You should normally follow the engine manufacturers instructions for assembling your engine, but here are some general points of good practice:
First, you should already have cleaned your entire engine before disassembly to prevent dirt and debris from entering the engine case.
Be sure all surfaces are clean and free from previous gasket material.
If your cylinder uses a power valve assembly:
Wash the cylinder carefully with detergent and hot water (not solvent), ensuring that all surfaces are clean and free of any loose material. Wipe the cylinder wall with the lubricating oil you presently use.
Power valve parts must be free from dirt, dust and carbon. When fitted into the cylinder they must operate freely. If they do not, remove the power valve part, identify the cause and if necessary relieve the obstruction with fine waterproof abrasive paper. Never force any part.
Ensure that the crankcase internal parts are perfectly clean since any debris, which has entered on disassembly, will probably be sucked into the cylinder and cause rapid wear to your new coating and piston.
Ensure that the piston to bore clearance and piston ring end gap is in accordance with manufacturer’s specifications. Allow ample ring end gap. There is far more danger of ring butting than an appreciable compression loss. Rings typically have a minimum of 0,3mm (0.012”) end gap in the cylinder bore unless the engine manufacturer or piston manufacturer has a different specification. Care should also be taken to ensure that the end gap can be closed properly around the locating pin if applicable. It should be noted that most manufacturer’s now offer pistons of varying sizes often graded “A”, “B” and “C” etc. please call us before assembly if in doubt.
Starting your engine
Follow the manufacturer’s instructions. If these are not available the following process should be used:
• Use the same 2-stroke oil mix as you normally use (if applicable). Do not use an extra rich oil mixture during running in.
• Allow 30 to 45 minutes for running in of the new piston, rings and plated bore.
• Allow the engine to cool down. Re-torque the cylinder head to factory specifications.
Race warm-up
• Air cooled engines normally require only a short warm up time prior to racing as long as the correct running in procedure has been followed.
• Liquid cooled engines should be brought to normal operating temperature prior to racing to avoid cold seizures. These result from the piston expanding faster than the liquid cooled cylinder bore.