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The bigger question is why? Did you want to gear down a tooth? On a std chain case you just remove the gear and install a smaller one and a new chain, in most cases.
 

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here is a chart it is is not for your exact machine but the numbers still apply
the higher the ratio , the lower the gearing
the lower the ratio the higher the gearing
you will notice that most times it is not just a sprocket change but a chain
change will be required as well depending on what your final result is .
 

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So what do you want if you are looking for low end torque and faster acceleration?
A higher ratio will give you better low-end and faster acceleration..with less top speed......And a lower ratio will have less on the bottom..but faster top speed.

A couple tooth size change will make a noticeable difference.
 

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Atleast on paper! I have found that on some sleds (Yami's) Droping a tooth on the top gear, actually gives More top end speed! And on most stock sleds adding a tooth will slow it down!
 

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Its just as in a mtorcycle sprockets; the smaller the "drive" sprocket the more top end, but you can also add a smaller rear "driven" sprocket to add more top end. More torq is adding larger sprockets. Almost any factory ratio for any machine bike or sled is a 3:1 ratio; this means that every time your drive gear from the endine turns once, the driven gear on the tire or track travels three times the distance. The closer you make the gears in size, the less ratio; this means everytime the engine turns the drive gear it will move the driven gear less distance. Hope this helps, but you can add more top end by either dropping a size on the driven, or dropping a size on the drie gear. If you want more power, add a larger gear to either end, but not both at the same time.
 

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Its just as in a mtorcycle sprockets; the smaller the "drive" sprocket the more top end, but you can also add a smaller rear "driven" sprocket to add more top end. More torq is adding larger sprockets. Almost any factory ratio for any machine bike or sled is a 3:1 ratio; this means that every time your drive gear from the endine turns once, the driven gear on the tire or track travels three times the distance. The closer you make the gears in size, the less ratio; this means everytime the engine turns the drive gear it will move the driven gear less distance. Hope this helps, but you can add more top end by either dropping a size on the driven, or dropping a size on the drie gear. If you want more power, add a larger gear to either end, but not both at the same time.
I think you meant to say "The smaller the drive , the more bottom end"

The closer the gears, the closer to 1:1 you get, which means the drive gear will turn the driven gear at an equal rate.

So what you are saying is gearing ratio's in sleds are completely backwards from automotive differentials or transfer cases in 4x4's? Doesn't make any sense how a lower gearing (higher number), which is accomplished by dropping teeth could give more top speed and less pull on the bottom.

Dropping teeth on the drive sprocket will always give you lower gearing(higher number), which in turn will increase torque/acceleration and decrease top speed.

For most people who just want to tweak for either a little better bottom or top, usually only need up to 2 tooth size difference either way to accomplish their goal.

Larger drive gear=less power and more speed
Smaller drive gear=more power and less speed

Larger driven gear=more power and less speed
Smaller driven gear=less power and more speed
 

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Im smelling what you are stepping in and you are right, but I am also speaking from experience as a certified motorcycle/ATV/snowmobile mechanic. I had two different driven sprockets for my KX 250; a 45 tooth and a 51 tooth. With the 45 I could hit 85 MPH tops, and with my 51 I could only do about 78, but It gave me so much bottom end that it was practically a uni-cycle. In my EXT 580 I dropped the top drive gear from a 21 tooth to an 18 which gave me a ton of low end and far less top. This is where I found some confusion and tried to make sense; "Atleast on paper! I have found that on some sleds (Yami's) Droping a tooth on the top gear, actually gives More top end speed! And on most stock sleds adding a tooth will slow it down!" Kccats. But, gears are gears; its not rocket science. They should work the same no matter what the vehicle theyre in.

So, please excuse me if I confused anyone or got your panties in a bunch, Im only throwing up what my schools and experience have fed me; take it or leave it. Personally there is no need to change a snowmobiles gearing, the clutching is what should be adjusted for performance purposes.
 

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Its just as in a mtorcycle sprockets; the smaller the "drive" sprocket the more top end, but you can also add a smaller rear "driven" sprocket to add more top end. More torq is adding larger sprockets. Almost any factory ratio for any machine bike or sled is a 3:1 ratio; this means that every time your drive gear from the endine turns once, the driven gear on the tire or track travels three times the distance. .

think you have the backwards... its a 3:1 REDUCTION. for every 3 revolutions of your engine (drive gear), the driven gear turns once. Otherwise if your engine was spinning 8000 rpm, your drive train would be cooking along at 24,000 rpm! (aka it would have launched itself into orbit)


the actual size of the sprockets makes zero difference, its just the difference between them. You can get a 3:1 reduction with any number of combinations of sprockets, they will all perform 100% identically.

and yep, some sleds go faster with a higher gear reduction ratio. its not a mystery, its because the engine didn't have enough power to pull the gears with the first combination, or at least the clutching didn't let the engine do it. Its basically the same as some sports cars with 6 speed transmissions. 6th gear on paper is the fastest, but in reality 5th actually turns out to have a faster top speed because the engine can wind out to the max rpms.


(just for the fun of it, I did the calculation if your drivetrain DID turn 24,000 rpm. With 8 inch drivers, you would be going roughly 570 mph!) 24000*8*3.14*60/12/5280=570
 

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Brain Fart.

think you have the backwards... its a 3:1 REDUCTION. for every 3 revolutions of your engine (drive gear), the driven gear turns once. Otherwise if your engine was spinning 8000 rpm, your drive train would be cooking along at 24,000 rpm! (aka it would have launched itself into orbit)


the actual size of the sprockets makes zero difference, its just the difference between them. You can get a 3:1 reduction with any number of combinations of sprockets, they will all perform 100% identically.

and yep, some sleds go faster with a higher gear reduction ratio. its not a mystery, its because the engine didn't have enough power to pull the gears with the first combination, or at least the clutching didn't let the engine do it. Its basically the same as some sports cars with 6 speed transmissions. 6th gear on paper is the fastest, but in reality 5th actually turns out to have a faster top speed because the engine can wind out to the max rpms.


Yep, you are right. I have it backwards. Brain fart. So, the engine will turn the drive gear three times to turn thr driven gear one time; 3:1 reduction. Well, you cant win em all, but if we read through all of this mess we can understand how gearing works. Thanks for the feedback and for correcting my mistakes. Im not afraid to admit that Im not perfect, but sometimes I know my shiz. :cheeky4:
 

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I would suggest changing your clutching over the gearing. It is much easier, and more cost effective. Changing the gears may cause problems with reverse.
 

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What is your engagement rpm at now? You could drop a gram on the weights or put a spring with a higher initial rate and same final rate as you have now.

Although, you do get more pull throughout the powerband with a lower gear, whereas weights/springs just give the effect by raising(in this case) the takeoff rpm which is a little harder on the sled.
 

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i have a 2004 mxz 800 HO renagade 136 " track, im looking to gear down a bit just for a little more hole shot...what would be a not to drastic change for a noticeable differeance?
 

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Just an Q. What if you went from a 121 to a 136. Would you want to drop a tooth or two on the top gear? or should you keep it the same?
 
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