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Centrifugal Clutches

Clutch Maintenance Info and Hardware


Max-Torque

Centrifugal Clutches

Max-Torque "SS" Centrifugal Clutches
with 3/16" Keyway - 3/4" or 5/8" Bore

Part Number

Description

Price

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04-455

CLUTCH 3/4"B 12TOOTH #35 CHAIN

39.50


04-457

CLUTCH 3/4"B 10TOOTH 40/41/420

39.50


04-456

CLUTCH 5/8"B 11TOOTH #35 CHAIN

39.50


04-458

CLUTCH 5/8"B 10TOOTH 40/41/420

39.50


Requires an engine crankshaft with a 3/16" keyway. 4" OD, Height 2-1/4".
The 10 tooth clutches use #40,41 or 420 chain. The 11 & 12 tooth use #35.
For most installations: Use a 5/16-24 x 3/4 bolt, a washer and a lock washer.
Grease the engine crankshaft and tapped hole for easier removal in the future.


The Classic "SS" (Six Shoe) Centrifugal Clutch: The "SS" Series is the most popular style centrifugal clutch used by American Go Kart Manufacturers since it's introduction in 1970. It has a broached 3/16" keyway with two set screw holes located 90 degrees apart. The two set screw holes are tapped 1/4"-28. The recommended key length is 1/2". The key and optional set screws are included. The secret to it's success is the ability to take heat without ruining the garter spring. The spring is made from 302 stainless steel and it can take more than twice the heat of music wire used by competitors. The Spring Manufacturer's Institute indicates a maximum temperature for music wire springs at 250 degrees F ... 550 degrees F for #302 stainless steel wire.

Clockwise or Counterclockwise - The Max-Torque Clutch will operate with equal efficiency in either a clockwise or counterclockwise rotation. The clutch can be mounted inboard or outboard with no adjustments needed.

No Load Starting - The standard Max-Torque "SS" automatic clutch is preset to engage at approximately 2,200 rpm. This engagement speed level protects the operator, as well as the power transmission system during engine cranking, starting and idling.

Max-Torque

Clutch Rebuild Kit

Max-Torque Rebuild Kit - Sprocket and Bushing

Part Number

Description

Price

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04-462

11 TOOTH 5/8" SHAFT #35 REBUIL

19.50


04-463

12 TOOTH 3/4" SHAFT #35 REBUIL

19.50


04-464

10 TOOTH 3/4" BORE #41 REBUILD

19.50


For Max Torque Brand Clutches Only
If you have a Max Torque Clutch, the name will be stamped on the back.

Bronze Bushings

Centrifugal Clutch Bushings

Part Number

Description

Price

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04-465

BRONZE BUSHING 3/4 BORE CLUTCH

5.50


04-466

BRONZE BUSHING 5/8 BORE CLUTCH

5.50


These bushings are an internal clutch part.
They fit inside the clutch, not directly on the engine crankshaft.
Bushing for 3/4" Bore - 7/8" ID .... Bushing for 5/8" Bore - 3/4" ID



Clutches Builtin Key

Clone Engine Clutches with a Built-In Key

Part Number

Description

Price

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G1011

CLUTCH 5/8"B 11 TOOTH 35 CHAIN

39.50


G1010

CLUTCH 3/4"B 10TOOTH 40/41/420

39.50


The G1010 Fits Honda and Clone Engines with a 3/4" crankshaft.
The key can not be removed and they do not use set screws. Requires
a 3/16" keyway that goes all the way out to the end of the crankshaft.
They will perform Clockwise or Counter-Clockwise. 4" OD, Height 2-1/4"


1

Comet SCS 400 Series 1" Bore Clutches
For 3-7hp Machines with Rear Tires 15" or Shorter

Part Number

Description

Chain

Price

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206169A

CLUTCH 1"B 12 TOOTH #35 CHAIN

#35

99.50


206170A

CLUTCH 1"B 10TOOTH #40/41/420C

40,41
420

99.50


These clutches require an engine crankshaft with a 1/4" keyway and a tapped end so you
can screw a bolt into the end of the crankshaft to hold the clutch on. Engages at 2000 RPM.



