KF3
OK-Junior is a kart racing class for top drivers aged 11 to 15.
This class used to be called Junior Intercontinental A and has changed since January 2007 when CIK-FIA decided to replace the 100 cc air-cooled two-stroke engines with 125 cc Touch-and-Go water-cooled two-stroke engines.The engines produce. The chassis and engines must be approved by the CIK-FIA. Minimum weight is 145 kg, including kart and driver.
Karts are equipped with an electric starter and clutch. The engine rpm is limited to 14,000 rpm.
It is one of the highest kart classes with national championships.
There is a European championship, a World Cup, as well as Oceania and Asia-Pacific championships. The Junior Monaco Kart Cup is taking place each year in this format.
For 2013 the class was renamed KF-Junior.
In 2016, the karts were completely re-designed by removing much of the electronics. The karts are now push started. The class was subsequently renamed OK-Junior, standing for Original Kart.
Champions
World
| Year | World Championship Winner | Chassis / Engine / Tires |
| 2013 |  Alessio Lorandi | Tony Kart / Parilla / LeCont |
| 2014 |  Enaam Ahmed | FA Kart / Vortex / Vega |
| 2015 |  Logan Sargeant | FA Kart / Vortex / LeCont |
| 2016 |  Victor Martins | Kosmic / Parilla / Vega |
| 2017 | Dexter Patterson | Exprit / TM / LeCont |
| 2018 | Victor Bernier | Kosmic / Parilla / Vega |
| 2019 |  Thomas ten Brinke | FA Kart / Vortex / LeCont |