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Discussion Starter · #1 ·
I have no information or knowledge about gearing, except for what i have learned on here. That said, i have gotten teh general understanding about it, and the performance gains it can give.

I'm asking for those with actual knowledge and info to offer, to help me get a better understanding of the situation.
I'm looking at gearing my SKS 700.

So you drop a gear on the top of the chain case for better low end torque? This is what i would be going for in my sled.
A bigger gear does what? A smaller gear does what? Different for different locations?

2010823113511626_23167.jpg
 

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Its all a ratio...I will try and find you a chart (or if someone else has one to post) that shows the different gears combo that will equal a "ratio number" Closer to 2 is more lowend, better response. Closer to 1 is more your topend, lake crossers looking to do 110 or so.


2010111064158448_19621.jpg

OK so my sled was (i think) a 23/41 ratio that equaled 1.78 and went to a 22/41 = 1.86 so closer to 2, or a 21/39 also equals 1.86. The differnce is the chain pitch. Need to know what the sled is geared at now and where you want to be. I would think being a "mountain sled" it would have a gearing ratio closer to 2 already? Hope this was some help.
 

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Google Polaris Gear Chart

Dropping a tooth on top has the same effect but is not equal to adding a tooth on the bottom.
Adding a tooth on the top has the same effect but is not equal to dropping a tooth on the bottom.

Changing teeth on the top gear has a bigger effect because it is a much smaller gear to begin with.


Say you've got 18/41 right now (39/21 = 1.86)

If you want better top end you want that ratio to go down, making your track RPM closer to engine RPM. (maybe use 39/22=1.77)
If you want better acceleration you want the ratio to go up, lower track RPM. (maybe use 39/19=2.05)
 

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Discussion Starter · #4 ·
Ok, thanks guys, two very helpful posts!
What is reccommended, adding a tooth on the bottom, or taking one from the top, and why? The top, because its smaller, as mentioned? If you change one gear, do you need to change the other?

My SKS would have the stock gearing in it now, don't know what that is but i know theres some people on here that do.
I'm looking for good low end acceleration, don't care much for top end long as she goes over 70.
 

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Stock for your sled is a 23/40 (1.739 ratio)
 

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try to geta gearchart for your sled online , it will tell you every gear every ratio any what pitch chain you will need i found one for my sled posted it here very helpfull. i thought 1 on the top gear was closer to equaling 2 to 3 on the bottom gear ?
 

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Discussion Starter · #8 ·
Whats some advice i can get about how to setup the system on my sled?
 

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You can drop one tooth on top to get a 1.82 ratio.
The gearing chart says dropping two teeth on top (to a 1.9) is not recommended.
A good ratio would be a 22/41 (1.86), but then you need to get two gears. Either the 22/40 or 22/41 would work out pretty good I think.
 

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Discussion Starter · #10 ·
And that is good low end, because its closer to 2?
 

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tdgbigfoot said:
And that is good low end, because its closer to 2?
Yes, higher ratio gives you better low end acceleration.

A good way to think about the gearing is to comparable it to a bicycle.

When you start from a dead stop, it's easiest to start out in low gear (this is gearing down in sled terminology)- that is with the chain on the smallest front "drive" sprocket or the biggest rear "driven" sprocket. This ratio makes it real easy to get going, but if you're going 20 mph, your legs have to be spinning very fast just to maintain speed. (Your legs are analogous to the sled's motor). With a ratio set up like this, your motor is going to over-rev when if you keep giving it throttle at high speeds.

If you have the bicycle chain on the large front sprocket or small rear sprocket (high gear, or gearing the sled up), you know how hard it is to start pedalling from standstill. Same thing with the motor, the acceleration will be pretty bad, but once you get up to higher speeds, your legs (the motor) can easily maintain constant speed and will even increase your top speed with little additional effort.

Should mention that the front "drive" sprocket on a bicycle is equivalent to the top gear on a snowmobile (since it is more or less connected to the power source, where the bottom gear (rear bicycle sprockets) is connected to the device the puts the power to the ground to use as forward motion.

Hope this clears the air for many people.
 

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Discussion Starter · #12 ·
Polaris_Parts_MN said:
tdgbigfoot said:
And that is good low end, because its closer to 2?
Yes, higher ratio gives you better low end acceleration.

A good way to think about the gearing is to comparable it to a bicycle.

