Where to start with poor performance

[AftonJay]

So I recently purchased a 2015 Viper STX-DX after my last sled crapped out. Having previously owned a Nytro which I loved the motor but at 6'6" just wasn't comfortable on long days i thought the Viper would be a great sled. After having ridden it a couple of times now I have been rather underwhelmed at the performance. Granted my previous sled was a AC F1000 with some minor clutch mods and Y-pipe so I knew this would be less exciting but this thing is just slow. It has some mods that I thought would make it perform at or above the level of the Nytro but that is just not the case.

The mod list:
Straightline header from Ulmer, primary STM Super tips weights and spring tuned by Ulmer, a different secondary helix and spring I believe also from Ulmer with the sheave turning for the Yamaha 8DN belt, airbox mod with with an additional filter coming out of the front and an EvoPowersports exhaust and intake 91 octane tune.

I have checked and cleaned the clutches, found no issues, the track spins freely I replaced the plugs.

The Supertips weight set is 4-0 at heel, O middle and 4-2 at tip on 50YS weights. I will say I am no expert in clutching so I watched the STM video on set up and he indicates that tip weight is not really desirable unless going for top speed so i don't know if that was the last owners goal at the sacrifice of any low end snap but that is what it feels like.

If anyone has some ideas on what to check for or maybe a better set up on the supertips i would be open to any suggestions.

 

[Srxspec]

Don't let the STM video fool you. That video is for a different style of STM weight (different profile). Your weights are set appropriately. You came off of a sled with 170+ hp on your F1000 and now you're riding a sled that's 145 hp. A Sidewinder would've been a much better sled for matching performance of the F1000 but having the riding of the Pro Cross chassis.

 

[AftonJay]

Thanks for the reply, believe me I am taking into consideration what I was riding. But this thing isn't even in the same ballpark as my Nytro and honestly after going from this to my daughters 2000 zr600 I think if we lined those two up the 600 would probably win.

Worst of all with the tune I am stuck putting 4+ dollar a gallon gas in it for zero performance.

 

[sxr70001]

Yeah lots of discussion about this when the Viper first came out. Lots of dissapointed people. Bottom line is that the Arctic chassis eats up at lot more horsepower than the yamaha Nytro chassis did and cat electronics made it even worse. @cannondale27 probably wrung the most out of his Viper as anyone. I had some luck with extra wheels, fully clipped track, sucking the straps down a hole and running a hindle slip on, but even then it just made it barely get over 100 mph reliably, stock it was hard to hit 90. Sidewinder like what was said is the ticket or turbo the VIper.

 

[AftonJay]

Thanks, that is disappointing. I really don't care about top end but the acceleration is what is so disappointing on this thing, I had read a lot of older posts and saw the comments comparing to the Nytro but figured with the mods it would at least be equal. But apparently this thing is just a dog that may be looking for a new owner or becoming the wifes sled.

 

[AftonJay]

For Srxspec, I am assuming by your profile info you are associated with Ulmer, forgive me if this is out of line. But I will ask anyways, I am slightly heavier than the original owner that did the mods (250 vs 235) and as mentioned more interested in take off and corner to corner. Would you still suggest the same set up with the weights?

Also i noticed when i had the clutch apart for cleaning that the primary spring is shorter than the original that was in a box, is this normal or could it be worn?

attached is the original set up sheet.

 

[Srxspec]

So clutch settings vary on sled to sled, snow settings, etc. If your operating RPM is around 9000-9100 then the clutch is set right. I will say that the part number written on that sheet for the secondary spring (Red) is not the correct spring. If you have that Yamaha red spring installed, the sled would be very lazy.

 

[AftonJay]

Thank you so much for your reply. Would that rpm be like full throttle top out? Or on hard acceleration?

The spring in it is black with orange, pink, orange dots on it. And like I mentioned when I set on bench next to stock it's about a 1/2 shorter which i found wierd.

 

[Srxspec]

Yes, the primary spring is shorter than stock. The spring I spoke about above is the secondary spring. Rpm should flash to 8900+ and maintain that rpm as soon as you go wide open.

 

[AftonJay]

Oh thanks that one is red. It's got an aftermarket helix as well. And the secondary has been machined for 8DN. Still wrong spring? Should I put stock back in?

 

[AftonJay]

Or better yet sell me the correct one (assuming you are affiliated with Ulmer based on profile)

 

[RobX-1]

FYI, he (Allen) is the Ulmer in Ulmer Racing. Have had great success running his clutch setups in my 08 Nytro and 08 Apex. That 08 with over 22k miles is still running strong as the day I slapped his kit on it and yes, that's pretty much all I had to do.

 

[AftonJay]

I figured he was affiliated didnt realize he was the guy thats awesome hes on here helping people out. that's why I felt something was off. Had his clutch stuff on my RX warrior and that thing ripped