Vintage racing has become the surprise hit of the snowmobile world. Heck, it may be the fastest growing form of snowmobile racing today.
From a modest beginning only a few years ago, participation at the Eagle River Vintage World Championship oval races had more than 500 entries last year. Starting as just a small part of the oval show, the vintage racers now have a full weekend of racing the week before the traditional race. Plus they still help fill in the program on Derby weekend.
Part of vintage racing's attraction is the relatively few rules, particularly in the Open classes, and the fact that new technology is limited to the inventiveness of the participants. Without the threat of being outdated by new factory equipment, the competition is fierce among those who take this sport seriously. With 20/20 hindsight, racers find interesting ways to improve existing components.
In the Open class, you can race anything made before 1980, and classes are usually separated into free air and liquid-cooled models. History lessons are everywhere, as early brands are reborn into new glory.
The chance to see some serious racing machinery from the 1970's "Golden Age" in action brings back nostalgic memories to veterans, and sparks amazement among the younger crowd.
So it wasn't too surprising a few years ago that a buzz of excitement was stirred by rumors of an exceptionally quick rotary racer based on the Johnson Rotary engine.
Johnson/Evinrude produced the Wankel-powered machines for several seasons - not as a racer, but as a 45-horsepower large luxury trail cruiser with a 20-inch track, electric start, reverse and a cigarette lighter.
OMC's advanced engineering department made a lightweight racer with the engine modified to create 60 hp to test its feasibility for racing. Although the torque was impressive, and might have been suitable for snocross, the lack of horsepower made it unsuitable for the Open class it was destined to run in.
Back then the competition ran 100 hp triples, and no matter how much torque you had, exiting corners with a 40 hp deficit meant you'd be left behind on the straights. As a result, the single rotary Wankel racing project was shelved. Despite this mothballing, the outboard division went on to make some four-rotor monsters that dominated the big outboard racing class at the time.
Fast Forward to New Projects
Fast-forward 25 years and today we focus on three racing enthusiasts who like to meet for a beer in the garage on Thursday nights and dream up new sled projects. Roger Buermann, Pete Krueger and Kelly Renken dreamed up the twin rotary racers in Roger's garage during one of these sessions.
Roger owned and rode Johnson snowmobiles long after production ceased, and in the process of finding parts for his hobby, he bought out parts from dealers and other collectors. That inventory included a fair number of rotary engines, which spurred the group's idea to couple two of them together.
Roger and his buddies wanted to begin vintage racing, but also wanted to create something radical and different that could make its own history rather than simply be a replica of a factory racing sled.
Since Johnson had no snowmobile racing history with the rotary, except for the experimental machine that had never been raced, anything they did with the rotary engine would be unique and fully legal in the Open class. Open class racing in the '70s had seen plenty of triples and even fours welded together from twin parts, so there could be no objection to combining a couple of rotary engines.
A 45-hp rotary could be coaxed to deliver at least 50 hp with some porting. Throwing away the fan and shrouding to make it a free air machine also would likely free up more power. With a potential of more than 100 hp, the project sled looked like it could be competitive with the 440 and 650 engines of that period. However, theory is one thing, doing it is a different story.
In this case, Roger had plenty of parts and the three partners attacked the project with enthusiasm and a good ol' hot rod mentality. The original Johnson rotary engine is charge cooled, which means the fuel mix is sucked through passages in the inside of the steel rotor, both to cool it and lubricate the rotor bearings.
From there, the charge is sucked into the rotor housing where it gets compressed, burned and exhausted as it follows the rotor around.
The Wankel engine basically works on 4-stroke principles, but fires once per crankshaft revolution, just like a 2-stroke piston engine. Coupling two rotors together would therefore make it work like a 2-stroke twin, except that the rotary produces more low-end torque because of its 4-stroke-like positive displacement during the intake cycle.
A large fan shrouding and hand starter dominate the stock engine's right side, while the ignition is covered by a large flywheel on the output side, which also acts as the stationary clutch sheave. Both the ignition system and the fan with its shrouding was stripped off the rotor housing, and only the housing and the side plates with the cooling fins were left with a shaft sticking out each end. The rotor shafts are relatively large and were made hollow to save weight.