Comet Built In Key

Comet Clutches with a Built-In Key

Part Number

Description

Price

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209748A

CLUTCH 5/8"B 11TOOTH #35 CHAIN

39.50


209768A

CLUTCH 3/4"B 10TOOTH 40/41/420

39.50


The 5/8" bore 11 tooth is for #35 chain. The 3/4" bore 10 tooth is for 40,41 or 420 chain.
They do not use set screws. Requires a 3/16" keyway that goes all the way out to the
end of the crankshaft. Will perform Clockwise or Counter-Clockwise. 4" OD, Height 2-1/4"




Extreme Duty Clutch
Hilliard's Clutches

Hilliard's LD4S Extreme Duty
Centrifugal Clutches For 3/4" Crankshafts

Part Number

Description

Teeth

Price

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04-10389

CLUTCH EXTREME DUTY #35 CHAIN

12

68.50


12 tooth Clutch #04-10389 is also known as American Sportworks #12971

04-10390

CLUTCH EXTREME DUTY #40/41/420

10

68.50


10 tooth Clutch #04-10390 is also known as American Sportworks #12884

Hilliard Clutch Exploded View


The Extreme Duty Sprocket Centrifugal Clutch is ideal for the everyday demands of childrens yard-use go karts. This clutch was designed to be a low-cost upgrade to the stock unit. A thermodynamically designed clutch shoe increases the clutches capacity to absorb heat without damaging the clutch springs, resulting in longer life and better reliability.

All LD4S Series Clutches are loose assemblies and need to be assembled properly to allow the clutch to operate safely. These steps need to be followed to ensure proper installation. Install a bolt and washer on the end of the engine crankshaft. Use a washer that measures at least 1-1/16 inches on the outside diameter. On this LD4S-L long bushing series clutch there is a retaining ring to retain the bronze bearing in the sprocket drum. A bolt and washer are used to retain the hub on the crankshaft. Make sure that the bronze bushing has a minimum of 1/32 of an inch of movement on the crankshaft of the engine, and not more than 1/16. While tightening the bolt be sure to torque the bolt to the engine manufacturers specifications. To tighten the bolt you will need to make sure that the ignition is in the off position, to ensure that the engine won't start. Next, get the bolt tight to the point that you are turning over the motor while tightening the bolt. Then MAKE sure the ignition is off, and pull the pull starter just out far enough to catch the motor. Then continue to tighten the bolt to the proper specification, holding the pull starter out, you will feel the engine want to pull the started cord back in, you need to hold it out until you get the bolt tight. For cases where there is no pull starter, you will need to find a way to stop the crankshaft from turning over. Verify proper alignment of the sprockets and install the chain according to your owners manual. Over tightening the chain or having the chain too slack will cause premature sprocket and bushing wear. Oil the clutch bushing every 4 hours of use. Try to get the oil in between the housing and the bushing. Removal of the bushing from the sprocket is the best way to ensure proper lubrication.

Requires a tapped engine crankshaft so you can screw a bolt into the end of the shaft to hold the clutch on. The Extreme Duty Sprocket Centrifugal Clutch is ideal for the everyday demands of go karts and youth model snowmobiles. It has been engineered to provide long service life even in the most demanding applications. A thermodynamically designed clutch shoe increases the clutches capacity to absorb heat without damaging the clutch springs, resulting in longer life and better reliability. This Extreme Duty centrifugal clutch can handle higher temperatures to offer longer life. Bi-Directional, they can run clockwise or counter clockwise. Disapates heat better, extending clutch life. Built in internal key.


Hilliard Sprockets

Clutch Sprockets for 3/4 Bore
Hilliard's Extreme Duty Centrifugal Clutches

Part Number

Description

Chain

Price

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04-12466

10 TOOTH SPROCKET HILLIARD

40,41
420

22.50


04-12468

12 TOOTH SPROCKET HILLIARD

#35

22.50



Hilliard Bushing

Clutch Bushings for 3/4 Bore
Hilliard's Extreme Duty Centrifugal Clutches

Part Number

Description

Price

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04-12467

HILLIARD CLUTCH BUSHING 3/4 B

18.50




Max-Torque

Max Lube Clutches

3/4" Bore Max Lube Centrifugal Clutches

Part Number

Description

Chain Size

Price

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04-7680

CLUTCH MAX LUBE 12 TOOTH

#35 CHAIN

59.50


04-7681

CLUTCH MAX LUBE 10 TOOTH

#40,41,420

59.50


Includes the Zerk Bolt Kit #04-8489, shown below.


