Let me help...I've got a 1992 Mach 1...you have a 617 Rotax, dubbed a "Type 643", which is a faster engine than either the 583 or 670. I was clocked by radar several years ago at 5 degrees and hard-packed snow at 123.3 mph in fully stock form. You have found a rocket when tuned right. I have yet to find a better all around sled (with exception to powder...it sux for that). Have fun!!
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