Example Issue - Need more peak mph.

Answers to questions in brackets [answer]
Q) What are your rpms supposed to be on the tach to achieve "actual" rpms. [8200 tach for 8000 actual]

Q) What was wrong with the rpms?....[Nothing or maybe slightly high. Hard to tell]
Consider]...Know that Low or high rpms are wrong. The question to be asked from all this info; Is the operating rpms correct throughout the whole shift range from bottom end to top end mph?

Q) Was the sled sluggish?...[No]
Consider]...could be an overrev issue. If the rpms are low then the TRA lever would be pushing too hard.

Q) Where was it sluggish?.....[The sled wasn't]
Consider]...could be an overrev issue. If the sled was sluggish at a certain mph then at that mph the TRA lever would be pushing too hard.

Q) Where were the rpms wrong?....[They weren’t]
Consider]...could be an overrev issue. Saying correct rpms then the TRA lever is not pushing too hard. Can the TRA lever push harder?

Q) Was the performance good in the bottom end but lacked in the top end?...[Yes]
Consider]...mph good then rpms are good or near-good. Is there the capacity for the TRA lever to push harder?

Q) Did the rpms fall off on the top end?.....[No]
Consider]...There could be capacity for the TRA lever to push harder.

Q) Did the rpms climb from the start to full shift?...[No, basically stayed the same]
Consider]...There could be capacity for the TRA lever to push harder.

Q) Did the rpms be excessive during the whole run?....[No, just fine]
Consider]...There could be capacity for the TRA lever to push harder.

Q)Did the rpms hunt going higher and lower?.....[No]
Consider]...There could be capacity for the TRA lever to push harder.

Q)Was the engine slow to rev?.....[No]
Consider]...There could be capacity for the TRA lever to push harder. If the engine was slow to accelerate; As the engine rpm increase, the force of the TRA lever is being stalled and letting the engine progress with increasing rpms.

Q)When you let off the gas then press the gas again, did the engine hang up on a low rpm?.....[No]
Consider]...There could be capacity for the TRA lever to push harder. If the engine hung up on a low rpm, then at that point along the shift curve the TRA lever was pushing too hard.

Q) What is the personality of the back shift like when you flip the fuel lever; Is the engine quick to rev?....[Yes, very quick]
Consider]...There could be capacity for the TRA lever to push harder.

Q) What mph did you get when topped out?.....[100 MPH on the speedo & feel the sled can go faster]
Consider]...There could be capacity for the TRA lever to push harder.

Q) What kind of temperature did the clutches produce? Primary temp? Secondary temp?....[Primary hot. Secondary cool, but only checked after I thought the belt was overheating]
Consider]...There could be capacity for the TRA lever arm to push harder. Overrev causes primary to get hot then heat transmits through the belt and eventually the secondary will match the temperature of the primary.

This next question tells so much of the clutch system and makes a double check on all previous answers. Once you get to this question, it goes back and acts as sort of a "tattle tale" on any of the previous questions that were not answered "truthfully or correctly".

Q)Did you check your secondary temperature and primary temperature on the sheave faces?.....[Yes]
Comment]...Regarding this question, you are checking for a temperature differential across the clutches.
*Secondary hotter than primary? - not enough belt clamp in secondary.
*A cooler secondary means that the sheaves are clamping the belt hard and more efficiently.

Q)What was the temperature differential between the primary and secondary clutch?....[Primary definitely hotter]



Troubleshooting:
Effect - Primary hotter than secondary | Cause - TRA lever not pushing hard enough. Need more flyweight? or Need less final spring force?
Effect - Primary hotter than secondary | Cause - Could be too much flyweight in primary. Could be too small of final spring force. | Symptoms - The engine rpms come in low and eventually climb to peak and correct rpms - there is excessive belt slip in the primary, the belt climbs too slow in the primary.

Effect - Primary hotter than secondary | Cause - Could be too much flyweight in primary | Symptoms - The engine rpms are fine until near top end mph then rpms start to fall, the rpms start to drift lower and mph flattens out. You quickly stop the sled/engine and feel clutches, the primary is hotter.

There are so many symptoms/clues that I think the TRA lever has the capacity to push harder. You know what the helix and secondary spring details are.
You can look at the clutch and say "Lack of belt clamp."
Now look at the primary as the cause of excessive heat.

How do belts blow? Excessive heat! What is heat caused from? - Clutch slip and rpm drifting. We read the cause/effect/symptoms.

Look at an example system...
*Primary spring 230/360
Q)..How can we get the TRA lever to push harder if we cannot or do not want to change the flyweight?
A)...Change & lower the primary spring final force.<<[Clutching Principle]
Example spring 230/350. At full shift the primary spring has 10 lbs less force pushing back against the TRA lever.

- Fun question - If the primary spring has 10 lbs less force at full shift, how much less force does the spring produce at 5/8's of full shift? Was dropping 10 lbs in the final enough to make a substantial change to notice at 1/2 shift or more? Could a 230/320 primary spring be a remedy?

Another example system...
*Primary spring 230/360
*24g
Q)..How can we get the TRA lever to push harder if we cannot change the primary spring forces?
A)...Change the primary flyweight mass.
Example flyweight mass 24g. You feel your sled can go higher mph. After testing the clutch temperatures you think you can lower the temps by reducing engine rpms. You want to make the TRA lever push harder by adding more flyweight<<[Clutching Principle]. You change to 24.5g or 25g or more.

- Fun question -Going for a test run to top end mph, then upon return to your launch area; What would make you conclude "I've added too much flyweight mass?

