Maximum RPM Issues on modified 2014 SR Viper LTX SE

[AndyB]

I also am having some issues with my 2014 SR Viper LTX SE getting anywhere near the max RPM's. I had Allen Ulmer machine both the primary and secondary and set up both clutches for the low elevation sport trail riding that I do out here in Maine; using the 8DN belt. Amongst a plethora of other modifications on this sled it has the Ulmer air intake system, re-flashed ECU by EVO Powersports with the "2.5 flash" (9800 rev limit, timing adjustment based on 91 octane minimum), a Bikeman Performance open exhaust (LOUD!) and a different gearing ratio Allen suggested so I could get the sled around 105-110 MPH. Total weight on sled (rider and all gear) when riding is around 265 lbs. I also verified that at WOT the throttle bodies are indeed opening up all the way and they are... I originally thought this might be the culprit.

The original primary clutch setup from Ulmer had the cam arms weight at 6-0-3 (heel to toe). 2 washers to the left side and 4 washers to the right side on the heel--- nothing in the middle--- 3 washers to the left side at the toe. Primary clutch has a black spring. The secondary has the red spring in it with a different helix Allen put in there. I have no squealing and the belt sits "ever so slightly" above the secondary. The deflection is good as well.... only 1- 1mm washer per bolt on the backside of the secondary. I have no wear marks on the primary or secondary from the belt. The clutches run pretty darn cool anytime I put my hand on them to see if they are getting hot after riding for a bit.... the actual sheaves have some heat on them but placing my hand on the front of the primary or secondary there is very little heat.

My dilemma is that at WOT I was only getting 8400 RPM MAX! I spoke to Allen last week and he said to take off ALL the toe weight which I did and that got me up to 8600 RPM MAX. I am WAY LOW from where I should be. I would think with all these mods I should be able to run around 9600 give or take. The sled is topping out at 85 mph even with the gearing change. The sled originally had good low end pull and felt good all the way to WOT. After taking off all the toe weight I feel I lost a tiny bit on the low end pull but seemed to pull nicer in the mid range.... again just my "feelings."

I do not know if the belt is traveling all the way to the top in the primary or all the way to the bottom in the secondary. Not sure how to test this? Can I put the sled on a stand and go to WOT with no load on the track? I would think I can't do that.? Is there another way to verify this? Sharpie marks on the sheaves and see if they get worn maybe?

Trail conditions here in Maine are pretty darn solid... that is the actual trails! GREAT conditions for trying to go as fast as possible in a straight line... not so great for cornering! (there have been a few deaths in the state already from the icey conditions and people dying from "blunt force trauma" hitting trees going around corners at excessive speed)

I left a voicemail with Allen the other day on the results of the toe weight being removed. I am just waiting for a call back now.... he's SUPER BUSY this time of year I know... and he's in "hot demand" by us all trying to get his expert opinions! I am leaving for a weekend riding trip tomorrow so I am hoping to get some input on what other changes I can make to get me closer to the 9600 RPM (105-110 mph) or so.

thanks in advance... Andy B.

 

[TD Max]

Let's start by checking your base weights to see what the number is. There are 50Y and 50YS.

Then the primary spring. It is black, but should have colored dots on it to signify the rate. It should be Orange, Pink, Orange.

 

[AndyB]

ok-- the sled is up at camp so I can't answer these right this second but I will check and get back to you on Friday morning after I arrive. I am leaving tonight. THANK YOU very much! Andy B.

 

[Mitch Desorcy]

What is you secondary spring wrapped at 3-3, 6-1.?? also i don't think you need to be that high in max rpm.

 

[TD Max]

One good combo with the 50Y is to run one tungsten and 2 washers in the heel nothing middle and then tune peak RPM with the tip. 2 washers, 1 washer, or zero. I would think at least 1 washer.

Secondary 6-2 is what I run. Some like less wind, but I find it hits hard like this.

If they are 50YS then 4 washers heel, 6 washers tip but I never really had much time with these yet.

Be sure that you are running fresh gas etc. I know mine odes not pull big RPM, but never as low as yours. Maybe your header is cracked?

 

[AndyB]

Thanks for all the good info. I just got off the phone with Allen. Such a nice guy and a pleasure to work with. He thinks it could possibly be a bad spring in the secondary or maybe a bushing in the secondary getting bound up. He said for me to take it off, take a good look at it for any obvious issues and then if I don't see anything obviously not right to then try putting the stock secondary spring back in it. If the secondary spring is indeed the issue then the stock secondary spring should, at this point in the setup, get much more RPM's and then probably bind up at the inevitable higher MPH. At that time I'll know it's the secondary spring as the issue and he'll send out a new one. Guess, I'll test that out tomorrow. Easy enough.

My primary spring is black with orange-pink-orange on it.

My secondary spring is red and in the 6-1 slots.

The gas in my sled is ALWAYS fresh. I always put in 93 as well. Once in a while when out on the trails and in longer trips I only get 91 as an option at the pump (highest they carry at a lot of gas stations in Maine) and that's when I put in a couple gallons of 97 unleaded, ethanol free (Renegade Fuels-- I am a distributor of theirs) to help insure I get at least a minimum of 91 if the pump gas isn't quite up to spec. I carry 4 gallons of it with me in the Rotopax cans affixed to the rear of the sled.

Still don't know what base weight the cam arms are.... I'll have that info tomorrow afternoon when I get to the sled.

Again, THANK you all for the info! VERY MUCH appreciated. Love learning! Andy B.

 

[TD Max]

I wish we could get 93 here again. When it dropped to 91 my Harley suffered. After a couple years of jacking around I finally got smart and pumped in a couple of gallons of VP 110 at a filling station and the torque came back!