Max-Lube Clutches were developed in conjunction with Chuck Brister, a major kart manufacturer here in Louisiana, to address one of the most frequent problems with fun karts - lubrication of the clutch bushing. This lube system supplies lubrication directly to the clutch bushing through the keyway of the engine crankshaft utilizing a special zerkbolt fitting which is available only from Max-Torque. Since its introduction in 1992, lubrication problems have been dramatically reduced. Check to make sure your Briggs & Stratton or Tecumseh Engine has a drilled and tapped hole in the end of the crankshaft. The size of the hole should be 5/16" x 24 threads per inch. If your engine does not have this hole, the MAX-LUBE clutch can not be used.

Tools Required to Drill Crankshaft: Electric drill, 1/8" drill bit, ruler, hammer, center punch, 1/2" open end wrench.

Max-Torque Supplied Parts: Clutch with built-in key, 5/16" x 24 TPI zerkbolt and washer and two 3/4" diameter washers.

Installation Instructions: Examine the SIDE VIEW and TOP VIEW diagrams below. Remove the old clutch from the engine crankshaft. Disconnect the spark plug lead and slowly pull the starter handle until the crankshaft keyway is facing upward. Use a ruler to measure a point approximately 7/8" from the outboard end of the crankshaft to the center of the keyway. As shown in the diagram, the width of a nickel will also provide this dimension. Once this point is located use the center punch with a firm hit to make an indentation in the center of the crankshaft keyway. Drill a 1/8" hole at this indentation until the drill bit breaks through the crankshaft bolt hole cavity. Stop drilling. Blow out this 1/8" hole to remove any chips that might remain from the drilling operation. Place the two fibre washers onto the crankshaft, slide the clutch on the crankshaft and secure the clutch with the zerkbolt and washer.

CAUTION: Do not over-tighten the zerkbolt as the hex head will snap off. No more than 15 ft*lbs of torque should be used in tightening the bolt! Using a grease gun give the zerkbolt a full pump of grease. Replace the chain on the clutch sprocket and replace the chain guard.

Other Operating and Use Instructions: Grease the Zerkbolt, with one squirt, after each week of operation. Avoid or eliminate incorrect gearing. The gear ratio between the clutch sprocket and the drive sprocket should be 1 to 6. For example, if your kart has a 12 tooth clutch sprocket the drive sprocket should have 72 teeth. A 10 tooth clutch sprocket would require a 60 tooth drive sprocket. Tires with a diameter exceeding 15 inches tall should not be used. If any of these suggestions are not followed, the clutch will not operate properly and clutch life will be significantly reduced.

Lube System


Max-Torque

Zerk Bolt Kit

Zerk Bolt Kit for Max Lube Clutch

Part Number

Description

Price

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04-8489

GREASE ZERK BOLT ASSEMBLY

9.50


Grease Zerk Bolt Assy Fits Part #04-7680 & 04-7681



Max-Torque

Max-Torque Belt Drive Centrifugal Clutches

Part Number

Description

Price

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04-864

PULLEY CLUTCH 3/4 BORE

64.50


04-865

PULLEY CLUTCH 5/8 BORE

64.50


3.20" OD pulley that will accommodate either an A or B belt. Key included.




Comet Belt Clutch

Comet 1" Bore Belt Drive Centrifugal Clutches

Part Number

Description

Price

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202312A

PULLEY CLUTCH 1" BORE S350

89.50


3" OD, Uses A or B section belts, built-in 1/4" key.

Clutch Key

3/16" Clutch Keys

Part Number

Description

Length

Price

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8498

KEY 3/16" X 1/2"

1/2" Long

1.60


8454

KEY 3/16" X 3/4"

3/4" Long

1.80


8442

KEY 3/16" X 1-1/4"

1-1/4" Long

2.00


Key Stock

12" Long Sections of Keystock

Part Number

Description

Price

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04-5600

KEYSTOCK 3/16" X 12"

3.40


04-5601

KEYSTOCK 1/4" X 12"

3.80


Cut as needed. Use in keyways on crankshafts, jackshafts, pulleys, hubs, etc.



Max-Torque

Set Screws

Set Screws For Max Torque Clutches

Part Number

Description

Price

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02-119

SET SCREW

1.00


AS-1414F 1/4" set screw




Keep Your Machine Safe!

Centrifugal Clutch Maintenance


Oil the bushing that is located in the sprocket at least every two (2) hours of driving time. You'll have to oil the clutch even more often if you have small children, riding in a small area, never going fast enough to engage the clutch all the way. The clutch continues to generate heat until it engages.