Another example system...
*Primary spring 230/360
*24g
*Clicker 5
Q)...How can we get the TRA lever to push harder if we cannot change the spring force or the flyweight mass?
A)...Adjust the primary clutch clicker to a lower number position. Knowing: Higher clicker number = higher rpms = quicker engine response<<[Clutching Principle].
Lowering the clicker number allows the center of gravity of the TRA lever to be farther away from the clutch shaft, thus the harder the TRA lever will push.

- Fun question - Going for a test run to top end mph, then upon return to your launch area; What data detail[s] would make you conclude "I have too low of clicker number for this application?

-------------------
Review
Lack of mph:
*Too low of rpms - TRA lever pushing too hard.
*Rpms drifting, diminishing lower - TRA lever too hard.
*Too high of rpms - TRA arm not pushing hard enough.
*Rpms drifting, slowly increasing - TRA lever not pushing hard enough.
*High primary clutch temperature - TRA Lever not pushing hard enough.

What influences the force personality of the TRA lever?
*Flyweight mass
*Spring force
*TRA clicker position.

Increasing Secondary Efficiency Using Spring Forces

I get this question quite a bit regarding doing economical improvements to the clutch system with a stock sled. Here is an example of gaining efficiency with paying attention to the heat your clutch system can produce from belt slip, how to lower the clutch temperatures and increase performance. There is a point where a tuner can go too far in a certain "tuning window" with spring forces, and then another problem can be created. Excessive rpms, but remember, flyweight determines rpms. So this leaves you option to do what? he he
Never look at it as problems...rather look as an opportunity to capture something and learn in the process. Take notes, they'll be your guide for the pursuit of a "best system".

----- Original Message -----
From: In Quisitivetuner
Date: Today
Subject: Via the MxZx-REVZone website

I have a 2003 HO REV. Just wondering if there is anything that can be done to increase performance by just working with the stock clutch. Are there any way(s) to add just a part or parts "that" will help from the holeshot through mid-range? Not really worried about top end.
Thank you,

I. Quisitivetuner

----------------------------

Joe writes:
Hello: Here is an academic discussion on secondary springs and the capacity they can hold to offer better efficiency in a clutch system.
If you run your sled, you should take note of how your secondary runs for heat.
You go for a run in a predetermined course. At the finish you grab the brake quickly and stop the sled, Pop hood feel temps of clutches.

Heat = belt slip. How can you recover hp and reduce heat to put it to the ground?
Secondary spring? Helix?

To quickly learn what a spring can do for you to reduce heat...
For lack of better springs we can talk of your stock secondary spring = Black 160/300
Options -------
Green Doo = 180/300
Dalton red = 200/300
Purple Doo = 225/300

Since you mention you do not care about top end; all these springs have finish force of 300 lbs. The top end ideally should reveal same performance in mph.
Look at spring forces in bottom end of shift 180/200/225 and neglect the finish forces. What would going to any of these springs help? Each one will offer increased belt clamp force than the former. The sheaves will push harder against the belt in the lower & midrange shift ratios than previous spring. The temperatures revealed will be lower on the same test run with each increase of spring.

There will be an upside to this, increased acceleration if the rpms stay the same to top end and which they should because of the 300 finish force with all springs.
The choices made should pep up your bottom end.

To review the exercise, what tasks did you perform? Think this way; nobody knows your sled better than you.
Now, what questions did you ask to the sled?
*Are the clutches hot? - You stopped at the end of the run and measured the temperature of each clutch.
*Are there correct rpms? - You periodically looked at the tach from start to finish.
*Was the sled sluggish? - You felt acceleration in the seat of the pants "Butt Dyno"
*Where was it sluggish? - You looked at the speedo at particular moments from start to finish.
*What was wrong with the rpms? - You periodically looked at the tach from start to finish. You listened to the engine during the run.
*Where were the rpms wrong? - You looked at the speedo at particular moments from start to finish.[Did the rpms climb or fall?]

I believe the tuner must listen & feel the information from the sled...Instead of people saying "you should try this or you should try that, they should have been asking the questions to you. What does your sled do?" .....gettit?!!

What are your questions? Write them down. Here are some notes;
Too much secondary spring will reveal excessive rpms. At one point or another on during the upshift the primary will not be able to push the secondary open; The spring in the secondary offers resistance clamping the belt so hard that more force is required to open the secondary.

Not enough spring force will cause engine to overrev, the belt will slip at high revolutions across the clutch faces - Especially seen on large bore or large cc triple engines where tuners keep trying to tune with low force springs and large helix angles. The state of tune is going past the governor point of the squeeze force on the belt...the belt slips excessively.

The upside to "Too much spring force" is cool secondary clutch temperature.
...However; On a long run with overrev the overrev condition would produce higher Primary temperatures - Heat indicates Belt slip in primary; indicates area on shift ratio where an overrev takes place.
Heat here is generated when the force from the primary is not pushing hard enough clamping the belt while trying to pull the belt around the sheave. There are more revolutions of the clutch face rubbing a point on the belt as the belt rotates through the arc of the primary. Rpms are high, friction is low, and heat will generate quickly because upshift acceleration is slower.
I think an analogy could be; Would you rather grab a rope and slide down it quickly burning your hands, or increase your grip and slide down slower to keep the temperature down?

If you run long enough in an overrev condition the heat from the primary sheave via conduction will transmit into the belt, which will transmit into the secondary and reveal high temperatures on both clutches.
Leaving the secondary spring alone; how would you cure an overrev problem? Change flyweight? Change helix angle?

The Zoomies = Pipe Surge

The Zoomies is one Tough problem to figure out for tuners regardless of their experiences in clutching and especially tough when a novice tuner has encountered this. After seeing this pipe surge event and figuring it out, you can hear symptoms from other sleds and quickly figure out the problem.

