DÉJÀ VU: KTM 550SX TWO-STROKE FACTORY EDITION

On Oct 9, 2016 Last updated Oct 9, 2016

By John Basher

This past November MXA was offered the chance to test a KTM 550SX Factory Edition two-stroke. What, you don’t believe me? It’s true. Take a look at the February 2016 issue of MXA. Not a subscriber? Click here.

Oregon Motorcycle Adventures KTM dealer Jeff Moffet had the odd idea of stuffing a 1994 KTM 550 M/XC engine into a 2015-1/2 KTM 250SXF Factory Edition chassis. It had never been done before, but Moffet was up to the challenge. Generous funds and a bunch of hours spent fabricating and modifying later, the KTM 550SX two-stroke Factory Edition was born. Or, in Mary Shelley’s world, Frankenstein’s monster.

The blending of old and new was difficult. Tiginit Motorsports, a custom off-road fabrication shop in Medford, Oregon, take care of the fabrication work. They created a new frame cradle from the downtubes to the footpegs on the 250SXF-FE chassis. Then the swingarm pivot hole in the 550 M/XC engine had to be machined in order to accept for the larger 250SXF swingarm pivot bolt. Different motor mounts were also required.

That was step one. Next came the air induction system. Moffett shaved down the 550 airbox to create clearance for the exhaust pipe. A wedge was machined off the intake flange to move the carburetor out of harm’s way from the WP shock. And, given that the 550 engine was 22 years old, it didn’t use a hydraulic clutch. A new lever, cable and guides were installed for the cable-actuated system.

“THE KTM 550SX TWO-STROKE FACTORY EDITION DIDN’T LAST LONG IN THE HANDS OF MXA TEST RIDERS. UNFORTUNATELY, THE LEFT CRANK SEAL WENT, RESULTING IN SMOKE BILLOWING OUT OF THE SILENCER. A 22-YEAR-OLD SEAL WILL INEVITABLY GIVE UP THE GHOST. THEM’S THE BREAKS.”

The most difficult task of the bike build came in finding a way to turn the rear wheel around. The 1994 KTM 550 M/XC engine’s countershaft sprocket was on the right side of the bike, while the kickstarter was positioned on the left. Moffet had to turn the rear wheel around while keeping the 250SXF swingarm. Here’s what he did. (1) Jeff tapped into his extensive knowledge on KTMs and discovered that a rear brake system off a KTM LC4 640 adventure bike would work. The dated caliper design wasn’t on par with what the 250SXF offered, but it provided enough clearance for the countershaft sprocket. (2) A tab for the rear brake caliper on the left side of the swingarm was necessary. That tab came off the 1994 KTM 550 M/XC swingarm. Jeff also cut off the chain guide mounts for a sano finish. (3) The swingarm modification wasn’t complete without welding an aluminum bracket on the right side, which acted as a chain guide mount.

Another example of fabrication excellence, Moffet cut the reservoir off the Factory Edition shock to provide clearance for the intake system. He drilled, tapped and installed a steel-braided line from the shock to the reservoir, which was mounted remotely under the seat. Lastly, he swapped the EFI-equipped 250SXF gas tank for a two-stroke-friendly 2016 KTM 150SX tank with built-in petcock. The ’16 tank was necessary in order to fit the Factory Edition plastic scheme.

Frankenstein’s monster got a Joan Rivers-like facelift when Moffet decided to clean things up by having the frame powdercoated orange. He also had Scott White at Pacific Pipe Repair polish and work out the dents in the stock 550 M/XC pipe. JenFab Fabrication fit the pipe to an FMF Shorty silencer. And for some insane reason, Jeff had the cylinder ported for more power. As a result, the 550 M/XC belched 70 horsepower.

The KTM 550SX two-stroke Factory Edition didn’t last long in the hands of MXA test riders. Unfortunately, the left crank seal went, resulting in smoke billowing out of the silencer. A 22-year-old seal will inevitably give up the ghost. Them’s the breaks. It was too bad that it happened shortly after we started testing the rare bike. I can tell you that the 550SX was scary fast, hard to start, suffered from bouts of terrible vibration, and made you appreciate the exhilaration of riding something so unique.

If you’re looking to buy the KTM 550SX Factory Edition off Jeff Moffet, don’t bother. You’re too late. Jeff sold the bike a few months ago for an undisclosed amount of money. I’d be happy, just as long as the bike ended up in the garage of some passionate gear head. The bike belongs in a museum, but just like Frankenstein’s monster, a beast shouldn’t be stuck in a cage.