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Get Ready to get awesome starts with great reliability in the Junior 1 Classes. Our Junior 1 Rock Star Clutch is a two disc clutch for both Animals and Flathead classes.
Thank you for purchasing the Junior 1 Rock Star Clutch. Years of research and development have gone into building this innovative new clutch, which rivals any in the market place. Following is critical information on proper use of your new Rock Star clutch which will help you to achieve the best level of performance. If you’re pro-active with maintenance, you will get long life from your new Rock Star Clutch.
The setup we found to work best for Junior 1 classes:
Purple Plate-3400 RPM -Spring height .220” measured with a dial caliper from the top of the gray lever plate to the bottom of the silver spring retainer . No weight on levers. This setup should give you an engagement of approximately 3400 RPM.
Clutch Setup Information:
In getting the optimum performance from your new Rock Star clutch, your stall speed or the RPM in which the clutch engages is critical. Depending on your engine builder and the peak torque of your engine and the RPM in which peak torque occurs, you may need to make adjustments. As a rule, you will want the RPM of engagement to be within 50 RPM of your peak torque RPM. How good your engine’s torque is plays a factor in what RPM your clutch will need to engage. Here is a general RPM guide by class:
To check your stall speed RPM, watch your tachometer as the driver is sitting in the kart. As the kart starts to move forward, check what the RPM is. That is the RPM in which your clutch will engage the drive sprocket and move the kart forward. As the springs are adjusted clockwise, the spring pressure is increased and the RPM is raised. To lower the RPM, turn the springs counter clockwise. When setting RPM, we suggest making adjustments in ¼ turn increments. After you get the perfect RPM, go check your spring height and make sure they are all within .004”. During this process, be careful to not over heat the clutch. Let the clutch cool completely in between tests of RPM.
Springs and Weights- Spring and weight combos can be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes and the lower the RPM of engagement. We have found that the Rock Star clutch works best in restricted classes when using the weight kit on each lever. Unrestricted classes use no weight.
Installation Instructions:
Take everything out of the box and make sure it is all there. You should have the clutch, instructions, a sticker, a bag with fasteners to secure the clutch to the engine and an illustrated replacement parts list. Before installing any clutch, inspect your seals and gaskets on the engine to make sure that there are no leaks that can cause your new clutch to be compromised. If there are any seal or gaskets leaks, this would be the time to make the repairs!
Slide the clutch onto the crankshaft of your engine. If the clutch does not slide on the crankshaft easily, sand the crankshaft until the clutch slides on properly. When installing the Rock Star clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the clutch will be much shorter if the clutch is installed with the sprocket outward.
Secure the clutch to the engine with the enclosed fasteners. First slide the clutch onto the engine. Then, slide the clutch key into the clutch when the clutch is lined up with the key slot on the crankshaft. Next, slide the lock washer on the bolt followed by the hardened beville washer. Tighten the bolt. The clutch is designed to move on the crankshaft up to 1/8 for proper chain alignment. If you are changing your drive sprocket before installing the clutch, make sure that there is no grease or oil in the drive sprocket that you are putting on to the clutch. Use Vaseline for clutch driver lubricant. Excessive lubricants on any kind will ruin any clutch. Make sure that your chain does not have excessive lubrication on it. Acceptable chain tension is about a ½ up and down movement.
Clutch Break-In
The Rock Star clutch discs need a period of break-in time in order to achieve the best performance and durability. The best way to achieve proper break-in is as follows: With the kart on the stand, run the engine. Operate the throttle with one hand and the brake with another. While slowly accelerating the engine, apply slight brake pressure. Do this for approximately 4 minutes. Shut the engine off and let it cool. After the clutch cools, repeat the same process again. You can also take some slow laps during open practice on the track. Do not abuse the clutch while using it for the first time. After each session, blow the clutch out with compressed air. It is also good to blow the clutch out on a regular basis. Rapid break-in may cause the clutch discs to wear prematurely.