A tuner builds a clutch setup on an engine that happens to have 125 lbs compression. With 17 grams installed on the primary lever, the sled performs very well, good acceleration and backshift response.
The tuner's buddy has the same sled however that engine has 155 lbs. They install the same parts in this 155 lbs sled and there are problems.

***NOTE - The tuner does not know the compression of Buddy's sled is 155 lbs.***

Buddy runs his sled along at 3/4 throttle and maintains 8000-8100 rpm. When he cracks the fuel trigger to the bar, the engine rpm drops to 7500 rpm. Let off the fuel and the engine wakes back up to 8000-8100 rpms. Crack the fuel trigger to the bar, the engine rpm drops to 7500 rpm; Let off the trigger slowly to about 3/4 throttle and the engine wakes back up to 8000-8100 rpms.
What...the...hell...is...going on?!!! After many questions, the tuner eventually gets around to asking Buddy what is the engine compression? Buddy says "155", Tuner replies 155???...Wow!
The tuner having experience with high compression engines run on race fuel, knowing what an engine sounds like if it is not loaded enough, asks..."Did the engine make a sound like "RAH RAH RAH". Did you notice the tach needle bounced up as you held the gas to the bar, the sled surges while trying to accelerate?

Buddy replies "You are explaining perfectly". Buddy being kind of a newbie to the sport has never experienced this condition of Pipe Surge. So I have to say the way it run, he must have thought..."What kind of junk setup did my tuner friend give me?" HAHAHAHAHA

The tuner states this condition was called "Pipe surge" otherwise known as "The Zoomies", "Rah Rah's" or "Wack off's".
Further explanation revealed that the testing was done with engines that had compression of 125 to 132 lbs and that they all took flyweight in the range of 16 to 18 total grams of pin weight.
The Zoomies are caused from the exhaust pipe not heating up quick enough to produce power at proper rpms.
Few ways to get rid of "The Zoomies".
1] Lower the engine compression.
2] Add flyweight to load the engine more.
3] Retard the timing to heat the exh. pipe quicker.
4] Larger start angle on the helix at the start of the shift.
Easiest is to opt for #2 [Add flyweight to load engine more, making the primary push harder]

Tuner's conversation to Buddy:
Add flyweight to 19 grams on the levers and check rpms from there. If you need to add more flyweight to get 8000, then do so. If 19 grams is too much, then less flyweight. Do a MPH check. Try to go wide open and safely achieve top speed to check the flyweight for your 8000 "tach" rpm. If you have too much flyweight, then the engine will start to lay down, the rpms will lower at/or near your highest speed. If so, just take a few 10ths of a gram out at a time.

The exercise:
Buddy trial the sled with 19 grams and still had the zoomies. HOWEVER, he lost less rpms.
He would run part throttle at 8000, and then under full throttle the engine would Zoomie at 7700-7800 rpms.
He returned and added 2 grams for a total of 21 grams of flyweight.

Buddy called his tuner pal at work yelling in his ear of how good the sled run. Keeping the clicker the same position all the way thru the exercises, he chose to keep adding the weight to load the engine.
The flyweight loaded the engine hard enough to heat the exhaust pipe while the engine accelerated, the pipe stays hot and the combustion chamber now heats up to make even more power. No more zoomies, now just kicking other sleds butts.

Belt Deflection and Height

When I work on Stock or Modified sleds, I take care of details in this order...
1] Secondary Belt Height:
I like to have the chord of the belt showing on the outer dia of the secondary.  If you look at the actual belt travel...The distance the belt travels towards the center from the clutch being closed to fully open, the belt travels only 1.25 inches approximately. So to think of it, if you have the capacity to go from 0mph to 100mph...The belt only travels that range of 1.25" in 100mph at 1:1 ratio. Would you not think that you would rather have approx 2mm of belt showing on secondary? 2mm=.080" Now you have ~1.30" to 1.33" of travel instead of ~1.25"
Benefits are:
i] 10% more belt movement from the engagement to top end.
ii] Extra time the belt can spend in the lowest ratio possible in the first 100 feet when you gas on it.

2] Best Belt Deflection = Track Movement:
Lift the sled onto track stand, start the sled, warm the engine up, burp the engine to turn the track, get the track nice and limber, getting the "cold" out of the track and loosen it up. When the sled is on a track stand and the engine started and idling, the track should:
i] Creep slowly or   ii] Turn with jerking movements or   iii] Track is still, but you are able to move it with by pinching a paddle with index finger and thumb then pull the track around fairly easy. You should now already have proper belt height on secondary. You must get the right belt deflection.  If you cannot get this kind of deflection, change drive belt to one that fits with proper length.  Be satisfied with that belt then.  When buying a belt, take a "Seamstress" measure tape with you and measure the belt circumference.  If a parts person gives you a hard time over it, Tell him "Go to hell, It's your money!" The results are very important.   You will be quite happy in the end.   Your sled will never bog with these conditions. You have found that your track moves on the stand at idle?  Great.   As long as your track moves or needs just a bit of coaxing with two fingers, you have great belt deflection.

Effects of Improper Belt deflection:
Too TIGHT of deflection:    i]Burns the belt cogs when sitting near engagement.    ii]Increases Torque at holeshot, but Hi-end mph is down.
Too LOOSE of deflection:    i]Bad holeshot, possibly bog.    ii]Slow In midrange    iii]Possible higher mph in midrange only if engine does not pull off peak[Old speed run trick]    iv]Engine pulls down out near big end.

