tagoes10s
New member
I'm going to start tuning in my Clutch. But being fairly new at working on clutches I want to get an idea of how a well tuned aggressive trail clutch setup acts. Not so much what combinations get you there, but more how does it act when its there. How do you know when you have it tuned in? What do you look for when your tuning in a clutch? My motor should make peak hp at 9,100 rpm. We can use that as a basis.
I would think the first step is tuning is making sure clutches are cleaned, inspected, offset and center to center are checked.
Then dial in RPM with the primary.
Set engagement at the RPM that your track bairly has traction. If you blow the track off, back the engagement RPM down. If it's bogging raise the engagement point.
Next, tune in a 0-top speed run. Engagement is set correctly, so I stab the throttle and RPM's Should flash too XXXX within about XXX feet RPM's should.................... ????????? then top speed at full shiftout RPM should be at xxxxxxx? How should bottom end, middle, and top end be judged? by feel? by RPM? Both? etc which do you tune first?
Then set backshift?
Then make sure clutches are warm not hot to the touch?
Anyone want to share there steps in dialing in a clutch set up?
Dan
I would think the first step is tuning is making sure clutches are cleaned, inspected, offset and center to center are checked.
Then dial in RPM with the primary.
Set engagement at the RPM that your track bairly has traction. If you blow the track off, back the engagement RPM down. If it's bogging raise the engagement point.
Next, tune in a 0-top speed run. Engagement is set correctly, so I stab the throttle and RPM's Should flash too XXXX within about XXX feet RPM's should.................... ????????? then top speed at full shiftout RPM should be at xxxxxxx? How should bottom end, middle, and top end be judged? by feel? by RPM? Both? etc which do you tune first?
Then set backshift?
Then make sure clutches are warm not hot to the touch?
Anyone want to share there steps in dialing in a clutch set up?
Dan
I would say heat is your biggest tool along with your tach. A hot clutch is telling you, " I am very inefficent and wasting power!" If your front clutch is hot, you know you need to work on that front, same goes for the rear but the whole trick in this is to find the best all around set up which gives you decent clutch temps and all the characteristics your looking for such as backshift for on and off the gas, twisty trails require this, long lake racing doesnt. That means tune the clutch's to what kind of riding you do 90 percent of the time and just deal with the other 10%, win or lose because setting the sled up for the 10 percent will result in a very unhappy owner. You cant have the best drag set up and the fastest sled top speed on the lake, cant happen with a snowmobile clutch. To get one thing you must give up something else in another area.
You will want to usually set up your sled to leave from a stop to full throttle holeshot at the peak torq output of the engine, this will be lower then your peak hp number is. You want to load the engine at peak torq rpm and then let it build the rpm up to your peak hp rpm.
1.) start off with your rpm being adjusted correctly, all this is done basicly with the primary clutch.
2.) you tailor or controll the shift with your helix and spring combo it acts to fine tune the upshift created by the primary overcoming the spring with the centrifical force being generated by the flyweights.
You will want to usually set up your sled to leave from a stop to full throttle holeshot at the peak torq output of the engine, this will be lower then your peak hp number is. You want to load the engine at peak torq rpm and then let it build the rpm up to your peak hp rpm.
1.) start off with your rpm being adjusted correctly, all this is done basicly with the primary clutch.
2.) you tailor or controll the shift with your helix and spring combo it acts to fine tune the upshift created by the primary overcoming the spring with the centrifical force being generated by the flyweights.
Lets add this, lets just say you brought your sled here and we take it out to the test field, heres what I would look for when riding it.
1.) Wheres the sled engage the belt at? is it too high or too low for the engine work and or traction available?, I would guess at 42-4500rpm on snow for your paticular sled.
2.) When rapidly accelarating the sled what does the tach do, is it a clean rapid sweep up to the peak torq output of the engine?
Or does it gain rpm then actually lose rpm for a short bit and then begin to climb? doing this is a result of overshifting, meaning the clutchs are getting ahead of the engine, can be caused by too steep of a helix start,too weak of a secondary spring, way too much traction for the engagement speed and thus pulling the motor way down from peak torq.
3.) After getting out about 400ft is the tach climbing up to peak hp and does it stay there? if it does good your getting a decent straight shift profile, if it doesnt then it needs attention, youd start to look at the spring rates and profile of the weight your using.
4.) After its wide open does the tach stay on peak and if you encounter a snow drift or what ever increases drag on the sled does the sled lose rpm? If it stays on target, good, if it falls this is a sign of not backshifting and keeping the engine on peak, can be caused by too steep of a secondary helix finish angle, along with too soft of a secondary spring setting, or too soft of a secondary spring, meaning you need a stiffer rate.
5.) After I made this 750ft or so pass on the sled, stop the sled and its time to open up the clutch cover, is the primary hot? can I hold my hand on the sheave face for more then 3-4 seconds without instinctively pulling away cussing? Can I do the same to the secondary? heat means your slipping the belt, needs either more weight, less shift out tension on primary spring (another sign will be overevving of rpm on peak)
for every problem you encounter there is 3 ways to fix it, one will be better then the other and will do something differnt then the other 2, key is finding the best one that applies to you and your riding style and hangs onto the belt with the least amount of waste!