 

[AndyB]

Ok... Got to camp and checked the primary cam arms.... They are 50Y.

I did the initial inspection and the clutches seem to be in good working order. Therefore, I did a bunch of testing making changes to the secondary spring as requested by Allen. I also spoke with him today before my testing because he mentioned yesterday a 6-1 setting and mine was in a 3-3 setting and wanted to verify the change to 6-1.

According to Allen it appears I have a bad red spring in the secondary. Here are the results from my changes in the secondary spring:

Primary still at 6-0-0 (heel to toe) for washers. Never changed this during today's testing.

Secondary red spring at the 3-3 setting was getting me 8600 rpm.

Secondary red spring at the 6-1 setting got me 8800 rpm.

Secondary red spring at the 6-2 setting gave me the same results of 8800 rpm.

Secondary stock black spring with pink line on it at the 6-1 setting got me 9100 rpm. Same with the 6-2 setting.

Conditions are dry, clear, sunny day at 25 degrees F. Trails are hard but had maybe an inch of fresh snow on them.... I packed it all up good with all the runs I made! I made 4 runs at WOT per change. To get to the flat straight away I had to ride about 4 miles from camp each time so I believe I gave the clutches ample time to warm up between changes.

Allen is sending me out a new red spring since mine is apparently defective. He said these results are good and not to change anything after I get the new red spring and put it in the 6-1 setting... Figures I'll get around 9100 rpm with the new red spring and if the temp were to drop to roughly 10 degrees F I could see 9300 rpm.

 

[RJH]

Does it stay at that rpm or drop

 

[AndyB]

It seems to hit that 9100 then drop to 9050 or 9000 and then maybe climb back to 9100. . Never more than 9100 so far. After today's riding (same conditions as yesterday but around 15-20 degrees F) I was around 8900-9000.

I am about to jump into the garage and verify track tension and ski alignment. I don't think they are wrong but I am stumped with what is going on here....

Top speed today was 83mph at 9000 rpm. Way off for this setup....

 

[AndyB]

So last night I checked track tension and ski alignment. Found a couple things....

Ski alignment was right in spec.

When taking the belt off to do track tension (so I can more easily spin the track by hand) I noticed that the belt is not going to the top of the primary. It appears to be approximately 3/8" from the top! I put some white out lines on the primary earlier in the day and the belt wore down the lines except the very top 1/4 to 3/8. Not sure how to get it to ride higher?

Track tension was 1.75" at 25lbs of downforce. I loosened it to 2" This appeared to have helped quite a bit. I was getting 9300 RPM's consistently all day today! Sled tops out at 92 MPH. Conditions are the same as yesterday... Maybe a tiny bit warmer.. 29 - 30.

So, now, how can I get the belt to ride higher in the primary?

 

[cannondale27]

So last night I checked track tension and ski alignment. Found a couple things....

Ski alignment was right in spec.

When taking the belt off to do track tension (so I can more easily spin the track by hand) I noticed that the belt is not going to the top of the primary. It appears to be approximately 3/8" from the top! I put some white out lines on the primary earlier in the day and the belt wore down the lines except the very top 1/4 to 3/8. Not sure how to get it to ride higher?

Track tension was 1.75" at 25lbs of downforce. I loosened it to 2" This appeared to have helped quite a bit. I was getting 9300 RPM's consistently all day today! Sled tops out at 92 MPH. Conditions are the same as yesterday... Maybe a tiny bit warmer.. 29 - 30.

So, now, how can I get the belt to ride higher in the primary?

Go faster. It will get up there.

 

[AndyB]

Cannondale,
Thanks as always for the info.... I WISH I could go faster! That's the issue.... I WANT more speed!!! When Allen set up the clutching and gearing it was to get 105-110 MPH out of the sled with my fat@** and gear (265-270 lbs total). That's what I am hoping to get once things are finally where they need to be.

I maintain WOT for nearly a mile or so....then I run out of lake! None of the trails give me that long of a clear, open, safe run so I try and do the testing, when possible, on the nearby lake.... now that is is frozen! The sled is staying pretty much at 9300-9350 RPM's now pretty consistently. I guess just loosing up the track a bit more really helped! I know 2.25" is the max recommended by the manual and I might loosen it up to that and maybe squeeze a little more speed out of it. 2.25" just seems so loose from a visual standpoint... sags down quite a bit to me.

I can clearly see now, that what appears to be my final issue, is that the belt isn't getting all the way to the top of the primary. It's missing by quite a bit (.25" - .375")! Could this be a situation caused by me now running the stock secondary spring instead of the red one Allen supplied? Would a slightly longer belt, like one from Ultimax (Pro Belt: 138-4432U4) help? From initial comparison to the 8DN belt it seems a little longer and ever so slightly less wide. I do remember Allen mentioning something about the stock secondary spring and the red spring both having the same spring rates... just the red one is made from skinnier metal... at least that's what I took from that comment! That said, the replacement red spring won't change anything, would it? Or would it give slightly more "compression" since it is skinnier... thus allowing the belt to ride lower in the secondary and ultimately higher in the primary? I would think that if I can get the belt to ride to the top of the primary it'll make up the difference I am looking for since it is off quite a bit?

Thanks again for the help thus far. Andy B.

 

[TD Max]

At 9300+ you need to add some tip weight. That or a Gates belt to drop your RPM.

 

[cannondale27]

And you misunderstood. If the power is there to make the belt go to the top then you will be going faster. Who cares if it's not at top? Maybe it's further down in secondary giving you same effective ratio as if it were at top and not down in secondary. Power/speed.