Note: High engagement will eliminate bog, but acceleration deteriorates quickly by 2/3 track distance then 90% of time, engine falls low of peak rpm way out there.

Belt clearance: Prefer to have .025" to .030" on the primary. Tight belt clearance lets the tuner have better control of engine flashing thru the clutches. Tight is good for belts and will let them last a long "consistant" life.

TRA Ramp Thickness and Angles.

Shooting the breeze on TRA ramp thickness and the relationship of force the flyweight has with ramps that are thick and ramps that are thin.
If you have a Skidoo manual with the clutching pages that show all the TRA ramp profiles this will be easy to follow.
With the ramp pages open take a look at the 284 ramp. See how thick it is?
Now go back a page and look at the 144 ramp. See how thin it is?

With the 284 ramp, and the thickness it has, it holds the TRA arm closer to the clutch shaft center than the 144.
Because the TRA arm is tucked close to the clutch shaft, for whatever mass of flyweight[pinweight] you have in the arm, the engine has to produce more rpms to create enough force for the flyweight to start to push the clutch closed.
Lets leave the same mass of flyweight in the TRA arm and just change the ramp. Neglect the profile "steep & flat" of the ramp. Analyze the distance farther away the TRA arm is from the clutch shaft. Being the pin mass is farther away from the clutch shaft, the engine now can produce less rpm to start to push the clutch closed.
The engine induces less rpm with the 144 "thin" ramp to produce the same force as the thick 284 ramp at higher rpms.
The thick ramp holding the TRA arm close to the clutch shaft will deliver a "revvy" feel to throttle position.
You will make the engine rev high before the sled starts to move with any substantial acceleration or speed.
The thin ramp holding the TRA arm farther away from the clutch shaft will deliver a more "torque" feel. The feel is as if there is a larger engine under the hood. The engine can induce less rpm to move the sled. You use more of the "meat" of the torque curve from the engine as you roll on the throttle.

Ramp angles.
Now we can analyze the "steeper hill" "flatter hill" detail with a good example of the ramps 145 & 228.
The 228 ramp is made from a 145.
Many tuners know that the 145 has a higher engagement over the 228. The similarity is after engagement the roller going into the shift path, the roller shifts with the same force through the shift range to the end of the ramp as the 228.
The rest of the 145 roller path provides the same angles, same hill for the roller to follow as the 228.
The 228 has the flatter angle at the engagement area of the ramp than the 145. The engine induces less rpm to provide force to push the clutch closed at the beginning of the shift.
The 145 has a slight hill for the roller to overcome. So how does the roller get up this hill and over it onto the flat part of the ramp?....Induce more rpm.
Here is an unsophisticated analogy:
i]Your kid's wagon is sitting on the road. You push the wagon by hand with little effort so the front tire goes over the flat of the curb and travels into the driveway. [228]
ii]Your kid's wagon is sitting on the road. You push the wagon by hand so the front wheel has to go over a small wedge before the wheel can travel into the driveway. Oh...ramp you must go over? Can't do it unless you provide more force to overcome the angle of the wedge. Induce more force, now the wheel can travel into the driveway.[145]

Tuning For a Straight Shift

This is directed at TRA clutches.
Some tuners change a helix to one with a lower finish angle and they get climbing rpms.
Some tuners change a clicker # to a higher number and they get climbing rpms.

Does the engine run with a straight shift on clicker #2?
My definition of 'Straight shift' is the rpms maintaining a certain rpm from bottom end to top end?

On the initial setup, some tuners with a clutch setup have not had a straight shift which resulted in climbing rpms in clicker #2 or #3.
My definition of 'climbing rpms' is "The engine rpms climbing with a range of rpms that indicate the extent or perception of the capacity of their engine fitness or clutch setup."

I have had guys get climbing rpms in clicker #3 and asked them to run in clicker #2, however compensate for low rpms by pulling slight flyweight out to achieve the straight shift.

I have had guys get climbing rpms in clicker #2 and asked them to run in clicker #3, however add slight flyweight to get a straight shift.

Here at this point a tuner can or should adjust with about 4 tenths of a gram at a time.
You can adjust the flyweight by shaving the end of a setscrew. 3 threads shaved off on a 1/4 x 28 UNF screw is about 0.4 grams.
Taking the time to adjust the flyweight for top end with small increments as such, it's fun to do and there will be benefits to performing the exercise with this detail for hitting the flyweight mass spot-on for your engines requirements.


Another method to achieve straight shift with RER compression style secondary spring.
For lack of better numbers, if you have the black secondary spring [160-300] and want increased rpms in the bottom end of the shift range, you can leave your clutching on the primary the way it is and simply change to a green secondary spring [180-300].
Previously you had climbing rpms from 78 to 8000 with a black secondary spring.
Now with the new spring calibration the rpms hit the number 8 and maintain 8K right to top end.
The green spring is stalling the shift from the primary making the engine produce more rpms before the primary starts to push again.

hmmm...I have to get "stalling" for a definition on this page too. he he 8)
The way I mention above about (finding the straightest shift) then (tailor the flyweight accordingly) is the way I calibrate, yet there are a few more ways to skin a cat. ...pardon the pun

Tuning Primary - Slight Overrev at Start of Shift - Lack of Full Shift

Q1]...  440 sled. Engage:5500 Peak RPM: Reaches 8700, drops to 8600 / 8550 as mph increase.
Primary mark: 1/4" from top of sheave. No full shift out. Belt residue on sheaves at engagement.
Secondary/helix mark: Looked "ok", but upon disassembly mark is interupted nearing full shift.
A1]...  Add slight more flyweight to make engine pull harder. 440 engine @ 8400 rpm peak.
Simple rule to remember..."Flyweight determines rpm" It is as simple as that.
Need more rpms, then reduce flyweight mass.
Need less rpms, then add slight flyweight mass.


