Algodoo

you gotta correct a lot of things

First don't use so much mass on the pistons, use 2-5 kg. otherwise you'll have vibration and the spin up time will be too much
For the flywheel use 20 kg or less, anything that would prevent stalls will work but 40 kg is too much
For the rods, make each of them weight more than 0.5 kg. 1 kg for each should be fine. Try with density 100 for them, that gives like 0.9 kg

Get rid of all restitution on the engine

Make the pistons reciprocate a little bit less and put them closer to the flywheel (get the rods to have 3/4 the height they had, so the engine is smaller)

Get rid of those hinges that connect the cylinder with the back of the engine (the 4 hinges) and use a fixate. never use axles as fixjoints. it's just nonsense and that will get you a lot more stability

And for God's sake use 200 Hz or less! Better weak than 1200Hz

If you do all that then use 6000 N/m and damping -1 on the springs and it will work perfectly

Another thing: use 10 kg for every gear and get rid of the restitution, also make the back wheel heavier so it doesn't dig into the ground