Lenni Mäkinen first got behind the wheel of a kart at the age of four, and from that very first moment, he was hooked.

His karting journey began in a Puffo kart at the circuits of Hartola, Kotka, and Kouvola, where he learned the fundamentals of the sport under the guidance of his father. With patience and dedication, his father taught him racing lines, set up training cones around the circuit, and prepared the kart for every practice session.

Practice days often lasted much longer than planned. Lenni would hold tightly to the steering wheel and insist on staying out for "just two more laps"—a request that was almost impossible to refuse. That determination and passion for racing have remained the driving force behind his career ever since.

Lenni began racing competitively in 2019 at the age of six, entering the Cadet category in Finland's regional Kymi Cup and Pippo Cup championships. By 2020, he had already stepped up to national competition, travelling across Finland to race against the country's best young drivers.

His competitive mindset was obvious from the very beginning. He always wanted to be the fastest, make every overtake, and cross the finish line first.

While podium finishes became a regular occurrence, motorsport also taught him valuable lessons in resilience. Some disappointments came from his own mistakes, while others were caused by mechanical failures or racing incidents beyond his control. Every challenge became another opportunity to learn and improve.

In 2021, Lenni moved up to the Micro category and enjoyed a highly successful season, competing in 13 race weekends. Later that year, the family made a major decision to continue his development in Italy during the winter. In December, his mother drove the team's entire racing equipment to Northern Italy, where Lenni began training under five-time Karting World Champion Davide Foré. Throughout the winter of 2021–2022, he refined his driving skills while preparing for the move to the Mini category.

The 2022 season saw Lenni compete in the Raket Micro and Rotax Micro Max championships in Finland, while also racing in the Mini category in Italy. It proved to be an outstanding year, with an impressive 50% podium rate—12 podium finishes from 24 races in Finland. He also finished fourth overall in the Rotax Micro Max Championship against a field of more than 20 drivers.

The 2023 season marked Lenni's first full campaign in the Mini category. He competed in 22 national races in Finland alongside six race starts in Italy, taking part in both the Finnish Junior Championship and the IAME Series Finland. He finished sixth overall in the Finnish Junior Championship (6th of 20 drivers) and fourth overall in the IAME Series Finland (4th of 35 drivers). His impressive debut season was further recognised when he received the award for the fastest rookie of the championship.

The 2024 season followed a different approach. Rather than contesting full championship campaigns, Lenni focused on selected races in both the Italian and Finnish championships. At the beginning of the year, he made the important step up to the larger chassis and the OK-N Junior (OKNJ) category—one of the biggest milestones in a young kart driver's career.

Due to Finland's different age regulations, Lenni was not granted permission to move to the larger chassis a year earlier. As a result, his racing programme in Finland was limited to a handful of events with the smaller chassis, competing for Parolin Finland to maintain race sharpness while focusing on his international development.

Despite competing in a completely new category with unfamiliar equipment and without racing a full championship season, Lenni finished an impressive 23rd overall out of 95 drivers in the Italian Championship. He adapted quickly to the larger kart, and the cooperation with his team and mechanic proved to be an excellent match. By the end of the season, his pace consistently placed him among the front-runners, regularly fighting for top-five positions while continuing to gain valuable experience against one of the strongest fields in international karting.

For the 2025 season, Lenni focused entirely on the OK-N Junior category, with the majority of his racing taking place in Italy. Continuing his partnership with LA Motorsport, he competed in the Italian Championship, the WSK Championship, the Champions of the Future series, and the FIA Karting European Championship. The season represented another significant step forward in his ambition to reach the highest levels of international motorsport