Q2]...  Pulls hard on engagement. 2 to 3 second delay at WOT before you feel it shift hard. You can feel the secondary shift out slowly and hard during or after RPM drop. Feels crazy fast after secondary shifts. Feels faster then stock setting.
A2]...  You just proved what I said. Know what the shift delay is? My explanation for this event would be from knowing the secondary is torque sensing. You accelerate the engine and the engine runs over it's peak hp/rpm, the shift is stalled.
The torque diminishes and so does the upshift. The engine pulls back on proper rpm and the secondary reacts accordingly by upshifting with you clutching on the engine's hp peak. I would add slight more flyweight and reduce this "delay" to maximize acceleration off the bottom of the shift.
There could be an opportunity to try a helix with a larger start angle than you are presently using to capture more of the "meat" of the engine by making it push with lower improved rpms.

Q3]...  Still pulls hard on engagement. Not feeling the slow / hard shift-out @ WOT. WTF?!? Open side panels/belts wet. Wiped clutches and panels. Pipe and motor not very hot. Should have warmed it up for another 10 minutes. Primary still needs to climb another 1/4" for full shift.
A3]...  Lack of belt at top of primary then flyweight is too light and will not let tra arm push hard enough. Need more flyweight to push the primary closed an additional amount when nearing full shift.

Playing With Pretension

Q]...  I'm trying trying to figure out my secondary. I was at 28/26/22/20/18 lbs preload and getting 75 mph. With much frustration, I was at 4.8 grams of weight. I added to the arm and on c-5 18lbs got 91 mph on clicker #3.
I went back and added 0.5grams more to the pin and to clicker #5. Got 75mph? *sigh* Thats when I tried all the preloads.
I didn't know why I slowed down so much? For kicks I tried b-6 (16lbs) and I got 93mph on the long flats.

A]...  Lets break this down to an easy picture to look at.
Exercise 1
28 lbs./75 mph
26 lbs./75 mph
22 lbs./75 mph
20 lbs./75 mph
18 lbs./75 mph

Exercise 2
Added 4.8 grams of weight to the arm
18 lbs
91 mph
Clk#3

Exercise 3
Added .5 g for total of 5.3g
18 lbs.
Change to Clk #5
75mph

Exercise 4
5.3g
16 lbs.
93mph

Ex#2   You added flyweight and clicker down.    With the clicker down the tra arm will push much harder in midrange speeds to top end, pushing the secondary open. With the flyweight you added, the primary will push harder and push open the secondary to shift to higher speeds. You changed two details that have the effect of making the primary push harder than previous details.

Ex#3   You clicker up to #5.    The tra ramp provides a steeper angle hill for the TRA lever arm to climb. When clicking up and providing a steeper angle hill for the tra arm, you have to add more flyweight to the arm to increase the arm force to overcome the angle the arm has to climb. If the tuner does not add enough flyweight then the primary will not push the secondary open to make the shift higher in ratio. The secondary resists the push of the tra lever arm, the higher clicker number resists the push of the tra lever arm, the mph will be low.

Ex#4   You went from 18 lbs. down to 16 lbs.    You diminished the resisting force that the secondary can match to the push of the primary. Not changing the flyweight in the TRA arm, the secondary could not match the force coming from the primary and therefore be more easily opened to provide a higher shift ratio and attain a higher speed.

I don't really think your kit is different than mine. When I pulled off 92 mph I had my suspension on soft all the way around to reduce track angle and drag. The lake had wet hard snowpack on top for great slider lube. My secondary has 21 lbs of pretension, however I am running a 16.7 gram pin with around a gram added for a total of 17.5 "approx value" If I ran less flyweight, my speed would be lower than 92 mph. I am running 19:44 gears for which also lets the TRA arm have more of an effect like it is heavier in flyweight. I would have like to know the temperature of your secondary sheave faces on the exact same run with these pretensions.
i]  28 lbs. ii]  22 lbs. iii]  16 lbs.
I have done tests as such and always found when the mph was close, the secondary temperatures were higher with the lower pretensions.
I'll add that this is all fine to use 16 lbs and get the highest mph, however if you were to get into bumpy conditions whereas you could only go w.o.t. around 70+ mph, the backshift would be very slow and reveal low rpms. If the conditions were where the snow depth steadily increased    [ex: running up a river where snow gets deeper]    then you will find at one point the rpms still high and mph lowering to a point where you let off the fuel even slightly, the engine recovery to peak rpms will be slow if being able to recover at all. The secondary will not be able to compensate for the increased load the sled is driving on. If you were to stop and check the secondary temperature, the sheave face temps will be very high.

Tuning Primary

Q]...  I've been looking for some advice as i'm not knowing to the concept of clutching. I ordered and aftermarket secondary with "X" for parts installed for my 04 revX 800HO summit 151".
I'm wondering how I should setup my primary as it seems they want you to decrease weight in the primary...Said to drop 2~3 grams pin weight & probably go with a doo purple/blue spring which engages at lower rpm than stock spring.
ps...maybe your working on a clutch kit for this secondary?

A]...  I do not know where you will be riding and at what elevation. From my experience being out in Revelstoke testing my summit 800 HO kit, you will need to lower pinweight to get the rpms correct at high elevations of 5000 feet and +.

Simple rule to remember....
"Flyweight determines rpm"    It is as simple as that.
Need more rpms, then reduce flyweight mass.
Need less rpms, then add slight flyweight mass.

