1996 Polaris Indy 650 Triple Rxl Specs Free Air Triples

Jerry Shank was the lead engine developer at the time and tells us the triples were supplied originally with Tillotson carbs until they were able to solve a fuel foaming problem with the Mikuni carbs.

The 120-degree firing sequence of a triple is sexy and very addictive.

For many snowmobilers there is no better sound on the planet than that of a triple-piped three-cylinder two-stroke engine singing at high rpm levels.

Memories of sleds like the SRX, Mach Z, XCR 800 and ZRT should make us all smile.

The demise of the triple-cylinder two-stroke continues to puzzle for many of us and this story will look at the origins right through to the end when a host of changes in the snowmobile business silenced what many call The National Anthem of Snowmobiling.

Everyone in the snow belt was buying one or seriously thinking about it.

People bought a single-cylinder 12hp sled and once they became more comfortable with riding a machine in the snow they typically opted for a sled with more power.

The birth of the twin cylinder 340,400 and 440cc engines soon followed for production snowmobiles.

The summer of 1968 at the annual USSA (United States Snowmobile Association) rules meetings had on the top of the agenda a call to put a limit on engine size.

The horsepower race was getting out of hand, it was concluded (sound familiar).

That would change for the 1970 season when Polaris introduced their Star engine built exclusively for Polaris by Fuji Heavy Industries (Subaru).

1996 Polaris Indy 650 Triple Rxl Specs Free Air Triples

Polaris would race their new 649 and 795cc free air triples combined with their new aluminum flyweight clutch to many race victories.

Arctic Cat was just beginning to develop an alliance with Kawasaki, which was chomping at the bit to enter the snowmobile market.

Kawasaki had already released their three-cylinder free air street bikes which were real fast and Arctic Cat wanted that power in their race sleds.

Ski-doo introduced their new Blizzard race sleds in 1970 with 636 and 776cc twins.

Ski-doo had a successful season in 1970 but the writing was on the wall.

The horsepower war was ramping up and to compete with the Honker motors Rotax would up the anti in 1971 with new free air 645 and 797cc tripletriples.

The new Ski-doo triple-cylinder Blizzards were built on a wider tunnel using a 16.5 wide track vs.

The 71 Blizzard had these big triples sitting right there in your lap with the motor mounted on top of the tunnel.

The 645 featured a 67mm bore putting out 71 hp and the big 797 was a punched out version with a 74.5mm bore putting out 88 hp.

The over-square triples (bore diameter larger than stroke length) could now rev higher and that typically meant more peak HP.

The tradeoff was less torque (bottom end) with the shorter stroke motor.