Repair 7

How to Run in a 2 Stroke Bike Engine

The two-stroke motorcycle engine is a contradiction. Despite their bare-bones mechanical simplicity, they tend to require far more attention to keep them performing than their larger brothers. Oil must be caully added to the fuel mixture in the correct proportions, and regular rebuilds are not uncommon. Following such a rebuild, it is advisable to complete a period of Running-In to ease the engine back into performing, without putting it under sudden strain. There are countless interpretations of how to do this, but several principles hold true across all of them.

Instructions

1

Start the bike, and allow it to idle for a few minutes until the engine is up to temperature. Do not lean the bike on its side stand, as this will cause the oil to collect in one side of the crank case. Use the center stand, or sit on the bike if it does not have one. Turn off the bike. An important characteristic of the running-in process is gradually increasing the periods of time for which the bike is running. Once it has cooled enough to touch, start it again.

2

Ride the machine for a short 5- to 10-minute run, keeping the throttle below 50 percent, and ensuring that all other components; brakes, shifting, steering, etc.; are all functioning OK. Return home, and allow the bike to cool down completely again. This will generally take at least 30 minutes, but the longer the better. You should be able to touch the pipes and radiator without feeling any residual heat.

3

Start the bike again, and head out for another ride. This time, the throttle can be pushed to 60 percent. After 10 to 15 minutes, return home again, and allow the bike to cool once more. Repeat this process another four times, increasing your throttle limit by 10 percent on each run, every time allowing the bike to cool down completely every time.

4

Ensure all fasteners are still fully tightened. Your two-stroke engine should now be ticking over smoothly. Allowing the engine to properly cool after each run helps small quantities of oil to act as a seal at the points where different components meet, reducing the possibility of damaging the pistons.