Contamination
Contamination is one of the main culprits that cause clutches to wear prematurely. When certain chemicals get into the clutch and on the discs, the amount of friction is increased or decreased, causing the clutch to get either more friction or less. Either way, the result is heat that causes the clutch to wear rapidly. Oil, excessive moisture and dirt can all cause your clutch to live a short life. If your clutch becomes contaminated, you can replace the friction discs, floater and sand the pressure plate and backing plate. Clean the clutch with acetone.
Clutch Driver Lube-Use Vaseline for lubricant on your drivers. Even if it gets in the clutch, it won’t hurt it.
Chain Lube-Use small quantities on non-synthetic and non-Teflon based lubes. Make sure the lube does not sling into the clutch.
Every 4 to 5 races remove the clutch drum and clean the bearing. Use a very small amount of Vaseline to lubricate the Torrington bearing beneath the clutch basket.
Contamination can also cause premature wear and seizing of your clutch levers, making the clutch operate improperly. Inspect your levers to make sure there is no wear on the nose of the lever (bottom) that contacts the pressure plate. Also make sure that the levers pivot on the lever pins freely. Excessive moisture can cause the lever to seize to the pin. In the event this occurs, you will need to disassemble the clutch and polish the contamination off of the lever pins with Scotch Brite.
Air Gap
Air gap is the clearance between the friction discs and the clutch. It can be measured with a feeler gauge and is stated in thousandths of an inch. The Rock Star clutch air gap is set between .028” and .033” from the factory. Increasing air gap will cause the Rock Star to hit harder and cause less slip. In some cases, increased air gap will cause the engine to bog some. Try to keep your air gap in the range set at the factory. As clutch wears, air gap will increase. When air gap becomes excessive you can change to a thicker floater disc. This will restore the air gap back to the factory setting. You can also remove shims in order to get the proper air gap (later models).
Parts that wear
Of Course heat is huge factor in clutch wear. Be careful to not overheat the clutch. Excessive braking and throttle at the same time will destroy a clutch in no time. If you over heat the clutch, you will need to get it re-ground.
Friction Discs-Over time, the friction discs will wear. When the friction discs wear to .115” thickness, it is time to replace them. In some cases, the clutch will perform better with new discs even though they have not worn to the minimum thickness. If your clutch performance starts to decline, it may be time to replace the friction discs. This could also be the case if some contaminants have gotten onto the discs.
Floater Disc-Replace the floater disc every time your replace the friction discs. Also, replace the floater disc if it is warped or has signs of scarring or material transfer.
Springs-Your springs will lose pressure as they get heat cycled. Of course as the spring ages, you can always adjust the installed height to get the proper engagement RPM. You should replace the springs every other rebuild or if the engagement RPM drops on a regular basis.
Pressure Plate/Backing plate-These parts do not wear very much unless excessive heat is introduced.
Rebuilds
The life of your clutch is totally dependent on your maintenance and driving style. If you take care of the clutch, it will last a long time. The Rock Star clutch wears about the least of any clutch available. With a new clutch, we recommend that you send it back to Rock Star for regrinding at the first rebuild cycle. Rock Star utilizes precision high-end grinders in making your clutch surfaces totally flat and “square” with the rest of the components. The proper surface finish is also important in helping the clutch break-in properly. Using sub-standard re-machining equipment or procedures will not allow the clutch to perform as it was designed to.
Regrinding the clutch will make all the contact surfaces flat again causing the clutch to operate at optimum. After the first rebuild/clutch regrind, the clutch will last longer before subsequent rebuilds because the steel parts will have settled. Regrind costs are economical compared to buying a new clutch. Normal costs are $55 plus parts.
The number of races before rebuild is usually 10 to 15. If performance levels fall it is either time to replace the friction discs, or it is time for regrind and replacement of friction discs.
Make sure you use original Rock Star friction discs if you are rebuilding the clutch yourself. You can use other friction discs, but the Rock Star friction discs will give you the best performance level. Rock Star friction discs were designed from the ground up for the best compatibility and performance with the steel material in the clutch. We cannot be responsible for any damage or performance loss caused by using inferior replacement parts.
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