Viper RTX LE clutching

[TD Max]

Please limit discussion to RTX LE only.

With 300 miles on the odometer it is far from broken in yet, but it is so far off pace it's disgusting.

My 2015 RTX LE has not responded well to known, proven clutching setups. I'd like to discuss potential solutions and not debate which clutch kit is better etc.

I started with Ulmer machined clutches and Ulmer clutch kit with 8DN belt. Top speed really hit the wall at 77 mph. I could manage to squeak out 80 barely.

With all of the hype over the 8FP COTC setup I decided that I had to try this to see if it helped. Results mixed, but top speed essentially the same.

Either clutch setup pulls hard until 60-70 mph then flattens out quickly.

Yesterday we ran a bit over 60 miles. Beginning of ride was railroad grade for several miles. I did not have opportunity to hold wide open for long. Then we hit the tight, twisty stuff for the majority of the day. At a midpoint break I popped open the side cover to have a look at the clutches. Clutch temps were mild and teh surfaces looked clean with no striping. Much of my magic marker line was till visible showing that I was far from full shift.

The last leg of the trip was back on the railroad grade and I had longer stretches to wring it out. I was able to manage 80 mph speedo on one stretch then upper 70's. Watching the tach, I see it settle in at 8,000 then build to 8600 range. RPM seemed to become more and more inconsistent on further attempts.

This is with 8FP weights, 3.5g rivet, GWG spring, pink secondary with 6-2 wrap on a poorly degreed BDX helix. By my calculations the 6-2 wrap is equal to a 6-1 on the OE.

Note at the mid ride check the magic marker line was longer and dark where it begins to fade.

 

[TD Max]

I'll kick off the discussion with a couple of observations:

The RTX has a 1.7" lug sno-x track which is stiff and pumps a lot of air. NOS PRO runs 104 mph with 153" 2.25" track which tends to neutralize this theory.

The RTX LE is geared at 21/49 (2.33) versus 24/50 (2.08) on std models. I find it interesting that the Standard and the LE hit the same wall but at different speeds.

To me this indicates that the gearing is impacting in some way. Something like clutching efficiency as the ratio shifts more deeply. Otherwise with teh gearing change, we should see the LE models pull up to max shift more quickly than other models.

 

[weasel33]

Two rtx les. One with Ulmers kit one totally stock. On a long straight away mine ( totally stock ) could only reach 74 mph, on a downhill. Needless to say I'm way unimpressed! Down low the thing has really good grunt but when it hits 70 mph it slowly climbs to 74 and hits a wall, totally unacceptable for a 15000 dollar sled. The 2001 Polaris 600 with almost six thousand miles blew my doors in up top. My max rpm was 8912 and my fuel mileage was between 10 and11 mpg. I know the sled still needs to brake in some because it only has 320 miles on it but hitting a wall at 74 mph is pretty bad even being brand new. Ulmers clutch kit was only a little better up top, it was able to hit 77 mph on the same downhill. Didn't want to turn around and go back up the hill for the fear of not being able to crack seventy! Both sleds got the exact same gas mileage but the Ulmers kit has a lower and much smoother engagement. I'm sure more miles on the sleds will help but I don't think, without something significant being done, will get these sleds even to hit the ninety mph mark. Hopefully talk to Ulmer and the dealer tomorrow and come up with some kind of fix.

 

[TD Max]

My CVT knowledge is limited, but I have a pretty decent understanding of gearing.

Final drive ratio was a subject of discussion years back. This was regarding trucks and dyno HP with varying gear ratios. An engineer contact explained it in very simple terms: Final ratio does not affect HP to the ground. It affects the amount of time the engine spends in a given transmission gear. All things created equal the lower the gearing (higher numerical) the quicker the machine should be shifted and through the gears.

Now enter the CVT and the TQ sensing aspect and the plot thickens. In simple terms one would think that a helix change for a faster shift would be in order, but someone more in the know will have to flesh this part out.

 

[Studroes144]

My CVT knowledge is limited, but I have a pretty decent understanding of gearing.

Final drive ratio was a subject of discussion years back. This was regarding trucks and dyno HP with varying gear ratios. An engineer contact explained it in very simple terms: Final ratio does not affect HP to the ground. It affects the amount of time the engine spends in a given transmission gear. All things created equal the lower the gearing (higher numerical) the quicker the machine should be shifted and through the gears.

Now enter the CVT and the TQ sensing aspect and the plot thickens. In simple terms one would think that a helix change for a faster shift would be in order, but someone more in the know will have to flesh this part out.

Different helix for faster shift is good, but generally you'll need lighter primary weights in order to pull the steeper angles so it's kinda give and take, can't expect to go with a much more aggressive helix and run heavy weight settings and make it work.

 

[shagman]

I'll kick off the discussion with a couple of observations:

The RTX has a 1.7" lug sno-x track which is stiff and pumps a lot of air. NOS PRO runs 104 mph with 153" 2.25" track which tends to neutralize this theory.

The RTX LE is geared at 21/40 (2.33) versus 24/50 (2.08) on std models. I find it interesting that the Standard and the LE hit the same wall but at different speeds.

To me this indicates that the gearing is impacting in some way. Something like clutching efficiency as the ratio shifts more deeply. Otherwise with teh gearing change, we should see the LE models pull up to max shift more quickly than other models.

21/40 is 1.90 not 2.33 just thought i would let you know.

 

[Yam4Strokin]

I think he meant it has 21/49 gearing, not 21/40 gearing.

 

[Kerrdog569]

Ok just ran out and took a picture of mine and this is after a 60 mile ride on Saturday

 

[Curtis Chambers]

My Rtx le is stock can only hit 82mph and only 150 miles so far was goin to try the clutch set up you guys are posting. Something doesn't seem right I'm glad you started this is thread. (1 1/4 " track)

 

[MrSled]

So are you saying the clutching on the cheap does not work? or just not in your sled?

 

[weasel33]

Mr sled, my blue and white rtx le is stock clutch, my brothers rtx le in blue and white has ulmers kit an td max blue and white rtx le has cotc and none of the sleds are responding well to any of them. No top end and ten mpg. Seems that it's just this specific sled that there is no none good clutch set up for.

 

[MrSled]

Mr sled, my blue and white rtx le is stock clutch, my brothers rtx le in blue and white has ulmers kit an td max blue and white rtx le has cotc and none of the sleds are responding well to any of them. No top end and ten mpg. Seems that it's just this specific sled that there is no none good clutch set up for.

I thought those were geared to be a low speed ditch banger... 10mpg... what a pig.

 

[mike_snow45]

Just sharing what I have seen on my 2014 RTX Viper. I understand this isnt a LE but im just sharing because of similar modifications. I have the Ulmer secondary machining, 8DN belt, Ulmer Clutch kit, Excell exhaust and about 650 miles on my sled. I hit 101 pulling around 8700 to 8800 rpm in Munising, Michigan on trail 7 when I was the riding with Master of Faster and a few others on a long straight away. I can pull 90+ pretty much whenever I want but yes that getting over 100 takes good conditions. This is just what I have seen and collected when I am out riding. Maybe the taller track is the issue but even if so i would think you could still pull alittle higher speeds than that. Hope you can get it figured out.

 

[Curtis Chambers]

If anyone has had good luck with clutching could you please post with results and what you have done. I would like to do something soon. The 600's are killing me and laughing and saving $5000. It's not right.My first Yamaha in ten years and not the happiest.

 

[500champ]

seen 94 mph on my white and blue rtx all stock, replaced the 1.7 track for a 1.25 and changed gears to 22/48 and saw a increase to 98 mph with stock clutching and belt