Oiling the clutch is extremely important. If heat damage occurs, the clutch will never disengage and the machine will start taking off by itself as soon as you start the engine. This is very dangerous! You can see heat damage inside the clutch drum, the metal turns from black to a blue color. The clutch must be replaced if it has heat damage and won't disengage. Heat damage is never covered by warranty.

Where do you oil the clutch? Behind the snap ring, next to the sprocket teeth at the end of the clutch. There's an internal bronze bushing behind the snap ring that requires lubrication and it's up to you to put it there each time. With the engine off, squirt several drops of oil behind the snapring while the bushing is warm. You can also oil the clutch before you ride, oil the clutch and give the oil a few mintues to penetrate down into the bushing. If you don't give the oil time to get down onto the bushing, the oil will just fling off, which is the same as not oiling it at all because the oil never reaches the bushing at all. What oil should I use? A good automotive oil like 10W30 or a straight 30 weight oil is perfect. It's a good idea to oil the chain at the same time. If the chain gets kinky from lack of oil it should be replaced before it damages the clutch sprocket. A new chain is cheaper than a new clutch.

The clutch is an automatic transmission that is activated by the increased rpm of the engine. The clutch should not engage when the kart is at idle. The engine manufacturer sets the idle speed of an engine at the factory. The idle speed of the engine is normally around 1,650 rpm +/- 200 rpm. There are several things that can cause the clutch to engage at idle. Because the kart manufacturer does not start each kart after assembly, it's important that the dealer or the kart owner take a couple of minutes to read the owner's manual and review the recommended procedure when starting or servicing a new kart.

Throttle linkage can bend while riding or in transit to the dealer. It is highly recommended to always start the go kart with the rider sitting in the drivers seat with his or her foot on the brake pedal. MAKE SURE THEY KNOW WHICH PEDAL (the one on the left) IS THE BRAKE VERSUS THE GAS PEDAL!!! If the driver has to start his/her own kart then place the front end of the kart against a stationary object like a tree or fence post. Once in the kart, you can roll it backwards with your hand or foot to get the kart in a position to drive forward.

During assembly at the kart factory it is possible that too much tension was placed on the throttle linkage causing the engine to idle above 2,000 rpm (the starting speed of the clutch for engagement). THINK and STRESS SAFETY! When you start the go-kart, be in a position where you can shut it off if the clutch wants to engage by itself. Most karts have two shut off switches on them, one on the steering column and the other on the engine itself. A third possibility is to pull off the spark plug wire, which might give you a slight shock. If the clutch wants to engage by itself, turn off the motor, and verify what is causing the problem or bring it to a dealer that can correct the problem.

The dealer where you bought the go kart or a good lawnmower shop can put a tachometer on the engine to verify just where the engine idle speed is set. You cannot verify the correct rpm by listening to the engine and concluding it is too high or too low.


Some of the driving habits that can ruin a clutch are:


Driving too slowly: A clutch starts to engage around 2,000 rpm and will lock up around 2,600 rpm. Driving at full throttle gives the clutch a chance to cool down. Full throttle locks the shoes in the clutch against the drum. When the clutch is not locked up, the shoes slip against the drum causing tremendous heat which dries up the lubrication in the oil impregnated bushing. The tremendous amount of heat generated can also anneal the spring which is the heart of the clutch. If the shoes turn purple from excessive heat more than likely the clutch is ruined and the spring no longer has the ability to pull back the shoes at idle.

Short stop and go driving: The longer you drive at full throttle the better off it is for the clutch, because it gives it a chance to cool off before the next engagement.

Driving with the foot on the brake: This is a problem with new drivers that are unsure of themselves. When riding a go kart for the first time, try to find an open area that has no obstacles that you have to maneuver around until you get used to the brake and gas pedals. The driver must first be able to build up his or her confidence on the kart before putting obstacles in their path. A small back yard is not a good place to learn to drive a go kart. In my opinion, a minimum of three fourths of an acre is the amount of yard needed for a go kart. Teach your child to drive with one foot on the pedal, be it the brake or the gas but not to press on both pedals at the same time. You either want to go or to stop but you cannot do them both at the same time.

Changing the size of the tires: Putting on tires that are larger than what came with the kart will result in clutch problems. Tires exceeding 13 inches in diameter stress out a clutch if the kart is not properly geared for the larger tires. If you are driving on smooth flat terrain than you may be able to get by with 14 inch tires but once you get on hilly terrain, deep grass, then you are putting additional strain on the clutch, which will cause premature wear. Big tires look neat on a go kart but you create your own problem changing to a bigger tire when the clutch isn't designed to handle them.

