Stihl MS 261 C-M

[gmacmopar]

Hi everyone, I've got a Stihl chainsaw MS 261 C-M the has no spark and will not fire. Changed the plug checked the wires everything looks good. Do you think I have a bad coil? What is the best way to check the coil?
Thanks hope I get some replies??

 

[bertsmobile1]

Remove the starter cover and remove all wires from the coil
If it then has a spark then the wiring / stop switch is bad
If no spark then the coil is bad
I use an orange spark tester in the dark because the spark is quite faint on a lot of these engines.
Note a flash = a pulse is being sent down the pug wire
You still need a good plug to make the spark.

 

[gmacmopar]

Thanks for the info!! I rechecked the coil again with a new spark plug and the same no spark. I then unhooked all the wires except the grnd wire and still no spark from the coil. I then put my meter on the switch wires there is a blk and a red and a grnd.I checked for continuity on the switch and I had it just on the red wire grounded to the ground wire. But nothing on the black wire which I presume is the feed wire? I then checked ohms on the coil and with the setting of 2000 I got 1.8 so what now? A new coil?? If so how much are they and does anybody have the correct part number for this coil to fit this saw? The numbers on the coil are1141 4701 B SMT 1745 does this help?

Thanks bertsmobile!

 

[StarTech]

It is one these coils but your local should be able to narrow to correct one after he reads the reference service bulletins.

 

[gmacmopar]

Thanks StarTech I will go down to the Stihl shop tomorrow when it opens up!!

 

[gmacmopar]

Well is there anything else I need to check to see why I don't have spark? If there is please chime in and let me know I'm open to any kind of advice?

Thanks

 

[Fish]

Are you using a drill to rotate the flywheel on your tests?

 

[gmacmopar]

No I I just crank it over with the starter rope first and then I unhooked the wires from the coil and replaced the cover and pulled it again no spark either time with a new plug

 

[Fish]

Is the side of the plug grounded on the block?

 

[bertsmobile1]

The spark from a magneto is proportional to the speed the magnets pass the coil and the intensity of the magnetic field
At cranking speeds a lot of magnetos put out such a small spark they are just barely visible in a very dark room which is why I use the orange glowing in line spark testers.
The other reason is if the plug is bad & tracking down the electrode you will still see the dim flash . Even then some times I can only get a result by forcing the tester between the engine fins.
It is very easy to miss the flash as it is tiny at cranking speeds so before I pronounce one dead I run it on my high speed mains power drill at 2600 rpm which is around idle speed for most hand helds
As the magnet strength decreases so does the voltage produced and the time taken gets longer so the spark retards
Thus some times a week magneto can be used by reducing the air gap
Inside the coil is a Hall Effect trigger that has resistors & transistors in it so a direct Ω measurement is meaningless except for the secondary windings ( coil ground to plug cap
In 11 years only one chainsaw has a bad secondary but it does happen,