850 Gear Down ?

[2XM3]

yup back in the day on my NA 903 with a chaincase I had the biggest possible gear I could cram in there on the bottom and a stupid small one on the top, that thing was a beast for sure, id have run the chain on the shaft if I could have lmao


What gears are you running in there now ? Think I had 18/46 in mine had a 17 top as well lol

 

[damx]

Put the pro gears in today , rode 44 miles. Kind of hard to tell if I like it over stock gearing yet, sled was climbing awesome, just felt like it was not pulling as hard. Never did any clutching from the stock gears. Rpm was 8100-8200 I'm going to go to the other helix angle that is 2 degree steeper.

 

[Nitroused383]

To update on this we ran one sled without the gear down and one with. It's quite a substantial difference in a drag race. The sled with the gear down would pull away hard all the way through the range. My dad finally geared his down and now both sleds are dead even. 5500-6000' elevation both sleds are turning 8150 rpm with 72g stock polaris weights 163 2.6 about 43 mph track speed in heavy snow that was rained on. Running 91 non ethanol fuel in non ethanol mode about 16 hours on both sleds now.

I realize the gear down skews the speedometer reading so does anyone know what the corrected mph would be?

 

[Mentzel]

Draw 3 vertical lines with sharpie on the belt contact area of primary clutch. Ride for a day and check wear marks. If the belt doesn’t ride to the top or within a 1/4” you need to “gear down” (increase ratio). It’s amazing the difference it makes when you use the entire clutch. Polaris had been using some weird calculation that sets gearing to only use 50% of the clutches. If your sled has some miles it takes a bit to break in the top of the clutch. But once it wears in the sled shifts so much better. If the 850 is geared for 85 mph track speed at 8250 [emoji1304].

 

[tdblakes]

What’s the torque spec for the QD bolts?

 

[Teth-Air]

45 lbs/ft but upgrade to a 10.9 hardness bolt

 

[Teth-Air]

I did a little searching but not a lot of info yet, so I thought I would start a thread on gearing down or just general gearing changes on the the 850.

First, anyone try the Pro gears (gear down) on the new 850? I know this was / is popular with the 800, in fact I did this upgrade on my 2017 and had good luck with it.

Second, anyone upgrade to the Kurt's gear down or the TKI set up? If you are running the TKI, what gears did you go with and what was the outcome ?

Anyways, just looking for some thoughts and feedback.

TKI with 25:58 but I had the chaincase if you have quickdrive you get a 63 tooth bottom gear with the TKI kit. The final gearing equivalent to 8 tooth drivers works great at 2.42:1 for shorter tracks or 2.52:1 for longer tracks. Spins much freer than the chain and even the quickdrive as Polaris runs them banjo tight.

 

[tdblakes]

45 lbs/ft but upgrade to a 10.9 hardness bolt

Thanks. Got some ARP 663-1006 replacements on the way

 

[damx]

So I have 250 miles on my 850 with the pro gears and im now getting belt slip on the top of primary, it leaves rubber marks. I also went from 10-72 to 10-74 And I'm pulling 8200-8300 @4000'. It seams the clutch does not have good belt grip when geared down, I'm about 3/4" from the top of the primary according to the marker line. Anyone else have this problem or know how to for it.

 

[revrider07]

Need to gear up

 

[damx]

I would like to leave it geared down if possible.

 

[kanedog]

Need to gear up

That is incorrect information.

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[revrider07]

That is incorrect information.

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Just went through this on Friday at low elevation on mine put more weight on primary belt was slipping on top end so I geared up two teeth on top this is with a three inch belt stopped slipping. I normally don't ride this sled at home but I needed to last week. I would bet your sled feels like it hits a wall at the top but feels like there is more there. The helix and spring combo could help also but you already have the stock gearing. One thing to remember this is not an 800.

 

[Teth-Air]

So I have 250 miles on my 850 with the pro gears and im now getting belt slip on the top of primary, it leaves rubber marks. I also went from 10-72 to 10-74 And I'm pulling 8200-8300 @4000'. It seams the clutch does not have good belt grip when geared down, I'm about 3/4" from the top of the primary according to the marker line. Anyone else have this problem or know how to for it.

If your primary is slipping near the top it is likely slipping at the bottom too as there is less belt contact when the belt is down low. Are you sure you are not getting water (snow) on the clutches when you see the black marks? Gearing up puts more torque load on the belt so it would slip more with all else things considered equal. I always go with a stiffer secondary spring on the AXYS to hold back the shift a bit and put more belt grip in the secondary but never see your issue with the primary unless the weights are way to light. Yours are not too light.

 

[damx]

It could be snow/ water dripping on the clutches but I have frog skinz on the hood vents, and sealed up all the gaps around the bulk head to the body panels. And I never seen water dripping when I took a look.

 

[revrider07]

Dmax I know what you are trying to achieve but IMO if you spend a bunch of money of a new clutch set up you will still be geared wrong for maximum performance. Whenever I get less than a 1/8 inch of marker left on my primary I risk breaking the belt going wide open that's why I gear up when I want maximum performance at sea level. The stock spring and helix were designed for elevation riding.

 

[kanedog]

Just went through this on Friday at low elevation on mine put more weight on primary belt was slipping on top end so I geared up two teeth on top this is with a three inch belt stopped slipping. I normally don't ride this sled at home but I needed to last week. I would bet your sled feels like it hits a wall at the top but feels like there is more there. The helix and spring combo could help also but you already have the stock gearing. One thing to remember this is not an 800.

Nope. Mine keeps pulling and pulling. The engine "grunts" as as the engine is loaded through the track, not the clutches. Light weights, light springs, gearing is so high(3.48) and annhiliates any NA sled that its not even believable . Turbo killer. This is in the mountains. Flatland I have no experience.
I do know of the wall that you are talking about though. It does take a lot of test and tuning to fix that.
If you are looking to fix belt slippage by gearing higher(numerically lower), you went the wrong way.

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[d8grandpa]

Kane, are you running gear or belt drive?

 

[revrider07]

Kane I agree at elevation but on flatland is different and the load is also different I've spent lots of time and money. I have aeons clutch book and know it inside and out. Somthing to think about when drag racing at sea level a geared up sled will crush one that's geared down to far. Have you ever broke a belt going wide open with both clutches shifted out. There is a fine line. Trs has this down pat for elevation and understands how to make both clutches work together to achieve top track speed in different conditions.

 

[damx]

I am mountain riding just low elevation 2000-4000' and we have wet heavy snow most of the time. I try and find what works good in Alaska, because that is around the same elevation. I have tryed a few different clutch kits and nothing is working good yet.