My RTX LE-1.7 clutch testing speed report

[TD Max]

The sled: 2015 SR Viper RTX LE Gearing 21/49 (2.33 ratio) with 9 tooth drivers. Odometer about 450 miles. First oil change done at 300 miles. Mods: MBRP can, DIY air box mod. Windshield is stock low unit


I will put all of my cards on the table in an attempt to present this in as unbiased fashion as it gets. I would also like to make it known that this was done primarily as a top speed test. It would have been really nice to have a nice controlled area and a radar gun with software to log runs to see any changes in the acceleration rate.


The players:

TD Max- that’s me

Ulmer Racing- I purchased my clutch kit and various clutching related mods from Allen at retail price. I owe Allen thanks for a high quality product.

Stingray- Bill developed the COTC recipe and the DIY air box mod that I did. Credit where due

NOS-PRO- Terry provided the clutches off his sleds including COTC setup for testing. I owe Terry a debt of gratitude for going out of his way to help

Cannondale27- Steve provided his expertise, some helpful tools, his version of Ulmer’s weight setup, and some wrenching and test piloting. I owe Steve a debt of gratitude for his service.

Ryan- Steve’s sidekick for the day. I owe Ryan a debt of gratitude for his patience.





Day 1:
Present were TD Max (230# in gear) Cannondale27 (160# in gear?), and Ryan our observer

Saturday Jan 24 2015 Willow Reservoir Temps were in the mid 30’s most of the day. About 33°f at the time of testing. Snow very wet and packy. Snowman making and snowball fight snow. Path was somewhat rough as well.


TD Max sled 80 mph using Ulmer kit as delivered with the exception of secondary being wound at 6-1 vs 6-2.

Cannondale's sled ran 92mph in same conditions


Side by side with Cannondale:

My sled would jump a big lead due to hookup (skis off the ground) of the better track and probably the gearing as well. At around 60mph where my acceleration rate starts to fall off Cannondale will pass me with great ease and just keep on pulling as I would creep up to my 80 mph peak.


Day 2:
Present were TD Max (230# in gear) Cannondale27 (160# in gear?), and Ryan our observer

Sunday Jan 25 2015 Pokegama lake Lac Du Flambeau. Temps in the low teens. Snow was nice and crisp with excellent grip and decent slip. Path was a good bit smoother than the day before. There were a couple of spots that you could feel the resistance drop like a good ice runway, but still decent drag.


Setup 1: 88 mph with me on sled. Cannondale’s version of Ulmers weights. Basically a swap of location of the added pucks from heel to tip. Now that’s a welcome sign.

Setup 2: 90 mph with Cannondale on sled. Terry’s primary with Ulmer secondary

Setup 3: 91 mph with Cannondale on sled. Terry’s primary and secondary

Setup 4: 90 mph with Cannondale on sled. Terry’s primary and secondary with less wrap

Setup 4a: 88 mph with me on sled Same config as setup 4 just more operator weight and height

So at this point it looks like we can conclude that the sled picked up some nice mph right? Well not so fast. I’m smarter than that and I know we need to go back to the setup from day 1 especially with the condition changes.

Setup 5: 88 mph with me on sled with 89 showing just briefly. This was the Ulmer setup from day 1.


Side by Side with Cannondale was the same story. It may have taken a bit longer for him to catch me, but we did not really focus on anything but speed. Also worth noting there was a 2 mph difference based on direction of travel. The wind was very minimal, but it did seem to match wind direction.

Conclusion:

I think Weasel is finding the same thing. Both Ulmer and COTC are excellent setups, but there’s really no clear advantage in regards to top speed. The LE sleds are just plain running a good bit slower on top speed. It's looking like it it boils down to gearing or the track or both. Hoping someone else can test the gearing next. Just a quick change to 24-49 (2.04) should be close enough.

 

[NOS-PRO]

TD, once again....you are very welcome bud and I would do it again in a heartbeat, for you or anyone else trying to figure out their sled

Thanks to Cannondale for picking up the clutches and bringing them to you for you to try Having him here as a moderator, being a good friend to ride with and test with has been priceless

Thanks to Stingray for realizing the Viper needs more tip weight and more grip on the belt.

 

[nherbst454]

Thanks for the well laid out data, I'm going to get a chance to test the latest setup with added weight in hole 2 of the 8FP weights on a lake this weekend, hopefully it will keep it from bouncing off the rev limiter around 85 and shift the primary clutch out further for greater top end.

Setup as it sits now...
Stock secondary spring with wrap at 6-1, may also try 3-3 this weekend
46/40 Dalton Helix
Machined secondary for spring pocket to eliminate binding
Primary G-W-G Spring with 2mm shim
8FP weights, 4.5g in the tip, 3.1g in the middle hole
8DN belt with secondary machined for it as well as OSP belt adjuster
MBRP Trail Can

Hoping for cool temps and some snow for slide life on the lake!

 

[weasel33]

Everyone keeps saying they are hitting the rev limiter. TD have you? The top rpm's I have seen was with cotc at 9032. My brothers sled has only seen around 8850( I can't remember the exact #) but his did hit 79 where mine only hit 77. I would say the gearing is bringing it down but that shouldn't have to much to do with the rpm's, should it??? I thought the clutches controlled the rpm's and the gearing was more about speed or bottom end power. Can someone explain why most are hitting the rev limiter and it seems like these le's don't.

 

[TD Max]

No I have not hit the rev limiter with the exception being a hard spin out on a launch which is quite rare with the deep lug.

