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Written by Vic R   



  • Do not over rev the engine during run-in period
  • Spend at least 30 minutes total running time at reduced revs


Process (without a tacho)


Start the engine and drive onto the track. During the first ten minutes of engine run in, the revs should be low, and below the engine power band.   The engine should feel sluggish and not want to accelerate quickly. It is normal for the engine to produce excessive smoke.     Under normal racing conditions, engine operate in the power band.  The engine will feel to have much more power when in the power band.


During the next 20 minutes, the engine revs can be raised slightly higher.  At the end of the run-in period (30 minutes), the engine can be fully revved but not before.


The accelerator pedal should either be fully depressed or fully released.  This will help load the engine and result in longer useful engine life.  It will also minimize buildup of oil on the spark plug and therefore minimize plug fouling.


At low revs, depress the accelerator pedal for about two seconds until the engine just reaches the bottom of the power band -  and wants to start accelerating freely.  At this point let the kart slow down to a slow pace again by fully releasing the accelerator pedal.  The brake can be used to help slow the kart down.  Repeat this process.


If the power band is reached, reduce revs.  Generally, you can fully depress the pedal in the tight corners but not on the straights.    


During the next 20 minutes of run in, fully depress the accelerator until the engine just enters the power band. Then allow the revs to slow again.   Repeat this process.


An engine that is over-revved during run-in will fail or result in a shortened lifespan.


Sometimes, the engine can be hard to start as a result of the run in process.  If this is the case, replace the spark plug.


Vic Roy

Engine Builder