<p>A drive mechanism 1 comprises a combustion engine 3 and a start system 5 which has an output 7 that is connected to a camshaft 9 of the combustion engine. The start system further includes a flywheel 11 and connecting means connecting the flywheel to the output. The connecting means comprise a clutch 13 and a gear reduction 15. The start system 5 further includes a drive source 17 formed by an electromotor which is directly connected to the flywheel 11 or which is connected to the connecting means between the clutch 13 and the flywheel 11. The maximum power that can be delivered by the drive source 17 is just sufficient to maintain the flywheel at the proper r.p.m. If the drive source 17 is turned on, it thus delivers just sufficient power to maintain the flywheel at the proper r.p.m. The maximum power of the drive source is in this case 50 W.</p>