Petrol stihl pull cord pulls freely without engaging cog

There are a couple of things that could have happened, If it has been left with fuel and oil , and left lying against a wall or something else for a while, the combustion chamber may have gotten full of oil and the piston cannot move.

The cord may be overlapped and cracked the pulley and it got stuck there. The "dogs" broke on the flywheel cover and does not engage with the part where it rotates the engine.

Both of these require that you remove the flywheel cover and/or the spark plug. When you remove the spark plug check the chamber inside to see if there is no oil inside it.
The flywheel cover where the pull cord is located, has to be removed to check why it is not engaging or if it is stuck for some reason.

Sounds like the starter drive is jammed. Look for a large cog azt the back of the starter cord on the motor, manually push it in the opposite direction to the spin created when the cord is pulled.

Just take the cover bolts for the pull cord off. Then see if it works. There are usually two cogs that engage into the shaft of the engine. These cogs push outward when you pull the cord, engaging the shaft of the engine.

when you pull the cord the motion pulls out 2 pins that ingage the clutch. Some times when to much oil , dirt and wood dust gets in there it sticks. Some times I just clean it and the spring out and sometimes they are worn out

here are two videos on repairing the recoil starter rope for your mower




www.youtube.com/watch?v=Q3NjVomUQJM

www.youtube.com/watch?v=_m4iLN1Ao04

Are you sure the cogs on the pull start mechanism are actually engaging to turn the engine? Take off the belt cover and check that the front shaft turns when you pull. The cover is just behind the auger housing.

Unfortunately, disassembly of the unit will be required to diagnose and replace/ repair the malfunctioning starter recoil unit.

Pull cords are all pretty similar so if you've seen one then etc.....
Does the cord retract?
If it's a broken spring then the pull cord would not retract.
If it is retracting then it's probably dirt, grass clipping interfering with the spring loaded locking lever.
Either way the only way to be sure is to remove the top cover and inspect it visually and clean it out and spray some lubrication on it.
You should be able to do this without taking apart the actual cord and retracting coil spring. It should come off as a unit.

Once you have inspected it if you you have any other questions please let me know.
Hope this helps.

the recoil dawgs in the cover housing are either shot or not engaging into the top starter cone

try taking plug out to see if it turns then.if not take off pull cord assembley to see if something has come loose and jammed flywheel, failing that could possibly have snapped the piston ring and jammed. oh yes one last thing check clutch if you have chain brake on and clutch is jammed obviously wont turn.