First I would recommend to find a clicker number that provides you with the straightest shift. Straight shift being this...
Might want to have a look here...Re "Straight shift" www.mxzx-revzone.com/iq.htm

The flow:
1]... Search for straight shift first using clicker adj. "Does not matter if rpms are high or low"
2]... Tune flyweight next.
If you want to change primary spring then do so after you complete exercises #1  &  #2.
If you change primary spring and have different results, you will quickly know what to do to tune into this new spring by following the flow of 1]  then  2].

Sorry I am not working on anything clutchwise other than Skidoo OEM products.
I already have a kit for the 800HO summit and commissioned it earlier this winter past.
It flatout rawks! Good luck with your aftermarket secondary.

Pretension vs helix angle.

Using the same secondary spring on a 36 deg helix vs a 46 deg helix.
Consider the distance in length that the roller/button path is and how much in degrees the sliding sheave rotates towards the back of the sled.

The secondary sheave opens more in degrees to full shift with a smaller angle helix than a large angle helix.
The secondary sheave on the 36 deg rotates clockwise more, therefore the [pre]tension is more at full open clutch with the 36 over the 46.

Example:
At full open using the 36 helix, the pretension on the secondary spring may take 28 lbs to hold the sheave open while using 16 lbs cracking pretension.
At full open using the 46 helix, the pretension on the secondary spring may take 22 lbs to hold the sheave open while using 16 lbs cracking pretension.
With the 46 helix, you rotate the secondary sheave less in degrees than the 36.

This is a factor that many sledders don't take into consideration or notice when going to a larger helix angle.
Less Tension = Less amplitude for backshift signal. [Slower engine flash thru the clutches]
How much "less force" does the spring apply back against the belt thru the clutches with the 46 vs the 36?...6 lbs just in tension.

This is only for wide open throttle applications...
By going to a larger spring with the larger helix, you can choose a secondary spring that will let you the tuner have the same pretension you like and still end up with forces "needed" at full open for the sheave to grip the belt efficiently as with the 36 deg helix.
The new spring with the 46 helix will indeed need more required force to compensate for the sideforce missing to keep peak rpms that the 36 provided.
New spring, you will have a better signal for the upshift with the 46 deg helix.
You will have to adjust the pretension to your satisfaction finding best mph.

Spring rate is constant relative to torque from the engine. The force is x amount at low shift ratio, and is x+ amount at higher shift ratios. If you took the helix out and just ran with the spring, it would only have a certain amount of sideforce and pretension to prevent the sheaves from opening. The torque applied "however much" will change how quickly the sheaves would open.

Side force that resists the sheaves opening up produced from the helix angle[s] is load dependant.
More load like deeper snow, the slower the sheaves will open. Less load like a flat surface, the sheaves will shift open quicker.
Highest loads like high speeds attained at full shift require very high sideforces to grip the belt and keep it from slipping.    [low contact patch the belt has at highest shift]    Neglect the spring, what would produce the best required sideforce to "maintain" highest speed/shift ratio?.....36 finish angle? or 46 finish angle?

Q]...  If you tighten up the secondary spring by one hole, your RPM will increase, right?
A]...  Not neccesarily. Yes you are adding more force to resist the push from the primary, since the spring rate is the same right to full pretension the rpms, you will find they will increase when you test and the shift ratios are higher, nevertheless the rpms will eventually increase and mph will be down.
Want to see higher rpms right from the get-go?...change to a spring with a higher rate. A spring with a higher finish force will do. A spring with a higher installed force and higher full shift force would be most satisfying your question.

If you can remember this definition of RATE...[How fast something happens] or better for our case [how much something changes per inch]
If you find a spring that has a higher rate, the rpms will be the same as the previous spring for a short time, but quickly increase in over rev. The compressed force has much more of an influence on raising rpms than pretension.
Have you not tried to do this exercise with different springs?


Q]...  a higher compressive rate (longer spring), installed in the same holes, your rpm's will also increase.
A]...  Not neccesarily. Don't look at a long spring and think that it is stronger than a shorter spring.
Example:
Two springs when sitting upright measure 5" high.
One spring has 5 coils
One spring has 6 coils
...both are 5" tall.
Given both have same wire diameter/steel composition...etc, which one would have more compressive force at full shift when compressed down to 2"?
Answer, the 5 coil spring would.

If you have a 5 coil secondary spring laying about, grab it and place the tangs in each hand. Now pretend you're strong enough to stretch that spring out so it is uncoiled into a straight rod. Pretty long rod now eh?
How long is it? For lack of better numbers, say it's about 25 inches long.
Now you have the 6 spring and perform the same exercise. The 6 coil stretched out is now a 30" long rod.
Which one would be easiest to bend into a "U" shape? The 6 coil, right? You have the rod held by it's ends with both hands, the rod is longer and easier for you to bend because of increased leverage.

Short rod, hard to bend. Long rod, easier to bend.
That is the action of the spring performing in your secondary.
Less coils = more force/belt clamp.
More coils = less force/belt clamp.

You can prove this easily enough by compressing the coil springs in a drill press, with the spring sitting on top of a bathroom scale. Simply measure both springs to coil bind by compressing the spring with the drill press. The spring that gives you more force reading on the scale will ideally give you more rpms.

...so now you can look at secondary springs differently. =)

Q]...  What situations or clutching problems would be best addressed by tightening up the secondary spring pretension?
A]...  From my experiences, when you find the engine is slow to climb back to peak rpms after you let off the fuel, then get back on it.

Q]...  and what problems would best be cured by installing a stronger spring?
A]...  Excessive HEAT! ! !
.....where does excessive heat come from?

