KX500/KTM 350XC-F Project Beast

Excuse me? Did you just say a KX 500 and a KTM 350XC-F rolled into one? Yes, that’s correct; Jonny Weisman of TBT Racing Arizona blended both motorcycles together for an incredibly beautiful piece of machinery. Jonny took an old 2002 KX500 engine that he had lying around and mounted it in a 2014 KTM 350XC-F. Both bikes were being un-used in his shop, so he decided to create a 500cc two-stroke that implemented modern day chassis/suspension technology and the KX500/KTM 350XC-F was born. Tons of labor went into Jonny’s project as he was focused on making a clean almost un-modified looking machine. We had the pleasure of riding this unique beast at a local top-secret sand track in Southern California and this is what we came away with.

TBT has KYB conversion kits that can go into your WP 4CS or AER fork. Having the KYB internals really settled the front end down when coming in hard into braking bumps.Photo by Preston Jordan

First let’s start with how Jonny Weisman got to this point and what he had to do to mate the Kawasaki engine to the KTM chassis. Over 70 man-hours of labor were involved to create such a bike as he had to bore the swingarm pivot hole in the cases to accept the KTM pivot bolt. He then cut out all of the original engine mounts, which actually all lined up pretty close, but were just a tad too short, the head stay mounts, which are actually the stock KTM 350 XC-F mounts were modified a little to fit, the intake boot was switched to a KTM 250 SX design and then modified to get the correct length, the Scalvini pipe took a lot of work to make fit as it was designed for a Honda CR500AF, it came with no mounts because Jonny wanted to custom build his own mounts to fit properly with the Kawasaki’s engine and KTM mounting points, clearing and angling the pipe to make room for the front tire, kick-starter, and cylinder water fitting were tricky and took some patience on his part, the Scalvini silencer was also modified to fit, to get the correct angle to the pipe as well, the radiators were fully welded to add strength and protect against leaks, the suspension is also unique as the fork incorporates KYB inners and WP outer tubes, and finally the fork legs received the full treatment of Kashima coatings and out back the shock is a standard WP unit with it being valved for motocross use.

Scalvini sent a cone pipe, but Jonny Weisman had to heavily modify the pipe in able to make it fit correctly onto the KTM chassis.Photo by Preston Jordan

The minute we started the KX500 we knew we were in for a special treat. At first we had to re-train ourselves on how to start a 500 properly, but once we got it down the KX500 was easy to get fired up. Revving the engine is also a very foreign feeling to the arms. As much as the FAAST bars helped with vibration it was more than we remember in quite sometime. Once clicked into gear and the throttle was opened our smiles never seem to diminish. We were expecting a violent bottom end hit, but instead we go a very friendly, tractable power delivery. Out of corners the KX 500’s engine was smooth and predictable with great rear wheel traction. This engine doesn’t have a real hit to it down low like a 450cc’d four-stroke, instead it chugs along smoother and can be lugged as good if not better than any motocross four-stroke on the market today. Mid-range power is where you’ll need to start holding on tight and gripping with your legs. Second and third gears are very useable with the big two-stroke. For a bigger size engine the 500 can rev-out fairly well. Case in point, we took a new Honda CRF450RX and the TBT Racing 500 two-stroke and dragged raced them down a fire road and the 500 pulled the Honda slightly by the end of the half-mile. Only at the very end of the long straight was the KX500 able to start creeping away from the Honda four-stroke.

When you have as much horsepower as this KX500 engine has getting this sucker to brake is a must. A Flo oversize 270mm front rotor was installed to ensure that we didn’t blow any corners.Photo by Preston Jordan

The chassis and suspension on the older Kawasaki 500’s were decent in their day, but compared to today’s standards, is sub-par. Putting the Kawi’s engine in a KTM 350 XC-F chassis along with a set of updated suspension, really let us ride the machine to its full capabilities. Once out on the track and trails we immediately noticed how well the fork action was of the TBT Hybrid 500 two-stroke. The KYB internals from the SSS fork found on current Yamahas made the front end of the 500 feel more planted and didn’t have that mushy feeling that the old set of Kawasaki forks would have. Over small, rough, choppy sections of the track we tested at the KYB fork has a great feel and plenty of damping to keep the big two-stroke from pitching on de-cel. Having a WP rear shock, we were skeptical and thought that the mighty 500 would feel unbalanced on the track, but the rear felt comfortable on acceleration and gave us a good amount of rear wheel traction under load. We had to stiffen the shock up a few clicks to prevent it from bottoming on g-outs, but overall the whole bike felt balanced and had that late model feel to it.

Ride Engineering provided the 22mm offset clamps that didn’t increase rigidity feeling and gave the bike a trick look with its bright orange color.Photo by Preston Jordan

The chassis of the KTM 350XC-F helps the 500 to corner a little better, but don’t expect to be carving inside lines like you would on a Honda or Suzuki. Its straight-line stability is better than its cornering capability, but for the area we tested at (very sandy with big bowl turns) it was a blast to twist the throttle on. Ergonomics were a lot better as the seat, peg, handlebar ratio was a flatter feel and made us sit on top versus inside like the older Kawasaki 500’s had. For having a 15-year-old engine it’s amazing how easy it is to ride and how much fun you can have on a big bore two-stroke. The newer KTM chassis helps this tremendously when riding a rough motocross track or when the trail gets hacked out. This was a very fun experience and let us reminisce and respect all of the men who rode these beasts back in the day that much more. Look for a more in depth, very fun video with our test rider Gary Sutherlin coming to dirtrider.com shortly.

The FAAST Flexx handlebars really save the arms when it comes to the KX 500’s vibration. We couldn’t imagine not having a pair of rubber-mounted handlebars on something as gnarly as an open class two-stroke.Photo by Preston Jordan
Parts List:
Ride Engineering Clamps 22mm offset
GPR V4 Stabilizer
Fasst Flexx Bars
Fasst Impact Moto Peg
Flo Front Oversize Rotor Kit
Dunlop MX3S tires
Rental Chain, Sprockets and Kevlar Grips
ARC Memlon Levers
Magura Hydraulic Clutch Kit
Hinson Clutch Arm
Rekluse clutch cover
Hot rods Connecting Rod
TM Designs Chain Slider and Guide
Zip Ty Racing Shark Fin and Wheel Spacers
Cylinder port work (clean up), head cutting done by TBT Racing Arizona | 
Cylinder Re-plated
Seat Concepts Custom Complete Seat
Rad Custom Designs Graphics
Scalvini Heavily Modified Pipe
Scalvini Carbon Tip Silencer
Boyesen Rad Valve, Stator Cover
A GPR stabilizer was neatly tucked away under the FAAST handlebars for the high-speed trails. This is a standard issue piece when it comes to 500cc two-strokes. Trust us!Photo by Preston Jordan
The mighty 2002 KX500 powerplant. We were blown away on how easy it was to ride this very fast engine character. It rolled on buttery smooth, but pulls extremely hard through the mid-top end range. Only some mild headwork was done to the engine, otherwise she was completely stock.Photo by Preston Jordan
Test rider Gary Sutherlin had a great time for Preston’s camera. Gary commented that the weight of the 500 was not an issue and that it behaved well in the air.Photo by Preston Jordan
Lofting the front wheel up and over whoops was not an issue with the TBT Racing 500 two-stroke.Photo by Preston Jordan
In honor of Destry Abbott, Jonny Weisman (Destry’s ex-mechanic when he rode for Kawasaki) used the number 8 as a tip of the hat to his long time friend and cancer survivor.Photo by Preston Jordan
The KX500/KTM350 hybrid two-stroke is a thing of beauty.Photo by Preston Jordan