RK 400 clutch, Rotax clutch, clutch for Rotax C drive, centrifugal clutch for Rotax C drives.

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Centrifugal clutch for Rotax C gear box

No one will ever dispute the fact that a 2 cycle engine is not happy at very low RPM's with a large flywheel attached to its PTO end. The flywheel of course is the propeller.

This dissatisfaction is usually responded to with severe shaking and rough running. This action can be easily proven by simply removing your propeller from your gearbox and then start your engine.

You will notice that it hums like a sewing machine (kinda), well at least it's no longer trying to shake it's self off of the motor mount. The reason for this smoothness is due to the fact that the engine is not laboring to spin your propeller at idle RPM. Even with the propeller installed, the engine eventually will smooth out at around 2800 RPM.

The clutch assembly consist of two basic components. The Mechanism which is bolted to the end of the crankshaft and the Drum which is bolted to the gear box. The mechanism of the clutch contains a 4 pad/shoe assembly which is held retracted with two circular springs. These springs are tensioned to allow the pads to engage the drum at approx. 2350 RPM. Clutch engagement is very smooth and positive.

The need for a clutch in the Rotax gear box was originally developed for the airboat industry where zero thrust at engine idle was necessary, convenient and extremely helpful during docking procedures. It didn't take long for the ultralight owner to appreciate the smoothness offered by this system.

Material of construction is hardened steel. All steel components are precision machined and deep cadmium plated for superior corrosion protection.

The primary purpose of the clutch is to disengage the prop from the engine allowing it to start and operate at idle without vibration. When the engine is idling (below 2350 RPM) the prop is not turning.

Installation of the clutch replaces the gear box flywheel and the hardy disk.

Added weight is approx. 3 Lbs.
The clutch is only available in the "C" gearbox.

Centrifugal clutch for Rotax C gear box $530.00 U.S.  

RK 400 Clutch parts

RK400 Clutch for C drive

Clutch Assembly Clutch 530.00  
Adaptor Plate Clutch A 225.00  
M 10x6 allen head cap screws -3 RK 22 ea      .80  
Drum RK 33 203.00  
Drive body RK 44 248.00  
Spring - 2 RK 55 9.00  
Mechanism w/springs RK 66 140.00  
Retaining plate RK 77 60.00  
10x24 flat head screws - 4 RK 88 ea     .30  
RK400 clutch
  1. This unit is a must for float plane operators.
    Some of the benefits are the engine starts under no load, making the engine easy to start.
  2. Clutch does not engage until 2400 rpm - so when you start up on floats you are not propeller forward, or when docking it isn't pulling you where you don't want to go.
  3. The engine idles very smooth with literally no vibration.
  4. The unit weighs in at only 3 lbs.
  5. Quick installation

RK 400 clutch for Rotax C reduction drive.

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