Yes, tall people can generally fit on TRON Lightcycle / Run at Magic Kingdom, but the "motorbike-style" seating can be quite restrictive for those with long legs or large calves. The standard "Lightcycle" vehicle requires you to lean forward and tuck your legs into a position where a "comfort bar" locks behind your calves. If you are very tall (e.g., over 6'4") or have a long torso, you may find the leaning position awkward, and those with larger lower bodies often find the calf restraints won't click into place. Disney anticipated this issue by including a "Test Seat" at the entrance of the attraction; it is highly recommended to try this before joining the virtual queue. If the standard cycle doesn't work for you, don't worry—most trains have a back-row "accessible" seat that is a traditional upright chair with a lap bar. You can simply request this "traditional carriage" from the Cast Member at the loading station to ensure a comfortable ride regardless of your height or build.