Originally Posted by ktmbmk66
Gunna have to vote for the polaris tx's as they were very tuff lil engines and higher tech than the doo's and on par with the cats but the tx's were lighter than the cats. I i do belive cats had a couple horses on the tx's due to their cyl. porting. But the tx is hard to kill.
I remember Popular Science did an article in 1972 where it torn down snowmobile engine to look at how well they were designed.
They said the Fuji engine was the most rugged, "big, husky, beautifully build engine."
The Kawasaki was a light engine, but it had chromed cylinders and people were able to get a lot of hp from them.
They said the american designed motors were the most innovative. Both Mercury's Kiekhaefer and OMC had float carbs, while Mercury began the better ignition era.
CCW (Kyoritsu Noki) was a well made engine, too.
They did not disassemble a Kohler. I wish they had because they were good solid engines.
They also disassembled JLO Rockwell and BSE (Taiwan) in the Moto-Ski.
You could probably find it by goggling "Inside the New Snowmobile Engines" in Popular Science.
That Mercury 644cc was under stressed when it was introduced in 1972 with only 35 hp. With that power it had a BMEP of 59. The BMEP of the 1970 Snow Cruiser 200's Kohler 309cc with 20 hp was 76.4. In 1974 Mercury brought the power up to 50 hp, which was in line with the 1974 Evinrude Skimmer 646cc at 50 hp.