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Zr 800 gearing?

10659 Views 12 Replies 7 Participants Last post by  Auggie
Has any one tried 25/38 in there 800's, My old T-cat had it's hands full this weekend with my buddys 800, told me he's running 25/38, had excellent top, thinking of setting my wife's 800 like that...
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     I'll tell you what, the gearing change to the ZR800 works and there's no two ways about it! My buddy has a bone stock '02 X Country ZR800 and he could barely squeak by me on my '01 MXZx 800 with Dynoport pipe and can as well as a Goodwin clutch kit a few weeks ago. Last week, he obliterated me, both out of the hole and from a 30-40 MPH roll on. His only mod was changing the top gear to a 25 tooth. I guess gearing up doesn't really effect out of the hole other than tending to keep it from not spinning, which is good. Midrange is explosive. He put 4 lengths on me withing seconds after we punched it from 30. He made NO clutching adjustments after the gear swap. The clutching on the '02's is spot-on from the factory. Hit it, and it goes right to 7400 and stays there. No dip, no creep. Later. he raced another buddy's stock '01 T Cat and they ran EXACTLY even all the way up to "speedometer needle over the "M" in "MPH" speeds, run after run after run. This in 1500 or so feet at 1000 Ft. altitude, 20 degrees F., hardpack on the lake with all sleds studded with 192. His only change to the sled was to switch from the stock X Country 1.25" track to a 1".

Hey, I'm a Ski Doo guy and I promise you, THAT THING CRANKS!!!
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Interesting. I know he did have to change to a longer chain, but I'll have to ask him about the driven shaft gear.
I just went over your calculations. I'm new to all this, so I don't understand exactly what they mean. I can see that you add the number of teeth of both sprokets, then take the average, then add 40. I understand the math, but not the rationale. Am I to understand that with this formula (40 being a constant related to the shaft-to-shaft center spacing on this sled?), you need a chain that has at least the equivalent of 1/2 of a link greater length so you can properly tension it?

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