A worn piston ring can add 1 to 2 seconds to your lap times.
Generally, a piston ring that is less than eight hours old will not result in insignificant lap time drop off. As the piston ring wears, the edges become worn and rounded, and the contact surfaces become scratched. Some of the combustion gases escape past the ring – robbing you of valuable power. A worn ring will also reduce the internal vacuum which is important for fuel delivery.
Racers generally have their engines serviced every eight hours. The ring and gaskets are replaced and the piston is checked for any signs of abnormal wear or damage. Weekend warriors might put 20 or more hours on a top end. Engine failure, however, increases with hours.
Cylinder hone marks provide critical lubrication to the piston and ring. As the cylinder hone marks wear away, the piston and ring wear increases quicker. Putting a new ring and piston in a cylinder that is worn is pointless.
Cylinder honing requires specialized equipment to achieve the correct angles and hone depth. Incorrect honing will result in quicker wear of the piston and ring. Engine is a Nikalsil bore require a diamond hone.
Cylinders should be serviced every 16 hours (depending on engine and other factors). This is done as part of a top-end service. The following are replaced – piston, piston pin, cir-clips, gaskets, bearing. An experienced engine builder will also know, and correctly set, the port timing, piston to bore clearance, squish, ring gap, ignition timing for the type of engine, and track etc.
The main and conrod bearings and seals wear and will eventually impact lap times too. A worn bottom end can lead to incorrect air/fuel mixtures and also increase the chance of a catastrophic engine failure. The tolerance should be checked regularly. Generally, a bottom service is required between 20 and 60 hours (depending on engine and other factors). The top-end and carby is also serviced at the same time.
The parts used include those for the top-end and all bearings, con rod, gaskets, carby gaskets, fuel pump gaskets, fuel lines, spark plug, clutch bearing, gear oil etc.