Helix Angles & Shift Characters

Q]...  Torque sensitive, I understand that. Must have resistance in order to react and load up the engine.
A]...  The helix is the connection between the ground and engine. The helix compares the load values applied from the engine and the load values of resistance from the ground. The helix then compensates accordingly with its angle allowing the sheave to open and upshift when the load is greater from the engine...
Or
...The helix and spring make the sheave close up when the load from the ground is greater than the push from the engine. "Backshift"

Q]...  Tach numbers am I correct in wanting to keep the sled in the 7900-8100 range for optimum pull? Mainly for mid range and high end. Isn't this power band you want in order to have an efficient setup?
A]...  Generally lower than peak rpms are saved for use in drag racing. Some tuners tune at lower rpms, some tune at peak rpms. Just to make things easiest for trail, you want the engine to shift at its published power peak. Generally tachs read 150 rpm high, so if you have a 7850 engine, then you may want to shift on the tach at 8000 "tach rpms" I have seen 50 low at 8000 rpms to 250 high at 8000 rpms, generally 150 is average. If you have lower rpms than published, the torque can be high and the sled will accelerate nicely, however the top speed will lack because of loss of available hp.

Q]...  I was thinking along the lines of throttle response. When you chop the throttle out of a corner and the sled seems to hesitate just for a sec, I would think that it did not backshift fast enough.
A]...Throttle response is a good snapshot of how your clutch system is working. Lazy throttle response is usually from the secondary backshifting slower than it could or should.

Q]...  "If I need a helix angle for the speed I am going" than I present this question for you, A dual rate helix (ex 50/44) would be the better of both worlds. You said a 50 won't get you to 100 mph, but I would guess it would pull hard, then the second angle would kick in to allow the clutch to shift out and begin hitting the higher mph's.
A]...  First to answer about angle allowing the clutch to shift out, I agree that in heavier snow loads and/or bumps the lower angle helix number will provide more clamp on the belt, provide more sideforce to continue to shift to higher speeds. The lower angle compensates for the load coming from the ground. The correct flyweight will continue to push the secondary open even with the lower angle.

To comment on the helix in subject, the angles are not dual or step. The angles are full smooth progressive with infinite angles in between the 50 and 44 I mentioned.

The angles on a 50/44 would be having the button/roller start at 50 angle, then the button/roller progresses to 49, then 48, 47,46...ending and dwelling at 44 degrees. If top speed were attained then the button/roller would be at the 44 degree of the helix.

1]  With this 50/44 say at midrange speeds of 50mph the button/roller in the secondary would be between 48 and 47 degrees. If top speed were attained then the button/roller would dwell at the 44 degree of the helix.

2]   Another example say if you had a 54/40 then at 50 mph the button/roller would be at 48 or 47 or 46. If top speed were attained then the button/roller would dwell at the 40 degree of the helix.

3]   Another example a 54/37; At 50mph the button/roller would be at or between 47 and 44. If top speed were attained then the button/roller would dwell on the 37 degree of the helix.


Addendum:
Q]...  I was thinking along the lines of throttle response. When you chop the throttle out of a corner and the sled seems to hesitate just for a sec, I would think that it did not backshift fast enough.
A]...  Throttle response is a good snapshot of how your clutch system is working. Lazy throttle response is usually from the secondary backshifting slower than it could or should.
The questions I would think after this effect, "What caused this slow backshift?"

If you can remember this [The helix compares the load values applied from the engine and the load values of resistance from the ground. The helix then compensates accordingly with its angle allowing the sheave to open and upshift when the load is greater from the engine...
You know that at approximately this speed the button/roller is on "X" angle during the upshift and the engine responce was slow. What lower angle would let the engine climb back to its peak rpms quicker making the sled feel less lazy?
You could continue to think..."Is my helix angle low enough for the speed i'm going at in these conditions?" Could I have used a lower angle dwelling in this area?
Or

If you can remember this   {The helix and spring make the sheave close up when the load from the ground is greater than the push from the engine.} "Backshift"
You could continue to think..."Does my secondary pretension have enough lbs of force in torsion?"

More on Pretension

Q]...If I play with my clutches to get the right setup.   How do I know if I have too much secondary pretension? How does the sled act? Does the primary start to slip or what happens?

Q]...Pretension does a few things.
1] Can adjust the time it takes for engine to "Flash" through the clutches.
"Flash" for lack of better words in a drag racing discipline is the time it takes for the engine to go from engagement rpm to its peak rpm for the primary to start to push the secondary open.

So for example, say you engage at 5000 rpm...
Your peak is 8000 rpm.
When you depress trigger and thumb hits the bar, it is the time in 10th-seconds for the engine to climb from 5000 to 8000 rpm.  A playback tach is wonderful tool to record this particular event.

If you do tests at a certain pretension and measure the time in 10th-seconds for engine to flash, then on another exercise increase the pretension, the engine will go from 5 to 8 in less 10th-seconds.
If you use less pretension from your standard, then the engine will take more time in 10th-seconds to flash from 5 to 8.
The engine will labor more because you have less resistance from the secondary to hold back the push of the primary.

