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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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Catroy,

     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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Well, you know Roton I think he isn't telling you the whole truth nothing but the truth
. The stock gearing on a "02" ZR800 is 24/39. With this gear setup you would use a 72 pitch chain. Lets do the math.

24 + 39 = 63
63 div. by 2 = 31.5
31.5 + 40 = 71.5 pitch chain. This will work.

25 + 39 = 64
64 div. by 2 = 32
32 + 40 = 72 pitch chain. This will not work unless the chain is quite worn. If you are able to get a 25/39 to work you had better be ready for a broken chain. When the chain breaks you have no brakes. Now maybe there is a 73 pitch chain out there that I don't know about??


   -Auggie-
 

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Auggie is right. I did the math myself and found the same. You can change the gearing but you'll need a chain and gears.  However D&D sells a 74 pitch chain 13wide which is as wide as the stock chain that you may be able to use. In their catalog it is 47$. So if you used a 26 tooth gear it would come out to a 72.5pitch chain needed and you should gain      7-8mph on top end I don't know how much it would hurt the sled off the line though. If you know how to do the math for the gearing you can play around with different ratios to get more top speed.

I did some playing with the numbers you gave a 25/38 will work and a gain of 6-7mph on top end with a 72 pitch chain.
 

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I would say that if you are under 200lbs go to the 25/38 gearing.  I never ran mine with the 24/39 gears, but it pulls very, very hard with these gears.  You will not loose low end, but will gain mid range and top end.
 

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I would say that if you are under 200lbs go to the 25/38 gearing.  I never ran mine with the 24/39 gears, but it pulls very, very hard with these gears.  You will not loose low end, but will gain mid range and top end.
 

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Whoa, sorry about the double post.  Another thing I forgot to mention...I have a speedwerx single pipe on mine, which allows me to turn 7600-7700 RPM.  I have to recommend this pipe for anyone who wants improvement over stock.
 

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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?

Thanks
 

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I don't think cat will put a chain on there that will JUST fit, so he might have just fit that 25 tooth upper gear on there without a chain swap     (i use my stock length T-cat chain for all my gearing swaps, except the 23/39. too high)
 

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Well, Roton you are right. Here is the whole formula.

(CD x 2) div. by .375 + (TG + BG) div. by 2 = chain pitch

CD = Center dist. between the jackshaft and the driveshaft.  
       (Arctic's is 7.5")
TG = Top gear
BG = Bottom gear

Hope this helps.

PS: 1000-IMP a 23/39 will work with a 72 pitch chain. We used this combo in ashphalt drag racing. There is quite a bend in the chain but we ran 10.53/122.2 mph in a 1/4 mile, so it did not seem to be a problem. There is one problem though and that is the chain tensioner bolt might not be long enough. We used a longer bolt but it bent right away. If you go to a longer bolt go to a grade #8.

   -Auggie-
 

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If one of you guys could give me some advice I would appreciate it. My buddie and I both have  02 zr 800 EFI's and his always works good. all he did was gear 23/40 and left everything else stock. I have a Black Magic and D&D clutch kits and have tested both against him. I left my gearing stock and I find that I get the hole shot  and hold it to about 80mph and then he pulls on me. This is pi$$ing me off cause I was told that these kits were suposed to rock all the way thru the power band. What can I do here ?

   Just for the record the BM kit seems to be better than  D&D .
 

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Well, if that were my sled I would install a 38T bottom gear (you can use your stock chain) and reinstall the stock clutching. Make a couple more runs at him and see if things inprove. If they do then install the Black Magic kit (it seems to be the better of the two) and do it all over again. You should drill him, but if you don't you better do a compression test. It should be even and between 130 to 135#. If your comp. is OK then strap your buddie to lie detector mach.


   -Auggie-
 
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