Clutch kits - real world results?!?

[Turk]

I played with the stock clutching a bit & just raise engagement to about 4000 rpm. This is the best stock clutching I have ever seen from Yamaha. It might change when I get more miles & the temps get colder. Right now rpm,s are right in the meaty area on my Attak(10,000ish rpm)

 

[welterracer]

I wonder where the best place to remove weight from the stock weights would be.. (like they did at the races)

 

[Turk]

For racing & getting good top end on a 04 Warrior I removed the inner rivet. My 06 Attak is all stock clutching except a large shim to raise engagement & rpm,s are allmost perfect.

 

[welterracer]

Large shim where? In the secondary?

I added my moddified Helix from my warrior to my apex.. (same angle) for full shift out!

 

[Turk]

Engagement shims go in the primary clutch & just make the primary spring a little longer so the sled engages at a higher rpm.

 

[Bob Miller]

For racing & getting good top end on a 04 Warrior I removed the inner rivet. My 06 Attak is all stock clutching except a large shim to raise engagement & rpm,s are allmost perfect.

What kind of top end where you seeing by removing the inner weight on your Warrior? By removing that inner weight did that decrease performance in other areas?

 

[Turk]

The warrior stock clutching was underreving. By removing the inner rivet it brought rpm,s up to about 10,300 & reall increased performance.

 

[jminor1]

The warrior stock clutching was underreving. By removing the inner rivet it brought rpm,s up to about 10,300 & reall increased performance.

Would you assume it was underrevving from being a 136" as opposed to a 121" while still having the same clutching?

 

[dirkdiggler]

Turk how many studs do you run?

 

[Superstroker1]

Engagement shims go in the primary clutch & just make the primary spring a little longer so the sled engages at a higher rpm.

If the engagement spring you're reffering to is placed under the pressure spring in the primary clutch, the following will happen:

1- The primary spring becomes shorter @ installed neutral and becomes more compressed. In fact, the spring becomes shorter by the actual thickness of the shim you install.

2- The more spring shims you install, the higher the pre-tension @ installed neutral.

3- Since the tension has been increased by adding a spring shim, the engagement will increase, as long as you don't change anything else in the primary clutch (all things equal).

4- Installing a spring shim to increase engagement will reduce the side load on the belt @ actual engagement (the point where the movable sheave actually "initially" contacts the belt upon engagement) The reason for this is because the cam arm weight and or the mass balance along the weight has not been changed, so FORCE remains the same. If FORCE remains the same and the pressure spring "resistence" is increased by adding a pressure spring shim, the FORCE will be reduced upon engagement. Basically, this makes the cam arm react as if it had been lightened by a very small amount and the more shims you install, the more this amount increases.

5- This seems to be the most dificult thing for people to grasp. When you install a pressure spring shim or install a higher pre-tension pressure spring that has an equally higher full shift tension (old spring 120/260 new spring 140/280...exactly 20 lbs difference on bottom and top) THE RPM OF THE ENGINE WILL INCREASE EQUALLY at every point in the shift ratio, all the way to full shift. Another way to look at it is this; The engine RPM will be higher at the same GROUND SPEED for the sled, all the way to full shift.

6- Adding a spring shim raises RPM.

7- Adding too many spring shims could cause coil bind at full shift.

8- Adding spring shims may reduce the service life of your spring.

 

[fourload]

Engagement shims go in the primary clutch & just make the primary spring a little longer so the sled engages at a higher rpm.

If the engagement spring you're reffering to is placed under the pressure spring in the primary clutch, the following will happen:

1- The primary spring becomes shorter @ installed neutral and becomes more compressed. In fact, the spring becomes shorter by the actual thickness of the shim you install.

2- The more spring shims you install, the higher the pre-tension @ installed neutral.

3- Since the tension has been increased by adding a spring shim, the engagement will increase, as long as you don't change anything else in the primary clutch (all things equal).

4- Installing a spring shim to increase engagement will reduce the side load on the belt @ actual engagement (the point where the movable sheave actually "initially" contacts the belt upon engagement) The reason for this is because the cam arm weight and or the mass balance along the weight has not been changed, so FORCE remains the same. If FORCE remains the same and the pressure spring "resistence" is increased by adding a pressure spring shim, the FORCE will be reduced upon engagement. Basically, this makes the cam arm react as if it had been lightened by a very small amount and the more shims you install, the more this amount increases.