2] Pretension will make a difference in top mph speed on a test track where you have enough test room to get near full shift speeds.
Increasing pretension from a standard you have been using, you can benefit from making the sheaves CLAMP the belt harder when you are near full shift speeds.   The friction between the sheave and belt is improved.   The belt slips less and instead of losing speed due to heat, the secondary will capture Better the push from the primary to give you better top speed, to a point where pretension is practical for that application

Heat from secondary tells great stories.   In fact, heat is like a voice from the secondary telling the tuner that "I'm still not efficient enough to grab the belt" and yes belt slippage is inherent in the system.  Who cares?  It is what we have to deal with so make the heat as little as possible.
Now there are many arguments over this that the speed may decrease.   If you monitor the rpms and they are straight shifting, and the mph is down, then this is good.  What is the temperature of the secondary sheave faces?
To "capture" the mph lost, with a composite flyweight, using the nuts/bolts/washers, it is simple to move the c of g of the flyweight towards the tip by a 10th of a gram or so, maybe more.   With the TRA system you merely lower a clicker position to push out more force.  Each case is slightly different so you must create notes to monitor the events. Say you still want to use only the same mass of flyweight, but now only want to move the mass to make the primary push harder at the top end?  You will push the belt down just a little more which is only thousands of an inch to increase mph via moving the composites towards the tip of your flyweight or with a TRA, you lower the clicker #.

Your notes will tell you the direction to go.
You don’t take notes, you have no information, and you cannot make a calculated decision to predict the future.

Quoting Freddie "SUPERTUNER" Klies:
There is also fact that once pipe becomes hot, it is thermally efficient and will provide a possible hundred rpm more in hp at full shift speeds.  By the time the sled gets to full speed the exh pipe is incredibly hot and thermally efficient and with this rpm there is more peak power.
You can see then it is imperative to have CLAMP on the belt from the secondary sheaves when the belt is in the lowest position.  Pretension will capture this "extra rpm" that is created from the engine's exh pipe getting more thermal efficient.
...Racers with 440 race sleds can tell you this is factual because pipe is sensitive to heat.  Most tuners heat up the pipe very hot to get proper rpms in their racing discipline.

There are many scenarios and I can elaborate on many from all the exercises I have done in the past.  The only reason I can spew comments here is because I take notes and I convey notes.  Many or much from what I say is in concert of what feedback and conversations from tuners who talk to me with notes and we construct "next directions" to go.

Gearing and Clutch temperatures

Some tuners think gearing down is going backwards when it comes to all around performance and top speed.
Never backward at all when gearing down within a reasonable ratio for your personal application.
I constantly test sleds every weekend. Using a 440 rev, I recently had been playing with gearing again on this 1 mile straight stretch. 4" to 6" of snow, mild bumps.
With my 440 I used all these gear ratios and regardless of gear ratio, I could always do 81, 82mph.

[2.04] 21/43 = 81, 82 mph [geared for 89]
[2.15] 20/43 = 81, 82 mph [geared for 84]
[2.26] 19/43 = 81, 82 mph [geared for 80]
[2.31] 19/44 = 81, 82 mph [geared for 78] got into overdrive

These two we had to add about a gram of flyweight to push the secondary open to get my top end back.
[2.38] 18/43 = 81, 82 mph [geared for 76] got into overdrive
[2.44] 18/44 = 81, 82 mph [geared for 74] got into overdrive

My stock gear is 21/43, but I now choose 19/44 as the midrange is impressive, backshift is impressive and going through the hills, I catwalk the sled quite far going up and over the top of them.   I did acceleration tests against a new pro-x 440 chassis with a Stock 600 Pol engine installed.   The lower I went the better I did against it with matching it to top end quicker.   Each gear lower, we realized the secondary temperature was cooler.   Here it seems like the sled reaches a "governor" point where the limitation of speed is due to the outside temperature/ground/trail condition as per my 81,82 mph top end.

I tested with lower gears on the 800 last season with great success on the same straight stretch.   With the stock 26:43 we could only get 94mph on radar.   Gearing down with 25, then to a 23 we still maintained 94 on radar on the same stretch having a moderate snow load.   Noticed midrange acceleration was stronger.   Recorded cooler secondary temperature with each lower gear.   [Don’t remember the degrees F.]

A B.M sled I did has 26:45 [1.57] thereabouts which should be geared for 1:1 at 111mph.   Making runs with it, it had scorching clutch temperatures.
The secondary temperature tells a lot, the temperature is the clutch[s] telling the tuner that I'm very "inefficient".   Being scorching hot 160 deg+ the belt is slipping in the secondary.   The belt will not go all the way up in the primary, as the secondary just does not open anymore.   How can it open, the sheaves are not clamping the belt anymore.
***The secondary does not open because the belt is slipping between the sheaves and will not push the sheaves open.***
I’m not a fan of changing the secondary spring to achieve belt grip at this point.   I would rather use a lower helix angle with an angle "required" to let the sheaves push back against the belt, clamping the belt harder.   If the belt can get clamped harder then the primary will continue to push the secondary open under w.o.t. and the engine rpms will probably not rise.   If a finish angle is chosen that does reveal rpms that climb this is fantastic for efficiency then.
Leaving everything the same we went down to 23:45 and recorded the same top end on the snow packed flying mile.
The owner found it hard to notice the increase in acceleration on the flats we tested on. However when going through this hill section where you are on and off the fuel, then returning to the start through a corner to corner point-shoot section, this then he was most impressed with the acceleration.   He never had that kind of ski lift from the sled before.

Great clutching will be like extracting 10+hp out of your engine and the proof is the secondary being cooler with realizing same-top-speed to higher top speeds that you want.   High temps is the Available-HP going up into the air, cooler secondary temps is Available-Hp going to the ground.
Gearing down can be beneficial for sure. Just need to look at the new symptoms, then use the theory you know to compensate for any irregularity that arises.
If you want to hold highest mph in snow, and I mean deep snow then gearing down will be most beneficial to maintain a high track mph.

I bet some here have found that when they geared up a tooth or two, their sled fell on it's face as if someone could grab the bumper and stop the sled from accelerating.

...Just my two cents.

MORE TOPICS TO COME