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

[goosemasterkl]

bertsmobile1; how do I go about matching a coil with a flywheel? How do I test the stock/old coil to see if it's bad? Thanks

 

[StarTech]

On the old points briggs engines if you are fitting a modern coil with a chip, you have to turn it upside down .

That would be because the Briggs cast iron crankcase has a positive ground system. But it is worth that the aluminum crankcase are negative ground so if you put the coil on them upside down they will misfire due ignition timing. So the only time you need to flip the coil on an old Briggs engine would when a cast iron crankcase is involved.

It is also worth noting that at one time the cast iron cylinder block engine flywheels could be re-magnetized with the new polarity arraignment. As long the old coils are good it is easier just to install an universal ignitor set for the correct polarity.

 

[Mower King]

The position of the magnets looks the same don't they? It's an aftermarket coil; but the old one looks the same way.

I just wonder when people a going to learn, when you order aftermarket parts, there is a very good chance that what you order WILL NOT WORK. The aftermarket markets don't have the all the factory specs on ALL the parts.....there are too many different changes in parts. There can be 10 different parts for the same # piece of equipment and are specific to a certain model & serial #

 

[Fish]

I just wonder when people a going to learn, when you order aftermarket parts, there is a very good chance that what you order WILL NOT WORK. The aftermarket markets don't have the all the factory specs on ALL the parts.....there are too many different changes in parts. There can be 10 different parts for the same # piece of equipment and are specific to a certain model & serial #

That is why I posted this update, because there are not only different coils, but also the slot for the flywheel is in different versions of the crankshaft, etc....
Which is why I suggest putting the old coil and flywheel back on...

 

[goosemasterkl]

bertsmobile1; what did that tell you when I tested my flywheels with a magnet?

 

[bertsmobile1]

It told me they were not directly interchangeable unless the matching coil is also fitted.
If the new one is different from the old one then it is not a direct replacement for the old one & will require the matching coil.
The flywheel & coil work as a set .
I am not familiar enough with Stihl products to be any more specific.
As of late stihl have been marking their flywheels N & S to specify what the polarity should be.
I would assume that this was done because they had problems with coil polarity .

 

[PTmowerMech]

But just how does the batteries recharge and how many do needed during the cutting 3000' ft fence line 4'-10' on each side? I usually go through 1 to 2 gallons fuel mix per cutting along multiple refills of trimmer line.

That's when I'd break out something to kill the grass along that run. Unless I was in the grass cutting business.

 

[Spoken1609]

I'm working on a Stihl FS 38 trimmer that a friend said he couldn't get it started. I checked the compression and it had 90#. I then checked the spark and it was kinda eratic so I put a new coil and flywheel on it Finally getting a spark but still won't start. I then put on a new cylinder with new piston and rings now it has 120# of compression. But still won't start; doesn't even try to hit. I then put on a new carburetor; still nothing. It has kinda of backfired out the carburetor a couple times but that is as close as it gets to even making a sound of starting. It won't even hit using starting fluid. I'm stumped; I put everything on it new that I can think of. Somebody give me some ideas please. Thanks in advance to anyone who responds

Did you ever figure this out? I'm having same issue.. new carb.. new seals.. spark arestor clean. Acting like timing is of.. flywheel key ok.. tried new ignition..
I work on these daily and almost always have them up and running within 30 min max. I'm stumped...