Maximum RPM Issues on modified 2014 SR Viper LTX SE

[AndyB]

Cannondale and TD Max,
Sorry for the lag in response here on this topic. Been VERY busy with work. I really appreciate both your inputs.... you both definitely know way more than I on this topic for sure!

Cannondale is right, I am not completely understanding this... I would think that in order to get maximum top speed from the sled one would need (from a clutching standpoint alone) to get "full shift out?" I think full shift out would be defined as the belt riding to the very top of the primary and the very bottom of the secondary? Coincidentally, I am having this EXACT same issue on another Viper (RTX- turbo'd). On both machines the belts are not getting to the top of the primary (missing by 1/2" or so) and they are also not getting to the bottom of the secondary (1/2" or so from the bottom). I do notice I am getting spring binding in the secondary on both machines. The red spring (in both sleds) compresses itself to the point it can't compress anymore and is evident by the red paint being "ground" off wherever the sides of the metal spring come in contact with each other throughout the spring.

Both machines clutches were setup and machined by Allen. Both sleds had gear changes (Allen came up with the gear ratio and supplied the gearing) to achieve their respective top end speeds. Both Viper's clutches seem to be in perfect working order. The secondaries, when taken apart and removing the red spring can open wide enough to allow the belt to the bottom. Both primaries have smooth movement and nothing binding up in anything what so ever. Nothing is worn out.

So, are there other adjustments that would allow the belt to ride lower in the secondary and thus ride higher in the primary? Is the red spring not the right one? The stock spring does the same thing as the red one. I even tried an Arctic Cat yellow spring! Even that behaved the same way. All 3 springs get me the exact same results.

Although I am not happy with this thought because it admits "defeat" and is a compromise, I am thinking at this point just to use an Ultimax Pro belt (138-4432U4 Yamaha 89L-17641-01-17641-00) which I believe is slightly longer than the 8DN belt. I am thinking this will ride down the exact same distance in the secondary as the 8DN but be able to go a little higher in the primary thus giving me a little better top end, even though I'm not getting the full potential from the machines?

TD- why would I want to add tip weight on the primary in order to drive down the RPM's slightly? Wouldn't I want as many RPM's as I can squeeze out of the machines without hitting the rev limiter? With the EVO re-flash in both sleds I can go as high as 9799 before I hit the rev limiter. Wouldn't more RPM's equal more top end I could get assuming my clutching (and everything else on the sled's) were setup properly to capitalize on it?

Thanks again for all the advice & guidance. Andy B.

 

[TD Max]

Nobody is running 9300 that I am aware of. It seems that just a tick over 9,000 seems to be the sweet spot. The extended rev limiter allows for some overshoot on a launch or instantaneous loss of traction.

On the red spring binding I don't think that is possible with that one. The OE pink definitely does though.

 

[murdered141]

Not trying to hijack your thread but I had a very similar issue with similar mods, 15 viper ltx dx, ulmers k&n intake, ulmer header, sandale can, big venom clutch kit and Evo stage 4 flash, I couldn't break 84 mph and 8600 rpm, although the motor felt like it was making great power, with all my mods the power level is comparable to a low boost turbo as I was told by some, but the lack of clutching knowledge and no time to test or ride for that matter, I bought an mpi turbo, not installed yet, can't help but wonder if lower gearing and a different secondary spring was my answer.

 

[Mills]

I am very interested in what you end up finding and doing with the non-turbo sled. I just picked up a brand new '14 Viper RTX holdover and plan to do the Ulmer Stage#2 trail performance kit, machine clutches for 8DN belt and do the EVO flash. If you are getting coil bind in the secondary is there a spring available with the same or similar spring rate but less coils per inch? That may solve this issue as there will be less coil mass in that space it shifts within which might allow it to fully shift without binding.

 

[scuba_nytro]

This is a long shot, as it sounds as if your not getting full shift, but my buddy had his 16 Viper RTX LE reflashed this fall at the dealer, I think Yamaha's attempt to fix the starter kick back issues. When early season riding he kept complaining how slow his sled was. It turned out the speedo was off because of the flash, it was reading like 10 MPH lower than he was actually going verified by a few different sleds in the group. He called the dealer who had him bring the sled in, dealer loaded a revised tune in and the speedo was back on the money. Have you verified your speed with a GPS?

 

[murdered141]

I never verified with GPS when I had the Evo flash, I sold my intake, clutch kit, and traded Evo flashed ecu with some cash on top for a stock ECU that I need for turbo install, Ecu supposedly came from a just purchased used 14 ltx dx, but I verified this weekend in Munising that my speedo is indeed off by 10 mph,72 speedo,82 phone GPS, so it must have the early flash from this fall, will take it to dealer to reflash, can't have a slow turbo sled. Wish I had verified earlier with Evo flash, that 84 might have been 94 which isn't bad for the mash potatoe snow conditions we've been having most of this year, the Evo flashed ecu came off a 14 xtx so It couldn't have had the Yamaha flash with incorrect speedo reading.

 

[murdered141]

My understanding is that it doesn't matter which gear ratio or driver size you have, because the speedo takes a reading off the magnets on the jack shaft.

