Viper power loss found

[stingray719]

Its lost in the clutch, the primary actually. After the 8DN debacle (changing from 8jp to 8dn stopped wild rpm hunting) I went to work studying why this sled was so different from the Nytro clutches. I noticed our Viper came with a 2 stroke profile in the weight. That being a bump in the heel to raise take off revs (as 2 stroke have high horsepower not torque) and then a level ramp for about a third of the profile then a steeper ramp to raise rpm. And yes, why? This is a torque motor not a 2 stroke. I put the flat profile Nytro weights in (Matt from MPI suggested this, and this is what I did to our other boosted Yamahas so it wasn't anything new) and cut to desired rpm and that helped but it still seemed like something was missing. I mean this sled is a lot lighter than a Nytro and should be faster. So I came up with a bizarre test that worked.

All tests with flat profile 8FS weights cut down to 50 grams for above 10k altitude running. Weather about 25 degrees 3 inches snow on top of crust at 10k altitude. Race against 2008 Nytro with Can and a few add ons and a 2012 Nytro with 190hp Turbo


1. Stock clutches - Primary spring 35 open, 101 Shift -----------------------------------------------------Viper slightly slower than Nytro, Turbo blows it away

2. Stiffest primary spring made for this clutch (that I could find) Primary 45 open, 135 shift------------Even up with Nytro, turbo blows it away

3. Green-White-Green (aka Primary 45 open, 135 shift)with 2mm spacer -------------------------------------Viper blows away Nytro, and runs about one length slower than Turbo Nytro from stop to 50mph. Viper doesn't taper off at around 50mph and keeps pulling.

My results yours may vary.

 

[peterg]

thanks Stingray
I test rode a xtx Viper on the weekend and was wondering why it fell on its face at 50 mph, I knew that a stock Nytro could Kick it's *** I was wondering about primary weights. I'm placing my order (snow check) for a new Yamaha blue and whit mtx 153 turbo Viper
in the nest few weeks!!

 

[stingray719]

thanks Stingray
I test rode a xtx Viper on the weekend and was wondering why it fell on its face at 50 mph, I knew that a stock Nytro could Kick it's *** I was wondering about primary weights. I'm placing my order (snow check) for a new Yamaha blue and whit mtx 153 turbo Viper
in the nest few weeks!!

Stock Viper set up correctly in the clutch and a Nytro has no chance. Stock Viper out of the crate does not have enough side force on the belt and slips the belt and won't go full shift out. Mine altered left me with stiff forearms reminded me of my old supercharged Nytro.

My suggestion for that Turbo if they still have not figured it out by then is 8FS weights (flat profile)with rivets set to mid 70's grams and green-whit-green with 2mm spacer. Or spend $400.00 for a clutch kit....JUST KIDDDING!

 

[stingray719]

Its lost in the clutch, the primary actually. After the 8DN debacle (changing from 8jp to 8dn stopped wild rpm hunting) I went to work studying why this sled was so different from the Nytro clutches. I noticed our Viper came with a 2 stroke profile in the weight. That being a bump in the heel to raise take off revs (as 2 stroke have high horsepower not torque) and then a level ramp for about a third of the profile then a steeper ramp to raise rpm. And yes, why? This is a torque motor not a 2 stroke. I put the flat profile Nytro weights in (Matt from MPI suggested this, and this is what I did to our other boosted Yamahas so it wasn't anything new) and cut to desired rpm and that helped but it still seemed like something was missing. I mean this sled is a lot lighter than a Nytro and should be faster. So I came up with a bizarre test that worked.

All tests with flat profile 8FS weights cut down to 50 grams for above 10k altitude running. Weather about 25 degrees 3 inches snow on top of crust at 10k altitude. Race against 2008 Nytro with Can and a few add ons and a 2012 Nytro with 190hp Turbo


1. Stock clutches - Primary spring 35 open, 101 Shift -----------------------------------------------------Viper slightly slower than Nytro, Turbo blows it away

2. Stiffest primary spring made for this clutch (that I could find) Primary 45 open, 135 shift------------Even up with Nytro, turbo blows it away

3. Green-White-Green (aka Primary 45 open, 135 shift)with 2mm spacer -------------------------------------Viper blows away Nytro, and runs about one length slower than Turbo Nytro from stop to 50mph. Viper doesn't taper off at around 50mph and keeps pulling.

My results yours may vary.

A friend in the Midwest tested and the green-white-green primary spring with 2mm spacer and the 8FP weights is the low altitude version of this. His Viper now pulls his Nytro by 4 lengths. Lets get these Viper clutches set up and put this "low power" thing to bed.

 

[OuraySledder]

And here I have been reading how the Yammi clutching was going to be soooooo much better than what Cat offered.... ooooops

 

[stingray719]

And here I have been reading how the Yammi clutching was going to be soooooo much better than what Cat offered.... ooooops

Can't argue with that, they made a mistake on the clutches. If thats the only mistake though I am happy.

 

[TBird]

And here I have been reading how the Yammi clutching was going to be soooooo much better than what Cat offered.... ooooops

Let's see, one is grenading belts, one is not tuned to it's full potential, what's worse?
You don't seem to know the diffrence, AC is grenading belts, Yamaha is not tuned to it's full potential, there you go!

 

[stingray719]

Friend of mine in the midwest did this change to his Viper and it went from his very well running Nytro beating it to what you see in the video....required viewing for our Poo bretheren....lol

https://www.youtube.com/watch?v=JeiNuxIomcE


And yes its for real I had the same results.

 

[stingray719]

More people have tried this and great results, has worked for everybody so far.