bad. While it does vibrate a little more than a four-stroke, it isn’t enough to make for an unpleasant ride, but rather enough to wear you out quicker than normal. The 500 is a potent bike, and because of that, it’s going to wear the rider out a little more. Having said that, however the Service bike is much more nimble than we had expected before riding it. The lightweight 250F chassis provides a very modern feel to the ride, while working well with the powerful 500cc engine, giving the bike a controllable feel despite the big motor. As for the suspension, we swapped out the stock suspension in favor of Pro Action suspension and the end result was excellent.

The bike never felt nervous at speed down straights, and was very confidence-inspiring over jumps. As for smaller hits-braking bumps and acceleration bumps-the forks and shock worked very well to keep the bike riding straight. Simply put, if you like the handling characteristics of the KX250F, you’re going to like the way the KX500AF handles after a little suspension tuning.

WHAT WE THINK
Our time aboard the big green Service Kawasaki KX500AF was a blast. Before riding it, we had our questions about whether or not it would perform up to par, but after testing it in races and at various local tracks, we have come away surprised with how well it works as a complete package. One thing is for sure though, in spite of the new chassis and ergonomics, the KX500AF remains  a true “man’s” bike, as the brute power is something that can’t be taken lightly, not to mention holding on for an extended period of time requires more training for the truly dedicated. For everyone else, it’s a lot of fun no matter what.

By Brendan Lutes
Up until the time when the Service Kawaski KX500AF arrived at our offices, I had only swung a leg over a 500cc two-stroke once in my life. I always thought that the fabled bikes of yesteryear would be way too much to handle for anyone, and that for me, I wouldn’t be able to ride to my full potential. I couldn’t have been more wrong.

After getting used to the KX500AF and pounding out a few motos, I became aware that although the big bike commanded a lot of respect, it was a bike that was very fun to ride. The instant power allowed me to ride around the track and be lazy-I’m not sure if that’s a good thing or not-and the lightweight chassis that the motor was placed into gave the bike a feeling reminiscent of the modern four-strokes I have become accustomed to. While I did get tired much quicker, it wasn’t something that I couldn’t overcome with a little more seat time aboard the big bike, or a little more time at the gym rather than my favorite watering hole. In fact, since taking delivery of the KX500AF, I’ve even raced it and had a blast. But riding motos on it is one thing; where the test really got interesting for me was when we broke out the stopwatch.

After being timed aboard the big KX500AF at Racetown 395, I hoped on my more familiar KX450F and immediately felt right at home. While pounding out timed laps, I clearly remember thinking to myself, “Man, I’m killing the lap times I set on the 500!. Upon pulling back into the pits, however, I found that I couldn’t have been further from the truth. While I felt faster and more at home on the 450, my lap times on the 500 were consistently two to three seconds a lap faster. In the end, the truth of the matter was that the brute power of the 500 undoubtedly allowed me to carry more speed down the straights and through the corners-even if it didn’t feel like it-giving the big bike that little edge over the 450. Even though the lap times speak for themselves, under race conditions, and on a rough track, I would probably pick the 450 over the 500. I’m more comfortable on the 450, and I can ride it at a consistent pace for a longer period of time. Nonetheless, I still had a blast during my time testing the 500. It’s definitely something different and fun.