 

[cannondale27]

Cannondale and TD Max,
Sorry for the lag in response here on this topic. Been VERY busy with work. I really appreciate both your inputs.... you both definitely know way more than I on this topic for sure!

Cannondale is right, I am not completely understanding this... I would think that in order to get maximum top speed from the sled one would need (from a clutching standpoint alone) to get "full shift out?" I think full shift out would be defined as the belt riding to the very top of the primary and the very bottom of the secondary? Coincidentally, I am having this EXACT same issue on another Viper (RTX- turbo'd). On both machines the belts are not getting to the top of the primary (missing by 1/2" or so) and they are also not getting to the bottom of the secondary (1/2" or so from the bottom). I do notice I am getting spring binding in the secondary on both machines. The red spring (in both sleds) compresses itself to the point it can't compress anymore and is evident by the red paint being "ground" off wherever the sides of the metal spring come in contact with each other throughout the spring.

Both machines clutches were setup and machined by Allen. Both sleds had gear changes (Allen came up with the gear ratio and supplied the gearing) to achieve their respective top end speeds. Both Viper's clutches seem to be in perfect working order. The secondaries, when taken apart and removing the red spring can open wide enough to allow the belt to the bottom. Both primaries have smooth movement and nothing binding up in anything what so ever. Nothing is worn out.

So, are there other adjustments that would allow the belt to ride lower in the secondary and thus ride higher in the primary? Is the red spring not the right one? The stock spring does the same thing as the red one. I even tried an Arctic Cat yellow spring! Even that behaved the same way. All 3 springs get me the exact same results.

Although I am not happy with this thought because it admits "defeat" and is a compromise, I am thinking at this point just to use an Ultimax Pro belt (138-4432U4 Yamaha 89L-17641-01-17641-00) which I believe is slightly longer than the 8DN belt. I am thinking this will ride down the exact same distance in the secondary as the 8DN but be able to go a little higher in the primary thus giving me a little better top end, even though I'm not getting the full potential from the machines?

TD- why would I want to add tip weight on the primary in order to drive down the RPM's slightly? Wouldn't I want as many RPM's as I can squeeze out of the machines without hitting the rev limiter? With the EVO re-flash in both sleds I can go as high as 9799 before I hit the rev limiter. Wouldn't more RPM's equal more top end I could get assuming my clutching (and everything else on the sled's) were setup properly to capitalize on it?

Thanks again for all the advice & guidance. Andy B.

Ok I am just talking Top Speed here. Look at your clutches. Feel them after a run. Hot as heck. Black from belt? If not keep adding wieght and you WILL gain speed and shift. It will be between 8800 and 9200 any more rpm will not give you even 1 mph. The more wieght you add the further your primary will shift. IF conditions let it.

If you see black clutches and heat. Take clutches apart and clean,scuff them. Use a rag with Acetone on it for initial clean. When done cleaning take the rags and that red spring and throw it in garbage. Put stock pink secondary spring back in. Assemble use a new belt if on hand and try again. Look at your Tach using recall and use GPS for Max speed recall. This way you will be accurate,documented and safe since you will not need to look at anything till run is over. Find a safe 1/2mi to do this. Good luck.

 

[My_nanc]

My sled is doing the dame thing. Im shure my secondary is the issue. I am shure i have lots of power amd its not shifting to the top of the primary because of the secoondsry. Tomorrow im goin to take my springs out an move my clutches and see about how my primary and secondary shift woth the 8dn belt. Maybe my secondary spring is binding as well amd its an aftermarket one from big venum. My fastest runs so far are 90mph. Although i also think my spedo is out 10mph after a ride with a friend this weekend. I am slow from the 70mph to the 85ish it usually pulls. But hard all way up to 70mph.

 

[cannondale27]

My sled is doing the dame thing. Im shure my secondary is the issue. I am shure i have lots of power amd its not shifting to the top of the primary because of the secoondsry. Tomorrow im goin to take my springs out an move my clutches and see about how my primary and secondary shift woth the 8dn belt. Maybe my secondary spring is binding as well amd its an aftermarket one from big venum. My fastest runs so far are 90mph. Although i also think my spedo is out 10mph after a ride with a friend this weekend. I am slow from the 70mph to the 85ish it usually pulls. But hard all way up to 70mph.

If your speedo is off you are right in ball park speed wise. It takes a lot of power and tuning and just right conditions to hit over 100mph. Anyone who says different is full of it. As far as the belt riding all the way up that's also bull. CVT clutches are LESS efficient at max shift. That's a fact. My runs at 105mph+ are with belt at less than 1/4 from top in primary. Oh and this will make you feel really depressed. This past weekend on a real fast stretch buddies 7000 gpsed at 103mph! NO mods. Stock everything. It's conditions Bud.

 

[AndyB]

Thanks again. I'll add some tip weight then. 50Y weights with a 4-2 setup at heal, 0-0 for mid and I'll start with 0-1 for tip weight (currently 0-0). Hoping this gets better shift and will absolutely drop the RPM slightly. I'll keep you posted on the progress.

 

[AndyB]

Oh, and I'll start using my GPS for speed assessment... Comparing it to the speedo. I'll keep you all posted.....