September 11, 2007

Drive On



CPC’s ACT Diamond Drive clutch conversion kit

The new ACT Diamond Drive Conversion Kit manufactured by Cutler's Performance Center will transform any 2005 to present ACT driven clutch into a custom High Performance clutch. This is not just another clutch kit. This kit converts how the clutch works mechanically as well as providing and upgrading moving parts that have been precision CNC machined and providing new parts that recalibrate the driven clutch.

DRIVEN CLUTCH BASICS

Correct calibration of the driven clutch is essential for maximum efficiency. The most important concept for you to understand is the fact that the driven clutch is dominant over the drive clutch. The driven clutch is torque sensing while the drive clutch on the engine is RPM sensing. To improve efficiency or to change up shift or back shift characteristics, then adjust the driven clutch. If you want to change the RPM of the engine then adjust the weight of the cam arms in the drive clutch.

The purpose of the driven clutch is to sense a load on a snowmobile and keep the proper tension on the drive belt. Because the driven clutch can sense a load, the clutch must analyze how much torque it is receiving from the engine and compare it to the resistance it receives from the track. At that point it shifts to the highest possible ratio to obtain power and torque. When the load or resistance changes, the driven clutch will override the drive clutch and will shift up or down to maintain a constant RPM and deliver peek power out put. Both the drive and driven clutches work as a team and are dependent on each other. A change in one clutch will affect how the other clutch responds. One of the most important clutch tuning components is the driven clutch spring. The driven spring applies side pressure to the drive belt in conjunction with the driven helix. The driven spring is a key component to influence efficiency in the driven clutch. A lack of spring tension will allow the belt to slip in the driven clutch causing and extreme amount of heat. Heat is friction, an enemy to performance. Too much spring tension will cause a loss of efficiency and slow down acceleration. The goal is to have the correct spring tension in conjunction with the correct helix angle for the type of riding conditions (i.e. load or resistance on the track). Remember that a higher tension spring is required when a larger degree helix is installed. Higher degree helixes produce less side belt pressure because spring pressure is applied perpendicular to the sheaves rather than parallel to the driven clutch sheave.

The technology of this CPC driven clutch conversion kit, is dependent on two spring forces. This kit uses torsion spring forces that are applied by the twisting motion of the spring. Additional torsion force can be applied by changing the location of the spring tab in the holes of the cover plate. The second force is the compression force. This force is applied as the spring is compressed. Additional compression force can be applied by going to a larger diameter wire in the driven clutch spring or by going to a longer free length spring. The theory of changing to less spring pressure allows the belt to shift faster which puts more load on the engine and in return lowers the engine RPM. Just the opposite is true, when changing to more spring tension, the drive belt shifts slower allowing the engine RPM to increase.

The theory behind changing helix angles are simply this: A higher numerical helix degree allows the clutch sheaves to open faster allowing the belt to shift faster to a higher belt gear ratio. Lower degree angle slows the opening of the sheaves and allows the clutches to stay in low gear for a longer duration of time. Higher degree helixes have less side belt force due to the direction of spring pressure. On larger degree helixes, the spring pressure is applied perpendicular to the belt sheaves. On lower degree helixes, the spring pressure is applied more parallel to the belt sheaves. Lower degree helixes also influence better back shifting to a lower belt gear ratio due to more directly applied spring pressure in a parallel direction. This directly transmits to more side belt pressure and quicker back shifts. In reverse, larger degree helixes produce less side belt pressure due to spring force applied to more of a perpendicular direction. Less side belt pressure allows the driven clutch to up shift to a higher belt gear ratio.

Straight degree helixes are the simplest product to tune with. Most manufactures use straight degree helix for the use of stock snowmobiles. The use of compound helixes (An example would be a 44-38 degree helix) are an excellent way to take advantage of special riding conditions or to clutch the snowmobile to the match engine power and torque output characteristics such as turbo powered engines. CPC offers over 25 different compound helix choices and offer 13 different Turbo cut helixes to choose from. (An example of a Turbo helix would be 36-42 degree).

 

FEATURES         

1. Uses torsion spring technology.      

2. Uses quick-change helix technology.

3. Easy to work on design.

4. Uses low cost helix and springs.

5. Greater availably & selection of helix and springs.

6. Easy external roller replacement design.

7. Uses high quality CPC aero-space rollers.

BENEFITS

1. The use of torsion spring technology improves up shift (acceleration) and back shift.

2. Superior engineering allows for quick change of spring & helix in less than 2 minutes on the trail or in your garage without the use of special tools. Only a 10mm wrench is needed.

3. Uses modified OEM Arctic Cat helix & springs that were used from 1981 through 2007.

4. Rollers can be replaced in seconds without clutch disassembly with an Allen wrench. Rollers last longer because CPC uses aero-space high tech polymer plastic CNC machined rollers.

5. Increases belt life due to a decrease in belt heat.

6. Consistent clutch shifting characteristics due to higher lubricity and longer wearing rollers.

 

The proper way to tune a clutch is by choosing the correct spring and helix combination to give you the best overall performance. Then fine-tune your RPM by adding or subtracting weight from the cam arms in the drive clutch.

