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Discussion Starter · #1 ·
From sifting through the forum topics over the last month, I learned that most people recommend running 20/ 39 for the best overall performance. SO I wanted to see what was in mine, It's a 96 xcr 600 with the 680 ultra spx motor in it. I figured it would be a 21/ 39 or somthing like that but here its a 21/ 35.. Never heard of that combination. Anyone run it or know anything about it, just wondering. I'll be sticking the 20/39 set up on it anyway..
 

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if your after speed stay with the 21/35, you are right atgleast according to the info i have gotten that 20/39 is a 2.05:1 or 19/39 and is a 1.95:1, they say 2:1 is about where you want to be, i am going to be doinin a 19/39 or maybe even a 19/40 or 41, i do alot of ditch bangin, i may only top out at 70, but ill be there before you can blink
 

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Discussion Starter · #4 ·
I like the right here right now better myself, so I think I'm still gonna try the 20/39. or 19/39, but do you think I should go from 11 on the chain to a 13? To be on the safe side.
 

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snowmobilexcr said:
From sifting through the forum topics over the last month, I learned that most people recommend running 20/ 39 for the best overall performance. SO I wanted to see what was in mine, It's a 96 xcr 600 with the 680 ultra spx motor in it. I figured it would be a 21/ 39 or somthing like that but here its a 21/ 35.. Never heard of that combination. Anyone run it or know anything about it, just wondering. I'll be sticking the 20/39 set up on it anyway..
Read through this. It should help.
http://www.hardcoresledder.com/forums/438-xcr/420834-ultra-spx-clutching.html
 

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Discussion Starter · #6 ·
Yeah, all good info, however I know nothing about cluthing, I'ts something I will be learning about because it sounds like it has alot to do with just about everything. What is the helix? I have the blue spring in mine, should I change that to the almond? I cont tell whats on the secondary, what do you gotta do to figure that out?.
 

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snowmobilexcr said:
Yeah, all good info, however I know nothing about cluthing, I'ts something I will be learning about because it sounds like it has alot to do with just about everything. What is the helix? I have the blue spring in mine, should I change that to the almond? I cont tell whats on the secondary, what do you gotta do to figure that out?.
Someone posted a video on how to do poo secondarys, ill see if i can find it. The helix is in your secondary. On my 700twin i am running the almond round with 62's, pulls pretty hard.

http://www.snowmobilefanatics.com/forum/topic/101091-rebuilding-clutch#1029891

dtmmil posted the video in this topic
 

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20-39 is xlt/xcr gearing.

21-35 is way to tall for that sled, i ran 22-40 with the 600 case reed for a season and it absolutely rocked. with a light rider on the sled it smoked 800's like nothing. there were other things done to it but 20-39 gearing is to low, 20-37 would be a great starting point.
 
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