Chainsaw Repair

Can you tell us what Model Stihl you are referring to.   That would help. 

As the magnets in the flywheel pass by the ignition module it will build up a magnetic field and then collapse.   When it does it will induce a voltage in the coil of the ignition module and will turn to a spark.  It is a type of magneto.   There are other solid state devices in the ignition module like a steering diode, capacitor, and I believe an SCR.  I do not remember all with out looking at a schematic.   

The flywheel I believe is turning CCW so by moving the flywheel from its keyed position CCW will advance the timing.   Even though this process starts before top dead center the actual spark does not occur until after top dead center or else you could have pre-ignition.   Also the saw would be hard to turn over and would kick back when pulling the rope. 

The gap between flywheel and ignition module is critical and most people here including myself use a business card for setting up that gap.   To wide of a gap could mean a weak spark. 

The fly wheel should be keyed to a fixed position on the crank.    It could be possible if the magnet on the flywheel is weak it would create a weak spark but I have never personally seen that happen. 

One other thing to check is compression.   To low and it will not start or run.    Air, Fuel, Spark, and Compression.   

One of the first things I always do to check a saw is to pour a little fuel mix down the carburetor while holding the throttle wide open.   Pull it over and it should at least fire off a couple of times.    That will tell you it has good spark, good compression, and that the fuel is going from the crankcase up to the combustion chamber. 

I looked at the parts diagram for the TS400 I do not believe there are any points.   It is all solid state in the ignition module.   
One other thing to look at.   Set the gap for the spark plug at .025 gap.   Saws run better with that gap.   

What I would do is to set the spark plug gap at .025 take it out of the saw and hold it sideways on top of the cylinder with the plug wire attached.
Then turn it over and see if you have spark.   It will be easy to turn over without compression and the plug will be grounded to the cylinder so you do not have to worry about shock.   

Part one of the above is points type and part 2 covers solid state ignitions .

I've got the theory of operation of the self advancing coils used on the 042 and 048 Stihl models which is a little more complicated .I may be mistaken but I think it works similar to a Briggs and Stratton self advancing coil .Unfortunately I don't think I can copy and submit that info .I'll delve into it though .