Horstman HDC-5 Clutch Manual

Foreword

The HDC-5A one disc model is designed for use on the Yamaha KT100 kart engine in Rookie/Jr Sportsman or Formula Y Jr class. The HDC-5B  2 disc model is for Jr or  Sr Sportsman or Super Can classes where rules permit.  This manual will help you obtain the correct setup for each class of competition.  

Warning!!!

When the engine starts the clutch and chain may spin at high speeds if brake is not applied.  Do not operate vehicle without proper guards in place. Do not attempt to adjust, repair, or lubricate clutch or chain with engine running.  The cerametallic friction disc has a very aggressive lock up.  When leaving the grid to enter track it is possible to have clutch chatter however it that will not affect performance on the racetrack.

Installation

1. Install spacer with chamfer facing engine  (See Figure 1)                                                      Figure 1

2. Apply thin coat of grease to the bearing in the drum

3. Slide drum onto crankshaft…sprocket faces engine

4. Insert woodruff key into crankshaft

5. Slide the drive hub assembly onto tapered area of crankshaft.

    Make sure the keyway in the drive hub is aligned with the

    woodruff key in the crank. Rotate the drum to allow the outer

    lugs of the friction disc to align with the slots in the drum.

6. Install starter nut (item 15) Torque to 350 inch lbs

    The optional spanner wrench p/n 336062 is helpful in holding

    clutch during installation, removal, and disassembly. See Figure 2

7. Check end play (Figure 3)                                                                                             

8. Install chain and clutch support system as required by rules.

End Play

Proper end play (clearance) allows the clutch to spin freely. Zero end play will not allow the engine to start. Check end play with feeler gauge. Measure between sprocket and spacer. (Fig.3)  Minimum end play is .005” and maximum is .035”.  If end play is below .005” you must remove the clutch and grind or sand material from the spacer.  If end play is greater than maximum contact your dealer for purchase of a wider spacer.

¬ Figure 2     Figure 3 ®   

Stall Speed

Stall speed is the RPM that the clutch locks up solid. For top performance it is important to adjust the stall speed to match the peak torque of the engine. This allows the engine to operate within its power band for quicker acceleration.  Factors that affect stall speed such as metallurgy, friction material, lever design, and surface finish are engineered into the product therefore you only need to be concerned with proper springs and adjusting the spring tension.

Stall Speed Adjustment

Adjusting the stall speed of the clutch may be intimidating if you are a newcomer to the sport however it is relatively easy to learn. Data acquisition with memory is needed to log accurate data.  Setting the clutch stall speed to the engine’s peak torque should produce the fastest lap times.  If the stall speed is set more than 100 rpm above peak torque lap time may be slower and the clutch will run hot which causes excessive wear and possible warping.  Of course if the stall speed is below peak torque lap time may also be slower.

  page 1

   [Next Page]

[2]   [3]    [4]