This process is GENERAL, its meant to give you a idea of what to look for and what maybe to cure the problem, As Turk said continous wide open passes will heat up the clutch's,and belt, especially a 8dn, they like to hold the heat once hot. I tune then let it cool, and retune, this process can last a hour if I guess right, or all day!!
1.) Wheres the sled engage the belt at? is it too high or too low for the engine work and or traction available?, I would guess at 42-4500rpm on snow for your paticular sled.
2.) When rapidly accelarating the sled what does the tach do, is it a clean rapid sweep up to the peak torq output of the engine?
Or does it gain rpm then actually lose rpm for a short bit and then begin to climb? doing this is a result of overshifting, meaning the clutchs are getting ahead of the engine, can be caused by too steep of a helix start,too weak of a secondary spring, way too much traction for the engagement speed and thus pulling the motor way down from peak torq.
3.) After getting out about 400ft is the tach climbing up to peak hp and does it stay there? if it does good your getting a decent straight shift profile, if it doesnt then it needs attention, youd start to look at the spring rates and profile of the weight your using.
4.) After its wide open does the tach stay on peak and if you encounter a snow drift or what ever increases drag on the sled does the sled lose rpm? If it stays on target, good, if it falls this is a sign of not backshifting and keeping the engine on peak, can be caused by too steep of a secondary helix finish angle, along with too soft of a secondary spring setting, or too soft of a secondary spring, meaning you need a stiffer rate.
5.) After I made this 750ft or so pass on the sled, stop the sled and its time to open up the clutch cover, is the primary hot? can I hold my hand on the sheave face for more then 3-4 seconds without instinctively pulling away cussing? Can I do the same to the secondary? heat means your slipping the belt, needs either more weight, less shift out tension on primary spring (another sign will be overevving of rpm on peak)
for every problem you encounter there is 3 ways to fix it, one will be better then the other and will do something differnt then the other 2, key is finding the best one that applies to you and your riding style and hangs onto the belt with the least amount of waste!
This process is GENERAL, its meant to give you a idea of what to look for and what maybe to cure the problem, As Turk said continous wide open passes will heat up the clutch's,and belt, especially a 8dn, they like to hold the heat once hot. I tune then let it cool, and retune, this process can last a hour if I guess right, or all day!!
Last edited:
tagoes10s
New member
Exactly what i'm looking for!!!!!!!!!!!!!!!!
So on the holeshot RPM's should immediately go to peak torque (8,300??) and then gratually climb to peak hp RPM (9,100) or slightly past (9,300)???? and maintain until top speed has been achieved? How far out should the transition go from peak torque to peak hp RPM? 300 feet?
Clutch temps should just be warm to the touch right? 100 degrees F?
I'm trying to tune for a very aggressive trail setup. I think most people in this forum is after that as well. I know if your strickly after top speed, or drag racing or only trail performance then it would be different for each. But I like to run the trails aggressively, but stop at a local field/lake and try to run for bragging rights.
So on the holeshot RPM's should immediately go to peak torque (8,300??) and then gratually climb to peak hp RPM (9,100) or slightly past (9,300)???? and maintain until top speed has been achieved? How far out should the transition go from peak torque to peak hp RPM? 300 feet?
Clutch temps should just be warm to the touch right? 100 degrees F?
I'm trying to tune for a very aggressive trail setup. I think most people in this forum is after that as well. I know if your strickly after top speed, or drag racing or only trail performance then it would be different for each. But I like to run the trails aggressively, but stop at a local field/lake and try to run for bragging rights.
Last edited:
Get a moderator, this needs to be in the tech section. great write up Don... man that should be in a book. Maxdlx
Even after 4-5 back to back runs your clutches will be hot no matter how well your set up is. Just a heads up & a good post by MR Viper.
yamaholic22
Active member
Turk said:
As he said, and the more traction you have the hotter they will be. Do a lot of testing and you will see this no matter how good the setups are.
I will see if I can get this added tonight...thanks
Tom
Tom
tagoes10s
New member
Keep writing Don! Don't stop now!
Turk? others you have to have a few insight tuning tips that will help us out as well...
Turk? others you have to have a few insight tuning tips that will help us out as well...
Ok, I deleted it all..............................LMAO!!!!
I fixed all the mis spelled stuff I could see and incomplete statements.
I hope someone gets some help from it, its not the law, its just my way of doing it.
to answer post 4 questions:
A.) theres no law on the given distance you use but about 300-400ft is good for the tach to start raising in my opinion, the torq has carried you as far as your gonna go, time to get up into the hp to get your mph.
