In my cranium, riding a 500cc two-stroke is like being strapped to a bomb that is ready to explode—you just don’t know when. The countdown starts when you rotate the crank to get the piston at top-dead center. Then, with a strong, swift kick, it ignites the fuel in the combustion chamber, setting the bomb’s timer in motion. That might be an exaggeration on my part, but I know I am not the only racer who thinks that big five-oh-ohs are ticking time bombs. I have lots of seat time on 500cc two-strokes. Most people just take one look at the massive jug and cringe. Even worse, the Kawasaki KX500 was hideous-looking 30 years ago, and it hasn’t aged like fine wine in the aesthetics department. The tall gas tank and wide rear fender are horrendous-looking. Worse yet, the deep roar and tingling vibration of the big-displacement engine make brave men draw back in fear. It is intimidating. 


I am not sure why 500cc smokers have such a bad reputation. Back in the late ’80s and ’90s, riders like Destry Abbott, Ty Davis and Danny Hamel raced 100-plus mph through the desert on them without a fuss. Plus, motocross rock stars such as Jeff Ward, Mike Kiedrowski and Mike LaRocco won AMA National Championships on them! 

When a 500cc two-stroke machine —Honda or Kawasaki—comes down the MXA pipeline for testing, there is always hesitation from the test riders, including myself. Don’t get me wrong, I have loved my time on every 500cc smoker I have ever swung a leg over (mostly because I got away unscathed). Every minute that goes by in the saddle, however, I feel that much closer to my imminent death. I believe that 500s are ticking time bombs, and all that it takes to make them go off is a mistake on my part. I am the detonator.

THE GEAR: Jersey: FXR Racing Revo, Pants: FXR Racing Revo, Helmet: 6D ATR-2, Goggles: FMF Vision Powercore, Boots: Sidi Crossfire 3SR.


Most of the good 500c two-strokes I have ridden have been packaged in their original equipment. The hardest 500s for me to appreciate have been shoehorned into new-age aluminum chassis. You would think the opposite would be true, but modern chassis were built for a purpose, and that purpose isn’t to have a 30-year-old smoker engine shoved in it. There is a lot that goes into building a good chassis. Much of that effort focuses on how the frame will react to the sudden power delivery. When that mixture is out of whack, odd things happen, and none of those oddities are good. The original Kawasaki KX500 chassis is more than outdated; it is archaic! Bolts fly out at regular intervals. The frame and subframe break, and the old dog gives you double vision from the vibration. And, it is no comfort knowing that the vibration smooths out once you hit the meat of the power when you are wide open in third gear. 

This brings us to the 1991 TMR/KX Guru Racing Kawasaki KX500 build. MXA test riders who are old enough to have raced KX500s when they were new always say, “I did my time on the CR500, KX500, YZ490 and KTM 500 back in the day. When you get an updated 1981 Maico 490, call me.” Worse yet, the young test riders don’t have enough two-stroke experience to know what they are signing up for. After the first big handful, they start riding the KX500 like meek mice and don’t stay out on the track for very long. So, I elected to test the TMR/KX Guru Racing Kawasaki KX500 to keep the rest of the MXA team out of harm’s way. In truth, I was the best man for the job anyway. How so? I no longer have the 150-pound physique that I had when racing Supercross a decade ago. With marriage, a wife, two kids and a time-consuming workload at MXA, I have a “dad bod.” I admit that big-displacement two-strokes handle better when the rider’s body weight matches the bike’s weight. So, I took out a million-dollar life-insurance policy and strapped myself to the ticking time bomb.

I laugh now, because I got all worked up over nothing. Don’t get me wrong, I was relieved the second my time testing the KX500 was over, but it went much smoother than I had anticipated. I actually put in an offer to buy the bike from KX Guru Racing, because the adrenaline-versus-risk ratio was off the charts. I didn’t even talk to my financial advisor (my wife) before making the offer. Looking back, I am glad they turned me down. They wanted more than double what I was willing to spend. Does $15,000 seem a bit steep for a 30-year-old bike? Maybe it hasn’t aged like fine wine, but it sure has appreciated in value.

Maybe it was worth the money, but it was just too rich for my blood. I know there was a lot of cold-hard cash dumped into building it, and the work was done by the right people. I have tested many 500cc machines that were massaged by KX Guru Racing. These guys know the ins and outs of the big two-strokes. They know how to fix the KX500’s flaws. Many of their solutions require using updated new-age parts. For example, KX Guru Racing modified the stock swingarm to accept a KX450 rear wheel and larger 240mm KX450 rear rotor. Up front, the entire brake system was updated with KX450 components.

The powerful engine was smoothed out by tricks that Tom Morgan learned over his years at Team Kawasaki.


For the suspension, KX Guru Racing machined new dog bones, spec’ed to Team Kawasaki’s 132.5mm length. The new links raised the rear of the bike 10mm to place more weight on the front end to aid in cornering and also reduce the rate of speed at which the rear shock travels through its stroke. This helps reduce the bucking effect of the rear.

For the front of the bike, they ditched the 1991 forks and bought 2011 KX450F forks off eBay that came with the entire front-brake assembly. Applied Racing built them hybrid triple clamps that accommodated the KX450F front-end swap while keeping the KX500’s 22mm offset. They also found a 1994 KX500 shock body that was more updated than the 1991 shock. Both the forks and shock were tuned by Race Tech.

The finer points of the KX Guru Racing KX500 are made obvious by a quick analysis of the clutch mods. There is a CNC-machined, two-piece clutch cover that allows easy access to the clutch plates. There is also a trick alloy piece that replaces the stock one-piece clutch arm with a two-piece splined billet arm with an additional 10mm of length to reduce the amount of force required to pull the clutch. The clutch cable’s 90-degree sleeve was straightened out to approximately 45 degrees to reduce clutch-pull effort.

