You can reach the Motoworld by public transport in about 35min.
The line U6 direction Fröttmaning or Garching-Forschungszentrum is going from the south of the city through the city centre directly to Freimann. From there, it is a 600m walk to the Motorworld.
From the main station, you have 3 possibilities to get to the U6:
1. At main station, take one of the S-trains in direction Ostbahnhof. Change at Marienplatz stop in the U6.
2. At main station, take the U2 in direction Feldmoching or Messestadt Ost. Change at Sendlinger Tor in the U6.
3. At main station, take the U4 in direction Arabellapark. Change at Odeonsplatz in the U6.
Information on local public transport in Munich (MVV) is available at:
MVV JOURNEY PLANNER