At the dawn of the 1980s, a myriad of manufacturers were experimenting with producing a competitive four-stroke motocrosser, though dethroning the mighty two-stroke was a major uphill battle. Quite a few marques put their faith in Rotax, who had then recently debuted an impressive 498cc four-stroke single. Seeing the potential of the half-liter thumper, KTM worked out a deal with the Austrian engine outfit to supply a massaged version of its power plants for a new four-stroke model. Built to KTM’s requested specifications, the Rotax mill received a slight bump in displacement from 498 to 504cc thanks to a 1.5mm stroke increase.
On top of the well sorted engine, the 504 boasted a generous amount of top-shelf components such as Magura controls, Brembo disc brakes, Marzocchi 43mm forks, and the company’s first generation “Pro Lever” rear monoshock which utilized a Fox Twin Clicker shock — the latter two of which both boasted nearly a foot in travel. The stock respiratory hardware was comprised of K&N filtered 36mm Bing carbs and SuperTrapp pipes, and Acerbis was called upon to produce the 504’s plastics.
In what appears to have been in effort to ensure positive publicity, KTM supposedly called on Dirt Bike Magazine in 1982 to assist the manufacturer in developing the four-stroker. Despite the 504 being a more-than-solid machine, its top-shelf price—costing over 1/3 more than Honda’s XR500 at $3,080 in 1984 (which translates to $7,600 in 2018) — meant it was out of your average rider’s price range.
This particular first year example is powered by a Ron Wood 560cc Rotax engine. Wood has been involved in the dirt racing scene since the early ’80s, and became a distributor for Rotax’s four-stroke engines for use in AMA races. Wood’s engines utilized an array of top-shelf internals and other parts, and were offered in 500, 560, 600, 660, and 676cc displacements. This example’s Wood Rotax power plant recently received a top-end rebuild and new timing belt. The bike could still use a little bit of work here and there, but in general is a pretty beautiful dirt bike.
You can find this 1984 KTM 504 MX for sale here on Craigslist in Olympia, Washington with a price of $3,895.