Weight: A centrifugal clutch is designed to be able to move a certain amount of weight. Once the weight limit is exceeded, then the life of the clutch will be shortened. A good rule of thumb is the kart and driver (and passenger when it is a two seat kart) should not exceed 400 pounds. The kart weighs around 150 pounds add to this the driver (and passenger weight, if it is a two seater kart). If you know ahead of time that you will exceed the 400 pounds then buy a torque converter go kart and avoid the problems of burning up the clutch asking it to do more than it was designed for.

Gear ratio: The sprocket on the engine and the one on the rear axle should have a ratio close to 1:6. This means for every tooth on the clutch there are six teeth on the rear sprocket. So if you count 10 teeth on the clutch there should be 60 teeth on the rear sprocket. (12 teeth on the clutch means a 72 teeth rear sprocket). A torque converter has a variable speed system between the driver and the driven pulleys so it can improve upon this ratio, which gives the torque converter an advantage over a straight clutch system. It improves the ratio by approximately 3:1 and can turn larger tires and drive at slower speeds without doing any damage to the clutch system. A torque converter is a more expensive system initially but it will last longer and is more trouble free when maintained.

Restrictions: Don't try and reduce a go kart speed by limiting the travel of the gas pedal or by putting a restrictor in the carburetor to limit full rpm. Either of these methods will result in the clutch slipping, which is self destructive. A clutch needs full rpm to lock up as quickly as possible to be able to start to cool down. To slow down a go kart you would need to purchase a gear reduction unit, which is like training wheels on a go kart until the driver gets use to how the go kart handles. A gear reduction unit can reduce the speed of the go kart in half.

Keep the clutch and chain lubricated ...
Oiling the chain after it gets dried out is a waste of time.


Don't put oil inside the clutch holes: The holes on the drum are to let the hot air out of the clutch. DO NOT SQUIRT OIL IN THESE HOLES! When oil gets in the drum portion of the clutch it will cause excessive slippage, which means undue heat will be generated.

If your kart has a grease fitting in the crankshaft for lubrication then a shot of grease once a month should be sufficient lubrication. The grease is coming from the inside of the sprocket outward, which is a better way to lubricate the clutch. The keyway in the crankshaft acts as a reservoir for the grease, which cuts down on the frequency needed for maintenance compared to oiling the snap ring area. The chain still needs to be oiled frequently to keep it from kinking up. There are some excellent chain sprays available that are waxy and will not let sand and dirt adhere to them. Dirt and sand will wear the chain as well as the sprockets.

All chains stretch over time. When the chain starts falling off the sprocket then it is time to move the engine forward or backward to take up the slack in the stretched chain. There are four bolts that hold the engine on the motor mount plate. Take an open end wrench and a socket wrench (most likely a 9/16") and loosen the four bolts, pull back the engine until you take up the slop in the chain. Tighten the bolts back again but make sure the two sprockets are perfectly aligned with each other. You don't want the sprockets out of alignment because this will cause the chain to come off or wear the sprockets unevenly. Leave about half an inch of play between the top of the chain and the bottom, don't pull the engine back where the chain is a tight as you can get it. A tight chain can cause the kart to move in neutral with no one in the drivers seat. A tight chain puts friction on the bushing or roller bearing, which could cause it to engage when the engine is idling. A tight chain also wears out the sprocket teeth really fast.

Teach your child how to do the maintenance on the kart and accept responsibility for its upkeep. Every second tank of gas in the kart is about the interval for oiling the chain and the bushing.

Clutch warranty: How long will the clutch last? If it's installed on the engine crankshaft properly, without using the "magic hammer" to pound it on the shaft, using the right length key (half inch) and observing all the hints that are pointed out in this article, a clutch should last several years. But, if it's improperly installed, driven in abusive conditions (sand, steep terrain, excessive weight in the kart or rear tires taller than 15 inches), the clutch might only last 20 minutes. If the shoes are blued don't bother sending the clutch back for a warranty replacement. Heat damage is not a factory defect, it wasn't sold with blued shoes. If the clutch is abused, the tell tale signs are easy to spot. Go Karts with rear tires taller than 15 inches or an engine larger than 8 horsepower require a torque converter. If your kart has rear rims larger than 6 inches you'll have to install a Torque Converter that uses a belt and a chain. The last number of the tire size is the rim size.