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Pitbike 4-Stroke Single Top End Assembly Guide

Important Considerations​

When assembling your Pitbike's 4-stroke single top end, consider the following expert tips:

  • Gasket Thickness: Some big bore kits feature head and base gaskets that are thinner than the standard ones. In such cases, refrain from using the stock "O" rings. Instead, apply a thin layer of Yamaha bond or Honda4 semi-drying adhesive for optimal sealing.

Flywheel and Camshaft Alignment​

  1. Flywheel Positioning: Set your flywheel to the "T" mark, indicating top dead center.
  2. Cam Sprocket Alignment: Align the top cam sprocket mark to the 9 o'clock position.

Valve Lash Adjustment​

  • KLX110, Honda 50-70, China 50-190, Daytona 190: Adjust the valve tappets to 0.003" for both intake and exhaust.

Race Heads & Camshafts​

  • Valve Lash Settings: Intake 0.003" & Exhaust 0.003". This gap between the valve tip and rocker tip is essential as it closes when the engine heats up.

Camshaft Installation​

For all applications:

  • Install the camshaft with the lobes facing downward or towards the piston. This initial step, combined with aligning the camshaft and crankshaft timing marks, ensures proper engine timing.

Additional Notes​

  • Cam Mounting: The 2-bolt cam mounting holes are offset drilled, allowing installation in only one orientation, preventing a 180-degree misalignment.

Torque Specifications​

  • 50-110cc Round Cam Cover Type & Honda 50/70 (6mm studs): Torque the head to 110 in/lbs, run for one heat cycle, then re-torque.
  • 125-150cc Round Cam Cover Type & Honda TRX90 (7mm studs): Torque the head to 140 in/lbs, run for one heat cycle, then re-torque.
  • KLX110 and KLX Head Type Motors (ZS155, 155HO, YX 150/160): Torque to 16 ft/lbs, run for one heat cycle, then re-torque 8mm studs.

Piston Alignment​

To determine the correct piston alignment side, refer to the image below:

Intake Valve Side