Letter From Europe
LETTER FROM Europe
KTM's four-stroke: inhouse and light
Austria’s KTM factory is riding the crest of a sales and MX competition wave. With Heinz Kinigadner clinching the 1985 250cc World MX title for the second year in a row, and Danny “Magoo’’ Chandler teaming with Britain’s Kurt Nicoll to form the only consistent European challenge in the 500 MX class to the Japanese factories, KTM has become a giant-killer. This track success has been translated into rising sales of KTM’s high-quality off-road bikes. And according to sales chief Kalman Cseh, production for the current model year of 11,500 motorcycles, of which 95 percent are exported, is up 10 percent compared with 1983. Nearly 2600 of those machines were shipped to the U.S.
For the past few years, the company has been offering a four-stroke enduro model, fitted with a fourvalve, single-cylinder powerplant purchased from Rotax—the same engine that’s become the hot ticket in U.S. short-track events in recent times. But sales of these models have been declining (only 750 or so were built in 1984/1985), so KTM has decided to divert from its established policy of building only two-stroke engines by designing an in-house four-stroke Single, tentatively called the LC4, that will debut at the Cologne Show in the fall of 1986.
Three prototypes of the LC4 engine designed by 30-year old Fritz Wagner have already been built.
The liquid-cooled power unit is extremely compact and light, weighing only 73 pounds in prototype form with gearbox oil but no coolant. Development engineer Josef Hattinger expects the production version to scale a mere 64 pounds, which is scarcely heavier than the current KTM 500 two-stroke, and substantially less than the 97 pounds of the current Rotax unit. “Our main intention was to produce a much lighter and stronger engine than the Rotax,’’ says Wagner, “as well as reduce the overall dimensions so we can put the weight where we want to.’’
The LC4’s four valves are chaindriven, rather than belt-driven as on the Rotax, in the interests of a more compact engine. The roller-bearing crankshaft carries a forged Mahle piston running in a Nikasil cylinder that is designed to allow overboring, so a 600cc version eventually can be produced. Running on 9.8:1 compression with a 40mm Dell’Orto carburetor and a 2-into-l exhaust, the unit produces 48 bhp at 7800 rpm, with maximum torque at 6700 rpm. With a racing camshaft and higher compression, around 65 bhp is expected, comparing favorably with Magoo’s 1985 factory two-stroke, which yielded 68 bhp at the gearbox. The LC4 is safe to 10,000 rpm, and revs higher in race form.
A single prototype bike has already been built and is presently undergoing road tests in the Austrian Alps. Using a chrome-moly steel frame with alloy swingarm, the bike scales 249 pounds with lights, oil and water. According to Wagner, the MX version that KTM plans to launch first will weigh about 236 pounds. Either a 40mm Marzocchi fork or the “upside down’’ White Power front suspension will be fitted, with rear suspension by the same Dutch company. It will use disc brakes front and rear made by KTM, with Brembo calipers. Top speed of the machine at present has been clocked at 106 mph—not bad for a 500 Single in enduro trim.
Originally, KTM intended to use numerous components from its proven MX two-strokes on the LC4, but all that is now borrowed from the 500 GP bike are the gearbox and some clutch parts. For 1986, the factory KTM two-stroke racers will be fitted with Swedish SEM electronic ignition, which is also being used on the LC4. The bike also employs twin coolant radiators and a single oil cooler, all of which are hand made in aluminum at the KTM factory (which, incidentally, now supplies most other European bike manufacturers as well as several car-racing teams with these components).
Cseh claims that several other European companies approached KTM to collaborate on the engine, but were politely turned away. “We wanted to make a power unit without any compromises, that would be exactly as we wanted it to be rather than reflect the intentions of a committee,’’ he says. One of the companies in question apparently was Maico, now working on its own similar power unit—and its very first four-stroke. But the LC4 isn’t the first KTM with poppet valves: That honor goes to the 125cc dohc roadracer that won several Austrian championships. KTM is hoping that the LC4 will bring the company similar success.
CZ resurfaces
Dominant in motocross in the early Seventies, and long since left behind by the pace of Oriental and Western motocross development, CZ has appeared at recent European MX events with a pre-production prototype of its new ’86 250. The 226-pound CZ is equipped with a liquid-cooled engine, a Marzocchi front fork and a single-shock rear suspension that uses an Ohlins damper unit. The claimed output is 43.5 bhp for the 246cc engine, which uses reed-valve induction, a Dell’Orto carburetor and Motoplat ignition. This new CZ motocrosser is expected to be available early next year. —Alan Cathcart