"Team Johnson" took advantage of this by machining the center hole and coupling the two shafts together with an inside shaft. The inside shaft was then fastened to the rotor shafts with "thru" pins. The two shafts were mounted 180 degrees to each other, giving two equally spaced power pulses per revolution. On the power takeoff side, a tapered shaft for a Comet clutch was threaded into the hollow rotor shaft. A starter cup and the ignition pick-ups were located on the outside of the right side rotor housing. Ignition is by battery and a Mallory automotive ignition using Accel Super Coils.
The whole assembly is rotated so the exhaust port points straight down, and a couple of 3-inch stubs shoot the exhaust down onto the ice. They did this on purpose to let the exhaust in turn throw ice and snow dust directly on the cooling fins. Cooling air enters on the bottom because there is no pan and hits directly on the hot parts of the housing that contains the combustion chambers.
Spark plugs for the rotary engines are no longer available, but they solved that problem by using a marine plug with longer reach and then spacing it back with a thicker washer. With the engine tilted, the regular float bowl carbs couldn't be used, so a set of Tillotson HD carbs from a 650-twin model was used. This worked amazingly well, as the carbs tuned right in with only small adjustments.
The chassis uses the original tunnel from a Johnson Rampage snowmobile, with a cleated track on a racing slide rail suspension. In front, an aluminum bulkhead sandwiches the two rotor housings and extends to the crossbar and ski spindles in front. It mounts to the tunnel with the secondary shaft, chain case and drive shaft.
A small, modified Rampage hood completes the sled's front. With the twin rotor engine installed the sled weighs only 300 lbs. Originally, the engine had a hand start unit, but the rotary is hard to start when cold and the snowmobile version had electric start. To overcome the problem, Team Johnson uses an Indy Car-style remote starter mounted on a battery cart that is put into the starter coupling to crank the engine over for starting.
Starting the engine is quite dramatic, as flames shoot out the short exhaust stacks. When they hit the ice steam blows out from under the machine, making the bystanders think the whole thing is on fire. The sound from the short stacks rivals that of a megaphone equipped 2-stroke engine.
A project like this could well have ended up in a twisted heap of junk parts, but not this sled. The solutions were well thought out and the parts machining was exceptionally high quality. Both Roger and Pete have automotive backgrounds, with long experience in fabricating parts and they have access to the necessary machine shop equipment.
Kelly is the driver, and the project has been successful beyond expectations. In all, the machine has won three classes at the Eagle River Vintage World Championships, two in free air and one in liquid. In addition, it has won numerous local oval and drag races. The strongest aspect of this sled is its impressive acceleration out of turns due to the twin rotary's massive torque.
Naturally the engine attracts a lot of attention when Team Johnson shows up anywhere. Competition in the Open class is now getting very stiff with 800cc, 140-hp free air triples. In addition the light chassis does not handle as well as the factory-based Polaris Starfire sleds.
So the group is working on plans for the sled to bow out of oval racing to concentrate on drags. Exotic fuel mixes of alcohol and nitro also are being discussed at Thursday night bench racing sessions.
The Team Johnson boys have not given up on oval racing, but the focus is turning toward the 2-stroke parts from the inventory bin. Exactly what the new creation will be is a secret, for now. You can be assured that Team Johnson is thinking outside the box, so count on something radical.
Team Johnson is not alone in its quest for the perfect vintage sled. Racers all over North America are having bench racing sessions and dreaming up new and improved applications for old parts. If you like to see technically interesting sleds, check out the fast growing vintage scene next time there's an event in your neck of the woods.
Olav Aaen is a long-time contributor to the snowmobile industry. As a mechanical engineer and president of Aaen Performance, Olav has been heavily involved with snowmobile performance since 1968. Aaen Performance is best known for pioneering performance pipes and introducing the roller clutch to the snowmobile marketplace.
This story appeared in the January 2005 issue of American Snowmobiler magazine