You came here because you dont have flexible filament for the belt of the belt driven version ....Or you just love gears.... Nevermind, you will love this one!
In the thing files you will find all the specific parts for the gear-driven version that are different from the base model, the belt driven engine. Use the parts list on the assembly drawing (https://i.imgur.com/HDP7BVb.jpg) to find out which parts you will have to import from the other model.
All gears should spin freely. If they dont, slide them sideways on their mounting bolt until it gets better. Or print slower, in case the other method did not work.
If you dont have that particular electric motor, simply leave it and the starter_gear1. Or leave the starter motor entirely, as this version does not need it for the engine to work.
For all other information and instructions, please head over to the belt driven model!