Stihl FS 38 trimmer mystery!!!!!!!!!!

bertsmobile1; please try to explain it to a dumb old country boy where I might understand how to do what your suggesting. Thanks for the input.
 
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In Fish's photo you will notice the flywheel is marked N & S
So with a bar magnet the north end will be attracted to the south end of magnet in the flywheel and repelled by the north side of the magnet.
I have seen this once where the magnet in a flywheel was back to front.
A compass needle will point to the north side of the magnet .

When a magnet passes a coil you get a sine wave where the generated voltage goes from 0 to a peak then back through 0 to the inverse peak and back to 0
This can be 0 to +V to 0 to -V to 0 or the other way round - first then +.
However the timing chip is polarity sensitive so if it is for a + then - pulse and it gets a - then + puse it will not fire the coil
 
bertsmobile1; I appreciate your help but you might as well be trying to teach me algebra or some foreign language. I can't understand what you're trying to tell me. Thanks though; I really appreciate it.
 
goosemasterkl said:
bertsmobile1; I appreciate your help but you might as well be trying to teach me algebra or some foreign language. I can't understand what you're trying to tell me. Thanks though; I really appreciate it.
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Just hold any magnet firmly, and move it close to one magnet on the flywheel, then up to the other magnet. One time it will attract, the other time it will push away. Then, without changing the postion of the magnet in your hand, do the same thing to the other flywheel.
See if they attract/repel exactly the same, or do the opposite.
 
bertsmobile1; I couldn't stand it so I went out to the shop and did that test. On the stock flywheel the magnet to the right would attract my magnet and the magnet on the left would repel it. The new flywheel both magnets would attract my magnet. What does this mean; if anything?
 
I'm still curious about the crank seals, i would pour some brake fluid on them , let it sit for a bit,(it really puffs up old rubber) and try it.
 
It explains why you engine is not working.
The new flywheel is either magnetised wrong or it needs a matching coil
Trying to be as simple as possible
As the magnets passes the coil it generates a voltage that starts from 0 and goes either + or - to a maximum number ( number not important )
As the number gets bigger it causes the chip to close a circuit and the coil fires
If the chip is looking for a - number to fire but sees only a + number it won't fire the coil
Or it fires the coil at the wrong time.
I ran a fleet of SR 500 motorcycles and the magneto came with a matched control box & trigger and these items can not be mixed up or it would just not run correctly .
On the old points briggs engines if you are fitting a modern coil with a chip, you have to turn it upside down .

We now need an expert like Fish or Star to be able to confirm if your magnets are wrong and needs to be returned or what coil is needed to work with it.
 
bertsmobile1; when I checked those flywheels the stock one was off the engine on my work bench and the new one was on the engine crank; does that affect the test I did? Didn't know if both of them was supposed to be off or on the engine. Thanks
 
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