 

[stingray719]

The sled: 2015 SR Viper RTX LE Gearing 21/49 (2.33 ratio) with 9 tooth drivers. Odometer about 450 miles. First oil change done at 300 miles. Mods: MBRP can, DIY air box mod. Windshield is stock low unit


I will put all of my cards on the table in an attempt to present this in as unbiased fashion as it gets. I would also like to make it known that this was done primarily as a top speed test. It would have been really nice to have a nice controlled area and a radar gun with software to log runs to see any changes in the acceleration rate.


The players:

TD Max- that’s me

Ulmer Racing- I bought my clutch kit and various clutching related mods from Allen. I owe Allen nothing

Stingray- Bill developed the COTC recipe and the DIY air box mod that I did. Credit where due

NOS-PRO- Terry provided the clutches off his sleds including COTC setup for testing. I owe Terry a debt of gratitude for going out of his way to help

Cannondale27- Steve provided his expertise, some helpful tools, his version of Ulmer’s weight setup, and some wrenching and test piloting. I owe Steve a debt of gratitude for his service.

Ryan- Steve’s sidekick for the day. I owe Ryan a debt of gratitude for his patience.





Day 1:
Present were TD Max (230# in gear) Cannondale27 (160# in gear?), and Ryan our observer

Saturday Jan 24 2015 Willow Reservoir Temps were in the mid 30’s most of the day. About 33°f at the time of testing. Snow very wet and packy. Snowman making and snowball fight snow. Path was somewhat rough as well.


TD Max sled 80 mph using Ulmer kit as delivered with the exception of secondary being wound at 6-1 vs 6-2.

Cannondale's sled ran 92mph in same conditions


Side by side with Cannondale:

My sled would jump a big lead due to hookup (skis off the ground) of the better track and probably the gearing as well. At around 60mph where my acceleration rate starts to fall off Cannondale will pass me with great ease and just keep on pulling as I would creep up to my 80 mph peak.


Day 2:
Present were TD Max (230# in gear) Cannondale27 (160# in gear?), and Ryan our observer

Sunday Jan 25 2015 Pokegama lake Lac Du Flambeau. Temps in the low teens. Snow was nice and crisp with excellent grip and decent slip. Path was a good bit smoother than the day before. There were a couple of spots that you could feel the resistance drop like a good ice runway, but still decent drag.


Setup 1: 88 mph with me on sled. Cannondale’s version of Ulmers weights. Basically a swap of location of the added pucks from heel to tip. Now that’s a welcome sign.

Setup 2: 90 mph with Cannondale on sled. Terry’s primary with Ulmer secondary

Setup 3: 91 mph with Cannondale on sled. Terry’s primary and secondary

Setup 4: 90 mph with Cannondale on sled. Terry’s primary and secondary with less wrap

Setup 4a: 88 mph with me on sled Same config as setup 4 just more operator weight and height

So at this point it looks like we can conclude that the sled picked up some nice mph right? Well not so fast. I’m smarter than that and I know we need to go back to the setup from day 1 especially with the condition changes.

Setup 5: 88 mph with me on sled with 89 showing just briefly. This was the Ulmer setup from day 1.


Side by Side with Cannondale was the same story. It may have taken a bit longer for him to catch me, but we did not really focus on anything but speed. Also worth noting there was a 2 mph difference based on direction of travel. The wind was very minimal, but it did seem to match wind direction.

Conclusion:

I think Weasel is finding the same thing. Both Ulmer and COTC are excellent setups, but there’s really no clear advantage in regards to top speed. The LE sleds are just plain running a good bit slower on top speed. It's looking like it it boils down to gearing or the track or both. Hoping someone else can test the gearing next. Just a quick change to 24-49 (2.04) should be close enough.

Many thanks to Terry for doing the low altitude version of the COTC, wouldn't have happened without him.

Max, I have a chain and 41 tooth sprocket from a 200 mile sled, pay what you think its worth if you want it. Took off a 21/41 XTX.

Note: I geared my 2014 XTX converted to an MTX (21/41 - 7 tooth drivers and 3.0 pitch) about the same gear ratio as TDMax has and it pulls amazing to about 70 to 75 and falls off fast....if this info helps at all

 

[TD Max]

I would sure like to think a 162" X3 pulls a lot more windage and load than a 129 1.7.

What I don't get is why we aren't coming up to the rev limiter. With the shorter final it should get there more easily than the taller geared machines. The taller geared machines run faster mph AND build RPM at the end of the run

 

[cannondale27]

TD you arent hitting the rev limiter because all the setups we tried were made not to hit the rev limiter. Just take some weight out of any of those setups and you will bang the rev limiter.

I checked the springs. According to parts your springs are same as mine.

 

[sneakattak88]

TD Max, im going thru the same pains with a LTX LE , just today i ordered new gear,, im going with a set of 24/41 and a new chain.. this is my last hope to slove this gremlin

 

[cannondale27]

Awesome report!

 

[500champ]

I guess all the fast ones got sent to AK, we seen 90-94 mph box stock no mods on 4 different white and blue RTX LE's with the 21/49 gearing and 1.7" tracks running across the lakes

 

[weasel33]

TD, maybe Yamaha gave us the duds because we complained too much about our shocks!

 

[500champ]

TD, maybe Yamaha gave us the duds because we complained too much about our shocks!

U werent the only ones that complained, I dont understand why such a huge speed difference? Same sleds 10-15mph difference

 

[weasel33]

500, did you verify that you have the same gears as us? What is the last four didgets of your vin?

 

[500champ]

500, did you verify that you have the same gears as us? What is the last four didgets of your vin?

Yes I did verify 21/49, same sled as you guys, I verified when I done track swap, 94mph was to slow, speed verified with gps and speedo (within 1/2 mph of each other)