When you start from a dead stop, it's easiest to start out in low gear (this is gearing down in sled terminology)- that is with the chain on the smallest front "drive" sprocket or the biggest rear "driven" sprocket. This ratio makes it real easy to get going, but if you're going 20 mph, your legs have to be spinning very fast just to maintain speed. (Your legs are analogous to the sled's motor). With a ratio set up like this, your motor is going to over-rev when if you keep giving it throttle at high speeds.

If you have the bicycle chain on the large front sprocket or small rear sprocket (high gear, or gearing the sled up), you know how hard it is to start pedalling from standstill. Same thing with the motor, the acceleration will be pretty bad, but once you get up to higher speeds, your legs (the motor) can easily maintain constant speed and will even increase your top speed with little additional effort.

Should mention that the front "drive" sprocket on a bicycle is equivalent to the top gear on a snowmobile (since it is more or less connected to the power source, where the bottom gear (rear bicycle sprockets) is connected to the device the puts the power to the ground to use as forward motion.

Hope this clears the air for many people.
That was an awesome explanation! thank you for taking the time to write it!
Appreciate your help!
 

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1tooth change on top gear is about 2x the change that a tooth on the bottom gear.

in theory lower gearing, or taller ratio means quicker acceleration.

for best performance you want to gear as tall as you can until you lose desired acceleration using timing equipment not the seat of your pants.
 

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Discussion Starter · #14 ·
Does everyone agree that a setup 22/41 would be a good setup for my SKS?
 

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tdgbigfoot said:
Does everyone agree that a setup 22/41 would be a good setup for my SKS?
Yes, it will have good acceleration and you will be able to keep the same chain.
 

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Polaris_Parts_MN said:
tdgbigfoot said:
And that is good low end, because its closer to 2?
Yes, higher ratio gives you better low end acceleration.

A good way to think about the gearing is to comparable it to a bicycle.

When you start from a dead stop, it's easiest to start out in low gear (this is gearing down in sled terminology)- that is with the chain on the smallest front "drive" sprocket or the biggest rear "driven" sprocket. This ratio makes it real easy to get going, but if you're going 20 mph, your legs have to be spinning very fast just to maintain speed. (Your legs are analogous to the sled's motor). With a ratio set up like this, your motor is going to over-rev when if you keep giving it throttle at high speeds.

If you have the bicycle chain on the large front sprocket or small rear sprocket (high gear, or gearing the sled up), you know how hard it is to start pedalling from standstill. Same thing with the motor, the acceleration will be pretty bad, but once you get up to higher speeds, your legs (the motor) can easily maintain constant speed and will even increase your top speed with little additional effort.

Should mention that the front "drive" sprocket on a bicycle is equivalent to the top gear on a snowmobile (since it is more or less connected to the power source, where the bottom gear (rear bicycle sprockets) is connected to the device the puts the power to the ground to use as forward motion.

Hope this clears the air for many people.
when you re gear do you have to re clutch ?
 

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Discussion Starter · #17 ·
Winks84 said:
Polaris_Parts_MN said:
tdgbigfoot said:
And that is good low end, because its closer to 2?
Yes, higher ratio gives you better low end acceleration.

A good way to think about the gearing is to comparable it to a bicycle.

When you start from a dead stop, it's easiest to start out in low gear (this is gearing down in sled terminology)- that is with the chain on the smallest front "drive" sprocket or the biggest rear "driven" sprocket. This ratio makes it real easy to get going, but if you're going 20 mph, your legs have to be spinning very fast just to maintain speed. (Your legs are analogous to the sled's motor). With a ratio set up like this, your motor is going to over-rev when if you keep giving it throttle at high speeds.

If you have the bicycle chain on the large front sprocket or small rear sprocket (high gear, or gearing the sled up), you know how hard it is to start pedalling from standstill. Same thing with the motor, the acceleration will be pretty bad, but once you get up to higher speeds, your legs (the motor) can easily maintain constant speed and will even increase your top speed with little additional effort.

Should mention that the front "drive" sprocket on a bicycle is equivalent to the top gear on a snowmobile (since it is more or less connected to the power source, where the bottom gear (rear bicycle sprockets) is connected to the device the puts the power to the ground to use as forward motion.

Hope this clears the air for many people.
when you re gear do you have to re clutch ?
Pretty sure you don't, no
 

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I would like to add speaking from experience if you gear up but don,t have the motor to pull it your clutches may compensate and not shift out fully and you may actually lose top speed.
 
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