B.) youll have to check out a dyno sheet for cpr pipes to know where your peak torq curve is on a triple viper, I dont know it off the top of my head.
c.) on ebay they sell little digital pyrometers to measure heat when you point them at a object, they are slick and work great on clutch faces, try and shoot for 100-120 temp wise, you can get cooler sometimes, sometimes a bit hotter, but like I said try and get the coolest you can with it doing what your wanting it to do charactor wise. The greatest thing is when your all done youll have other ideas and you can try new things to set ups, I mess with stuff all the time, your never done...LOL
I fixed all the mis spelled stuff I could see and incomplete statements.
I hope someone gets some help from it, its not the law, its just my way of doing it.
to answer post 4 questions:
A.) theres no law on the given distance you use but about 300-400ft is good for the tach to start raising in my opinion, the torq has carried you as far as your gonna go, time to get up into the hp to get your mph.
B.) youll have to check out a dyno sheet for cpr pipes to know where your peak torq curve is on a triple viper, I dont know it off the top of my head.
c.) on ebay they sell little digital pyrometers to measure heat when you point them at a object, they are slick and work great on clutch faces, try and shoot for 100-120 temp wise, you can get cooler sometimes, sometimes a bit hotter, but like I said try and get the coolest you can with it doing what your wanting it to do charactor wise. The greatest thing is when your all done youll have other ideas and you can try new things to set ups, I mess with stuff all the time, your never done...LOL
Last edited:
Olav Aaen's book in condensed form with a MRViper twist.
I like it!!!
I like it!!!
can you bring the entire thing in one post and email it to me, so I dont miss anything 
tagoes10s
New member
Thanks Don, for putting the time in to explain this for us. Very much appreciated.
your more then welcome, anytime!
hope it helps give ya guys a sense of direction from my point of view, like I said, theres MANY ways to do this, my way is not law its just what works for me.
hope it helps give ya guys a sense of direction from my point of view, like I said, theres MANY ways to do this, my way is not law its just what works for me.
RIVERRUNNER
Active member
Wow, Thanks for breaking it down! This really will help me out this winter; I cant wait to test out some of the info!!! Maybe even burn a ditch pickle or two 
Rambunctious
New member
I have one question regarding peak torque vs peak HP at launch.
In theory, with a cvt, you would want a step function to peak HP and stay there.
HP is HP, or energy per time or force x velocity or Torque x rpm. It all reduces to Watts or lbs-ft/sec .
if an engine is at peak torque, you are probably at a reduced power than peak power. the energy transfering through the belt to the secondary is less than at peak power, theretically not transmitting the most energy to the track at that given ( instant) track speed..
The exception may be that the inefficiency of the cvt at the initial lauch is such that with the engine at peak power, the ratio causes significant losses due to a sharp bent belt at the primary.
to really answer this would be a dyno curve montoring HP in and out of the cvt at various speeds.
just trying to understand through physics and engineering.
bottom line, inperical testing obsorbs all the factors and gets the final answer . ( ie. runs down the lane)
Ramb
B.S. Physics
M.S. Mechanical Enginering
In theory, with a cvt, you would want a step function to peak HP and stay there.
HP is HP, or energy per time or force x velocity or Torque x rpm. It all reduces to Watts or lbs-ft/sec .
if an engine is at peak torque, you are probably at a reduced power than peak power. the energy transfering through the belt to the secondary is less than at peak power, theretically not transmitting the most energy to the track at that given ( instant) track speed..
The exception may be that the inefficiency of the cvt at the initial lauch is such that with the engine at peak power, the ratio causes significant losses due to a sharp bent belt at the primary.
to really answer this would be a dyno curve montoring HP in and out of the cvt at various speeds.
just trying to understand through physics and engineering.
bottom line, inperical testing obsorbs all the factors and gets the final answer . ( ie. runs down the lane)
Ramb
B.S. Physics
M.S. Mechanical Enginering
Torque gets ya moving. I have allways 100% of the time with out fail had a lot better results clutching for torque at holeshot & letting rpm,s slowly climb to peak hp rpm,s at finish. Backshift will be & should be brutal but for the best et & acceleration possible this is what works for me.
yamahaha
New member
- Joined
- Nov 24, 2003
- Messages
- 55
Mike, hope that wasn't one of Kokkee's racing secrets!
The azz dyno will lie to you every time. I have done more clutch testing then you can ever possibly imagine running against other sleds all day/weekend/winter long. Yep; sled seems quicker when it is clutched to hit peak rpm,s at holeshot but try it both ways against another sled same day same conditions with the other sled(s) making zero changes. I shudder when I think how many hours I have invested in clutch testing.What feels faster will be a lot slower....trust me on this one!!!!Tell ya what...line up the sled coming out at 8200 vs the one coming out at 8500 rpm. If traction is equal & sleds are in a similar state of tune the one coming out at 8200 rpm whill drive away from the other sled.
Last edited:
The reason the higher rpms seem faster/quicker is because you have better throttle response & that will fool you every time. Running low starting rpm,s won,t work well for trail riding & specially deep snow because it will kill your backshift & throttle response. Remember the key words in clutching are to gain somewhere you gotta give up something somewhere else. You probably want to see a nice slow steady rise of rpm,s up to 8500.