Another KX Guru Racing trick was the KIPS (power valve) bolt modification. The factory KX500 exhaust valve drums sit over-rotated in their normal state, which results in the auxiliary exhaust ports being slightly open to eliminate that initial hesitation and make for a snappier throttle response.

As I mentioned earlier, the KX500 chassis breaks now and again. KX Guru took the 1991 frame and had it reinforced and strengthened in key locations with gussets copied from the old Team Green off-road days and a few gussets designed and placed by KX Guru Racing themselves. To keep the rider’s feet planted, custom footpeg mounts were machined so that KX450 Raptor footpegs could be mounted. The rear brake lever mount was also modified for strength and to utilize newer-style KX levers. 

For the engine, the most experienced KX500 engine tuner was charged with the task; Tom Morgan (TMR) took over this part of the build. Tom was Jeff Ward’s Factory Kawasaki mechanic when Jeff raced KX500s in the early ’90s. Tom started by re-balancing the crankshaft, porting the cylinder and modifying the head. The head also got a very cool and convenient compression release that not only aided in easier starting but reduced loads on the engine internals, which is good, because most KX500 parts are no longer available from Kawasaki.

The dated 1991 forks were replaced with 2011 KX450F forks tuned by Race Tech.


If you have ever started a KX500, you know it is no easy task. The kick-back can wrench your knee in an instant. It takes a certain technique to start these bikes, and that technique is unfortunately a lost art. TMR’s compression release was a leg-saver. With a push of a button, located on the head, I could start the bike without breaking a sweat. Once I revved the engine, my vision got distorted from the heavy vibration. I remember thinking to myself, “This is going to be interesting trying to ride with double vision.”

I started off at a snail’s pace and gradually got brave enough to twist the throttle to the stops. I was surprised I didn’t tense up. The power was incredibly smooth. My initial thought was, “Too smooth.” Where is the hit, the pizzazz, the punch, the bang? There wasn’t any! TMR had smoothed out the power to build a ridable KX500 engine. As much as I was waiting for the type of power that scares you a little bit, it was nice to not have to hang on for dear life. The faster I went, the less the engine vibrated, which allowed my vision to come back into focus. The Tom Morgan KX500 engine loved to be short-shifted and ridden in the middle of the powerband. It had a gentle grunt that allowed you to ride a gear high. With its sheer power, I could be lazy and keep it in third pretty much the entire Glen Helen track, save for the long start straight.

It took some time to feel comfortable jumping the bike due to a few bad experiences of getting bucked off in the past. My previous KX500 experiences included many sets of mismatched suspension components. Thankfully, Race Tech did an amazing job balancing out this version’s suspension. The front and rear worked in unison, and I felt I could hit any kicker, square edge or jump without concern.

Most of the weight of the KX500 is on the front of the bike. When you take the bike off the stand, it feels light in the rear. I mention this because one of my favorite things about riding KX500s is their ability to step the rear end out with a blip of the throttle and flat track around corners. Mixing this handling trait with good suspension made the KX Guru Racing KX500 a blast to ride. It was honestly like riding a couch on wheels. I am not claiming that it wasn’t a little scary, even with its mellow power delivery, but it was the least scary 500cc two-stroke I have ever ridden.

After each riding session, I came back with something missing—mostly bolts, but every now and then some plastic parts. I expected that and was prepared for the inevitable. The bike was incredibly fun and easy to ride—for a 500cc machine. The power had no dips or valleys and had a very connected feel at all times. I always felt like I was going slower than I actually was, but the lack of engine braking heading into corners made me realize how fast I was going in reality. 

Overall, the KX Guru Racing KX500 was by far the most user-friendly 500cc two-stroke I have ever ridden. The power was manageable and smooth, and the suspension was super plush. The integration of new-age technology, years of experience from KX500 racing, and Race Tech’s suspension expertise brought this old dog into the current decade. It was an amazing bike for what it was, and I wanted it in my garage. But, I will admit I wanted it more as a trophy than a bike I would ride on a regular basis. It would be a bike I would sit and stare at—a bike that I would only ride on those rare occasions when I felt like strapping myself to a bomb to see what would happen. Guess what? I can still drop by KX Guru Racing and look at it without spending $15,000.


KX Guru Racing: http://oem-cycle.com/forum/index.php

Applied Racing: www.appliedrace.com  

TMR: www.tommorganracing1.com

FMF Racing: www.fmfracing.com 

P3 Carbon: www.p3carbon.com

Cometic Gasket: www.cometic.com

Galfer USA: www.galferusa.com

Supersprox: www.supersproxusa.com  

Wossner Pistons: www.wossnerpistons.com

Faster USA: www.fasterusa.com

Pivot Works: www.pivotworks.com

Dunlop Tire: www.dunlopmotorcycle.com 

All Balls: www.allballsracing.com

Hinson Clutch Components: www.hinsonracing.com    

Race Tech: www.racetech.com      

Uni Filter: www.unifilter.com 

UFO Plastic: www.ufoplasticusa.com

Works Connection: www.worksconnection.com 

DeCal Works: www.decalmx.com 

Raptor: www.raptortitanium.com 

Moto Tassinari: www.mototassinari.com   

ICW: www.icwbikestands.com 

San Diego Powder Coating: www.sandiegopowdercoating.com 

Moto Seat: www.motoseat.com  

Fasst Co.: www.fasstco.com

Specbolt Fasteners: www.specbolt.com 

VP Fuel: www.vpracingfuels.com 

ODI: www.odigrips.com

Motoblasters: www.motoblasters.com

Nihilo Concepts: www.nihiloconcepts.com

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