5- This seems to be the most dificult thing for people to grasp. When you install a pressure spring shim or install a higher pre-tension pressure spring that has an equally higher full shift tension (old spring 120/260 new spring 140/280...exactly 20 lbs difference on bottom and top) THE RPM OF THE ENGINE WILL INCREASE EQUALLY at every point in the shift ratio, all the way to full shift. Another way to look at it is this; The engine RPM will be higher at the same GROUND SPEED for the sled, all the way to full shift.

6- Adding a spring shim raises RPM.

7- Adding too many spring shims could cause coil bind at full shift.

8- Adding spring shims may reduce the service life of your spring.

I agree with everything except #5.Force of the weight=MASS OF THE WEIGHT MULTIPLIED BY ITS ROTATIONAL SPEED SQUARED.The extra RPM the spring gives you at engagement is much higher than it would be at full shift.It might be 200 extra rpm's an engagement but it is almost nothing at full shift.It kind of drops off proportionally.The profile of the weight and its weight distribution also play a role somewhat.

 

[Turk]

I don,t run studs. I will be doing some drag race testing on Wednesday against a ported SRX, piped vmax 4 & a Turbo Vmax 4(ya right...gonna have a hope in hell gainst either vmax!) & a piped 700 sx on a hard packes 1/2 mile track. I will compare stock; stock with aftermarket helix & a total clutch change with hh,s & post what I find. Gonna be about a 4-6 hour test session & hopefully have some pics. Gonna also try playing with different rpm,s to see what the actual sweet spot is.

 

[BlueByYou2000]

Allow me to set the record straight on my testing results.

1. I am a dealer for Simons CPR, Ulmer Racing, Maxximum performance, Mountain Performance and may others. The reason is because I like to offer my customers as much information as I can when it comes to spending money on go fast parts.

2. In my personal testing, stock for stock, my RTX is appx 1-2 lengths better than my brother in laws GT in 600 ft.

3. After installation of the Ulmer kit, my RTX puts 5-6 on the stock GT.

4. After installation of the CPR kit on my RTX it puts that same 5-6 on the GT.

5. After installation of the CPR kit on my RTX and the Ulmer kit on the GT, the RTX puts 1-2 on the GT.

6. Summary, BOTH KITS WORK EXCELLENT and perform amazingly similar. Testing will continue on both kits and both sleds.

For the record, the RTX does not have reverse and rider weight of the RTX was appx 15 lbs less. I can tell you I have installed alot of clutch components over the years and have never been dissapointed in anything that comes out of Jeff or Allens shop. Top notch tuners that sell products that work.

Also, I installed the CPR kit on my Dads Attak. Before the install he was getting run down by a Sabercat at about 80 MPH. Now, the Sabercat is no where to be seen at any speed. This sled absolutely destroys the Sabercat from Hole shot all the way to the top. I did the same with the Ulmer kit and found the same results. Both of these kits kick #*$&@.

You should also all check your drive belts. Alot of guys are over reving out there even in stock form. Take your secondary off and look at the jackshaft bearing, theres grease everywhere. Clean that grease out, wash your clutch sheaves with acetone and wash your belt with soap and water. Over reving can occur in a flash if even a tiny amount of grease/lube makes contact with the belt. Also, be sure to break your belt in properly. Put a good 15-20 miles on it before buzzing high RPMs. If you install a clutch kit without proper belt break in, your chances of woofing it are much higher seeing your putting more power through the belt...BBY

 

[rxwhopper]

i dont want to start nothin hear but i heard when they were doing some testing on some kits to run at old forge, yamaha tested all the kits by the top 5 yamaha go fast peaple and the yamaha stock clutching was faster, what i was told like others are saying on here, just lighten up the weights a bit till you hit the desired rpm and she flys.i heard this from a very good yamaha dude who works for yamaha, and i dont think he would b.s. me,i know hw asked one of the clutch kit vendors why his kit was slowere than the stock kit, and he said it was just a trail kit, but what is the stock clutching for? very good job on clutching yamaha, also for the record, you realize yamaha now has real trcks on the sleds they can clutch to, the old rubber bands they had yamaha was always tyrying to clutch not having to spin the track. now they have somethin to work wityh

 

[pro116]

I have also a sleds had kit's slow the sledf down until I started dealing with aulmer racing and simon's cpr there kit's are like others they actually work.