1968 Polaris TX-500
This sled wanted to be first!
In the late 1960s, Polaris set out to make a high-performance snowmobile with even more speed and excitement. The president of Polaris was Allan Hetteen, and he loved to make Polaris snowmobiles race and win. He knew that when you win races, word gets out about your snowmobiles.
Polaris came up with the TX-500, named after the Winnipeg 500 cross country race. Whoever won that race earned bragging rights for how fast and durable their brand of snowmobile was, and it helped sales too!
The TX-500 came with four different engine options. The most popular was a single-cylinder, German-made engine called the JLO that was modified from 372cc to 396cc. It came with an expansion chamber (tuned pipe) for more power, and it was a better running engine.
Another engine option was a JLO twin-cylinder 594cc “opposed” (laid down) engine with one spark plug to the front and one to the rear of the engine bay. This left no room for expansion chambers, so Polaris ran straight pipes out the belly pan. This engine had twin HD Tillotson carburetors on top. The engine weighed close to 95 lbs., and since it wasn’t as powerful as the TX-500, it was not the preferred race engine.
Engine option three was a German Hirth twin-cylinder upright inline 600cc with dual carbs. Cast iron cylinders brought the engine’s weight to 85 lbs., which was still heavy for the 30-35 hp that it put out. The exhaust had curved twin straight pipes run right out of the belly pan. It was loud and rumbling!
Option four was a JLO 744cc inline twin, available for racers. It was hand-built from a JLO 384cc twin crankcase engine. Cylinders were bored out to 100 thousandths over, becoming a 792cc for the 800cc mod class. It had cast aluminum brake and throttle levers (with a steel flipper) for more durability.
Polaris also redesigned their Torque-O-Matic clutch to handle more torque and higher engine RPMs of the race engines. The drive clutch was beefed up and more weight installed. Polaris then used a larger driven clutch than its standard 9-inch. The use of an 11-inch driven meant that the OEM had to make a taller chaincase.
To solve that problem, Polaris made a cast aluminum chaincase with an easily removable cover for sprocket or chain replacement. A double #35 chain and sprockets gave it greater strength and durability. This chaincase was only used on the 1968 TX-500 model. The 1969 models used a refined aluminum chaincase with the 11-inch driven clutch.
A larger fuel tank was mounted on the rear of the sled for easy fueling. Going from a 3-gallon side tank to a 5-gallon rear tank made a lot of difference. To give it a sportier look, Polaris added a nice red plastic cover and a wraparound bumper.
Two track options were a 15-inch-wide center drive all-rubber track, or one with 37 “cleats” on it. There also was a new bogey wheel system that held the wheels in place so they wouldn’t flip over when racing. This system was not as fast as Arctic Cat’s slide rail suspension, so in 1969 Polaris starting trying slide rails out.
Suspension springs on the rear axle gave three inches of travel, which was surprisingly good for its time. A six-inch-high soft seat helped cushion the bumps, but riders sure flew through the air on some of those cross country races!
Photos of this TX-500 show a hood with a large grill opening to provide more air for cooling. I was told Polaris engineers used aluminum from the local Roseau hardware store for these hoods.
I think it looks great! This new type of grill helped cool the engines, which were prone to overheating. Polaris liked it enough to use it on their regular models in 1969.
Thanks to Dave Larson for sharing his beautiful Polaris TX-500 with us!
Minnesotan Les Pinz is a vintage sled expert with an extensive collection of historic and other antique sleds, and is a former snowmobile racer. He is a member of the International Snowmobile Hall of Fame and one of AmSnow’s regular test riders.