Khoas Kurts belt drive testing

[madmax]

I'm always trying new parts on my sleds, some are worth the money some are not. I've been debating for a few months on whether to lower the gearing on my Khaos or not. I have a set of Pro gears that lowers it a little, but IMO they don't go low enough and when I've put the pro gears on other axys sleds I have noticed very little difference. Got 50 miles on my 100% stock Khaos over Thanksgiving weekend. Went up yesterday and rode again. Snow was way deeper than I thought it was going to be. We got 4-5 feet over thanksgiving weekend and another 12" at least last weekend. Best snow I've seen in Utah first week of December in a very long time. I like to add parts one at a time to see what changes they make. When id ask my friends who had Kurts gear down kits if they were a benefit, they all said the gear down and clutching made a big difference. Im like, well was it the clutching or gear down that made the difference? Since my sled was still 100% stock I wanted to see what just the gear down would do riding at close to 10,000. First good play hill I tune on was so steep and deep I could not get out the top. Running max 7900 rpm and 36-40 mph track speed on multiple attempts. Not bad for a stock sled at 10,000 feet. Went back to the truck (only 10 minutes away) and installed the Kurts gear down kit only (no clutch changes). The instructions say to "break in" the belt for 100 miles. Hmmm, not going to happen today. I did get 10 trail miles on it before I couldn't stand it anymore and went for the same hill as before. Once off trail I noticed a significant difference in pop in the front end when I hit the gas that made the sled a lot more fun and playful to ride, especially poping across a creek bed. What I wasn't expecting was the huge difference on the same hill. Got out the top first try, rpms up to 8100 and to my amazement 44-45 mph track speed. I was expecting the rpm to increase some and with that maybe a little increase in track speed, but would not have believed a consistent 5mph track speed increase. I did get the TRS alignment bar last week and aligned my clutches before this trip, they were way off from the factory. After a couple pulls at this hill, pulled the side panel and primary was warm, but could hold my hand on it. The secondary was hotter, but not a lot. Now if I had some clutching to put in I really could have got it ripping, but I was very happy with the $650 gear kit performance. Went home, pulled the skid, track and drivers for the 162 camsno epic 2.8 install.

 

[madmax]

Couple pics.

 

[Sheetmetalfab]

Umm the speedometer reads from the jackshaft.

You should see an increase in shown “trackspeed” just in the percentage you geared it down.......

 

[Wheel House Motorsports]

Umm the speedometer reads from the jackshaft.

You should see an increase in shown “trackspeed” just in the percentage you geared it down.......

Haha yup, always gets me too, easy mistake to made.


Also, FYI, @madmax The Kurts kit for the 850 and the pro pulleys create the same ratio, so you achieved the same results as the pro pulleys, only gains over it are slightly larger radius and softer belt so it does roll a tiny bit more freely. Also clutch sled for 83-8400 RPM and you will really feel it wake up, this motor likes to be spun and has a really tall power curve on top, so clutching for the high end keeps you from getting pulled down out of the power. Now try TRS clutching, your going to be a VERY happy camper, this combo FLAT WORKS, have 4 of them between myself and friends and it pretty much quells everyones desire to run HP mods anymore.


Regardless of the details, the gear down helps 100% just in how the sled snaps up to speed and also keeping you more in the middle of clutch shift vs constantly around. Very worthwhile mod I would recommend to anyone with a belt drive Axys.

 

[Griff]

Kurt offers a kit with a lower ratio, 29/69. I put it on my 800 stocker last year. Seemed like a better gear down option for my riding than only going as far as the Pro's ratio or the same offered in Kurt's 32/67 kit. So far so good.

 

[madmax]

The Kurt’s is axys pulleys are 2.37 and the pro Pulleys are just barely over 2.09.

 

[Lobster Carl]

Kurt offers a kit with a lower ratio, 29/69. I put it on my 800 stocker last year. Seemed like a better gear down option for my riding than only going as far as the Pro's ratio or the same offered in Kurt's 32/67 kit. So far so good.

I have called kurts on 2 different occasions. They told me they do not offer a 29/69. How were you able to get that ratio?

 

[Wheel House Motorsports]

The Kurt’s is axys pulleys are 2.37 and the pro Pulleys are just barely over 2.09.

Gotta read the fine print, its a bit tricky. They quote "final drive ratio of 2.37" so factoring in other drivetrain ratios. This had me confused for a while too.

The included pulleys are 32 / 67 = 2.093 ratio on the pulleys. so virtually identical to pro pulley configuration.
Pro RMK pulleys 21/44 = 2.095

 

[Griff]

I have called kurts on 2 different occasions. They told me they do not offer a 29/69. How were you able to get that ratio?

I called and talked to Kurt about the type of riding I do and where I ride. We discussed both gear sets and I chose the 29/69 gears. Those gears are listed with his 8 inch driver set up on his website currently.

 

[madmax]

This has been the most depressing post of my life. First I find out I probably only picked up jack shaft speed and probably not as much track speed as I thought and now you tell me I wasted $650 on a set of gears that might be the same ratio as the pro gears I have sitting on the shelf?!?! Im not sure if I want to go home and count the teeth on my Kurt’s sprockets or just live on the hope that they might be the 29/69 set. Ignorance is bliss.

 

[bobback]

This has been the most depressing post of my life. First I find out I probably only picked up jack shaft speed and probably not as much track speed as I thought and now you tell me I wasted $650 on a set of gears that might be the same ratio as the pro gears I have sitting on the shelf?!?! Im not sure if I want to go home and count the teeth on my Kurt’s sprockets or just live on the hope that they might be the 29/69 set. Ignorance is bliss.

But you said you could tell a difference on that same hill! And you were on that same hill on the same day, not a day later when the snow was set up more.

To help others considering the gear down kit and for your own piece of mind, go count those teeth.

 

[BeartoothBaron]

Well, in the picture on their website, I count 67 teeth on the lower sprocket from Kurt's kit, so looks like Wheel House is right. It seems like more than one source is using the actual gear ratio combined with a multiplier for going from 8 to 7t drivers. https://www.snowest.com/forum/threads/axys-gearing.437881/ Maybe the good news here is if it's only a jump from 1.96 to 2.09, then your actual track speed has gone up. If it were 2.37 vs 1.96, then taking your lowest number (36 MPH) and multiplying it times the difference (a 21% jump), the speedo would read 43.7 MPH at 36 MPH actual track speed. On the other hand, if I average your before and after speeds and figure a 2.09 vs 1.96 actual difference in ratio, the increase in indicated speed should only be around 3 MPH, so you'd have gained 3-4 in actual track speed. Still, they could make things much simpler by just listing the actual tooth numbers; anything else is just marketing speak.

 

[mountainhorse]

Great post...thank you for putting in the effort to keep us in the loop with your install and testing.

 

[madmax]

I did count the teeth on my Kurt’s sprockets and they are the 2.09 ratio. There was some Improvement in the same day same hill, so that was good. In comparing the Kurt’s and Polaris gears size by side, the Kurt’s gears are a little bigger in diameter and width. I Would like to try a TKI kit now with a lower gear ratio like 2.3 or 2.4 and just see how a lower ratio compares. I’ll post the pics of the comparison of the pro vs Kurt’s gears do you can see the size difference.