 

INSTRUCTIONS:

1. Remove driven clutch. Set driven clutch on a workbench with the backside facing up. Next disassemble driven clutch by heating the 9 screws with a butane or mapp gas torch for about 20 to 25 seconds each to loosen the thread locking compound, then remove each screw one at a time. Repeat the process by heating the next screw and remove it until all screws are removed. It the screw does not want to come out, try heating the screw a little longer. Disassembly is easier if you have a driven clutch compression tool or a second person to hold the clutch together until all the screws have been removed. Next, remove all the stock rollers and pins by taking a small punch and removing the roll pins by taping them from either side of the stationary sheave. Then take a ¼" drill bit and hand ream the inside of the ¼" hole that the roller pinhole is located in. A twisting motion of the drill bit will remove any burr that was created by the removal of the small retaining roll pins that you just removed. This is important or you will have a difficult time removing the ¼" precision ground pins that retain the stock rollers. These pins can be removed now by taking the small end of an Allen wrench and pushing on the 1/4 inch pin from the inside of the cavity and pushing the pin outwards. Old pins and rollers will not be used with this kit. Next using a clean cloth and acetone or brake cleaner, remove all dirt and belt deposits on clutch sheaves.

 

2. To assemble the driven clutch you will need only the following parts off the original clutch: The nine screws that held the helix onto the movable sheave, the small flat shim that are used between the helix and the movable sheave and the stationary sheave. If the screws get damaged from the removal process, you can purchase new screws from your Arctic Cat dealer using part# 1623-517. Next you will need to partially assemble the CPC conversion kit by installing the helix onto the three studs of the helix adapter and then slide the outside cover plate on to the studs and snug the three ny-lock nuts. The purpose of this step is to prevent the helix adapter towers to spread out when the nine screws are tightened into the helix adapter. Next using blue thread retaining compound (blue Loc-Tite) install the nine screws through the movable sheave, then through the round spacer shim that was originally under the stock helix, then into the helix adapter that is supplied by CPC.

 

Make sure that this bushing retainer shim is installed. If the shim is left out of the driven clutch, the movable bushing will work itself out and damage your clutch.

 

3. Slide the round aluminum torsion spring retainer over the center post on the stationary sheave. Install the three CPC rollers in the original roller cavities, then install the three stainless steel shoulder bolts to retain the rollers. The shoulder bolts will thread into the aluminum torsion spring retainer. Install all three shoulder bolts into the spring retainer before final tightening of the bolts to insure proper alignment before final torque is applied. Note: You will only use the three CPC rollers that are provided in this kit and they will be installed in every other roller cavity. See the photo below for correct roller cavity location.  

 

4. Next remove the three ny-lock nuts and then remove the cover plate and helix. Next assemble the stationary sheave into the movable sheave. You will need to make sure that the diamond symbol that is cast into the movable and stationary sheaves are aligned. If this is not done then your clutch will be out of balance. Then slide the helix over the three studs that are screwed to the helix adapter. The correct positioning of the helix is to have the three tips of the helix pointing down when installing the helix. Next, twist the stationary sheave to allow contact of the three rollers to the three surfaces of the helix. If the rollers don't match up with the helix, then remove the shoulder bolts and the rollers. Then install them in the correct cavity in order for the rollers to line up with the helix surface. See above photo.

 

5. Install the torsion spring into any one of the three holes in the torsion spring retainer. The three holes are machined at 120-degree locations in order to provide a perfect balance of your clutch.

 

6. Next, install the cover plate. The cover plate is drilled with three series of five holes. The purpose for the three sets of holes is to provide a perfect balance of the clutch and ease of installing the spring. Cutlers recommends that you start with installing the spring tab into the middle hole, then pre-load the spring by twisting the cover plate clockwise about 1/5 to 1/4 turn, then slide the cover plate over the three studs that are protruding out of the helix adapter. Apply downward force of the cover plate and at the same time install the three stainless steel ny-lock nuts onto the studs and tighten the nuts to seven to 10 ft-lbs of torque to tighten the nuts. Note: Never use an air impact gun to loosen or tighten the nuts on the cover plate or you will damage the studs and helix adapter. The CPC driven clutch assembly is now ready to install.

 

Modifying OEM Arctic Cat Helix

For those of you who want to modify Arctic Cat or any other aftermarket helix so it will fit into your new CPC conversion kit, you will need to perform two machining procedures. First take a 1/4 inch drill bit and ream the three existing holes. Second, you will need to chuck up the helix in a lathe and remove material to increase the entire inside diameter of the helix. The new inside diameter should be 3.225 inches. Now you are ready to install the helix.

Before you start tuning to calibrate either the drive or driven clutch, it is wise to check a few things to make sure you can take advantage of your new CPC clutch kit.

 A. Make sure both drive and driven clutches are clean and free of belt dust, grease or dirt.

B. Make sure that the rollers on the spider of the drive clutch are in good shape and that the cam arms and that the bushing in the movable sheave is in good shape.

C. Make sure that you have the correct offset on your clutch alignment. The correct tool to adjust clutch alignment for ACT diamond drives is Arctic Cat part # 0644-427.

D. CPC recommends using only genuine Arctic Cat belts. Make sure you start out with a new belt that is free from wear, heat check or stretch. It is impossible to get peak RPM or peak performance with a drive belt that is worn out.

E. After installing the driven clutch, make sure you have the correct belt deflection. Too much belt deflection will cause a bog as you accelerate from a dead stop. Too tight of belt deflection will cause the belt to squeak or the snowmobile to creep at an idle. It will eventually ruin the drive belt if the belt is run in this condition. CPC offers a belt deflection adjuster that can be installed to change belt deflection without changing the shims on your driven clutch.

F. Make sure your ACT diamond drive gear case has clean oil. CPC recommends that the oil be changed every 500 miles. Use only Arctic Cat synthetic chain case oil.

G. Re-evaluate your gearing for the type of riding or racing. Correct gearing will be determined by many factors including how fast of vehicle speed desired, rider weight, snow conditions, altitude, size of engine and type of terrain (flat or hill climbing).

 

For additional clutch information and education, you can order a CPC Clutch Tuning Handbook for $19.95 from Cutler’s Performance Center at (801) 224-5005 or www.cpcracing.com.








Hi-Performance Engineering, Inc
Bear Lodge Resort


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