Troublesome MS660

[dall]

i had the same problem on a fs55 changed carb fuel lines and coil still nothing so switched flywheel and still running they are a headache to diagnose

 

[TJ the Chainsaw Mechanic]

Well since you already gave away the issue, I'll say my guess anyhow. I was gonna be that redneck that said "Spark Plug?" LOL! Followed by, "Does it have a Champion plug?" Cause if it did...that would have been why it wouldn't start. lol

 

[treesmith]

I wonder if the stihl spark tester would show this up, think it should do

Sent from my SM-G900I using Tapatalk

 

[drf256]

I had this happen on an MS270/280. I still have the bad flywheel. I was working on 2 at once, switched flywheel by accident and said "WTF?" When I suddenly had spark with the same coil.

 

[CR888]

I wonder visually whether the magnet looked odd like blue or something.

 

[Mastermind]

I wonder visually whether the magnet looked odd like blue or something.

No, it was normal looking. I even sanded it to be sure the light rust wasnt a problem.

 

[Simondo]

I wonder if there could be a "Simple " test thought up to eliminate the flywheel magnet /s being bad or not....that would take you to the coil /plug lead or plug if the flywheel checked out.
Could using a high and low resistance plug (as per Randy did ) give a crude indication ? or has anyone got a plan ?

 

[Basher]

Any small magnet with a designated pole will tell immediately if a magnet in a flywheel has reversed polarity but it is much more difficult to tell if a magnet is just weakened. For a flywheel to work the magnets must be different polarity, usually they are positioned North first followed by South but not always and some flywheels have more than two magnets to make things more complicated. That is why some saws need the polarity of those chip switches like the Megafire wired up differently if the South magnet is positioned as the first magnet to approach the coil.

 

[Simondo]

Any small magnet with a designated pole will tell immediately if a magnet in a flywheel has reversed polarity but it is much more difficult to tell if a magnet is just weakened. For a flywheel to work the magnets must be different polarity, usually they are positioned North first followed by South but not always and some flywheels have more than two magnets to make things more complicated. That is why some saws need the polarity of those chip switches like the Megafire wired up differently if the South magnet is positioned as the first magnet to approach the coil.

Without a "Lot " of knowledge on electronics it sounds like the "swap out " may be the most straight forward approach . Work back to the flywheel from the more common components that you can test with a meeter . This is relatively unusual from what Im reading.

 

[Basher]

It is unusual to find reversed polarity and I have only seen two such incidents in 55 years of working on chainsaws and other small engines. I have fixed a few other chainsaws that we suspected had weak magnets but never really did any other test except swap on another spare flywheel that we had in stock and the engine ran like it should.

 

[jockeydeuce]

That's definitely a rare occurence!....Rare enough that I've never seen it...Good call on Dave's part!

 

[Marshy]

Now I can say I learned something today. AND I googled it and found out you can get a flywheel magnet charger for weak magnets. WHO KNEW? Mind blown.

 

[Mastermind]

I lost 6 full hours of my life chasing a 10 minute repair. lol

 

[idiotwithasaw]

I lost 6 full hours of my life chasing a 10 minute repair. lol

That's the story of my life. Blew an o ring on my planter literally a 5 minute job took 3 hours because I had neither the o ring or the tools with me to fix it. Made one trip to the shop gathered all the o rings I could find and grabbed some wrenches and went on my way. Git there and not only did I have the wrong size wrenches but it was so tight a wrench wouldn't work. I had to go back and get my set of 1" impact sockets metric and saw and an extension and strong arm. I can't remember what size I used but it was bigger than what comes in your standard socket set from sears.

 

[idiotwithasaw]

An even better one was a rebuilt injection pump on a 2150 Oliver tractor that took us 2 months to diagnose. Tractor wouldn't hit a lick, took it off retimed it no telling how many times. Took it back and had it checked once then the second time had the head rebuilt, had the injectors rebuilt too. Turns out who ever rebuilt it put the kill lever on upside down, we flipped it around and she fired right up pretty as you please. This is a pretty expensive play tractor at this point.

 

[Simondo]

That's the story of my life. Blew an o ring on my planter literally a 5 minute job took 3 hours because I had neither the o ring or the tools with me to fix it. Made one trip to the shop gathered all the o rings I could find and grabbed some wrenches and went on my way. Git there and not only did I have the wrong size wrenches but it was so tight a wrench wouldn't work. I had to go back and get my set of 1" impact sockets metric and saw and an extension and strong arm. I can't remember what size I used but it was bigger than what comes in your standard socket set from sears.

Dave ...Iv go to ask and hope you dont mind ... how did you come up with the fly wheel being at fault as its one of the most unusual things ?? a light bulb moment , divine intervention ........

 

[Fish]

Dave ...Iv go to ask and hope you dont mind ... how did you come up with the fly wheel being at fault as its one of the most unusual things ?? a light bulb moment , divine intervention ........

Ran out of options...

 

[Definitive Dave]

actually it happened to me before
I sent a builder a "box of saw" and when he was done he said the ignition was bad but everything else was good.
I checked it on other saws and it produced weak or no spark except some pretty decent spark with an old grimey Bosch plug.
When I studied it I realized the strange faded sharpy letters on the back actually said " bad magnet".
I must have gotten it in a bunch of parts somewhere and always thought it was odd that someone saved it but marked it as bad
weird stuff sticks with me

 

[hseII]

Yet you were conquered by an 064. Lol

And a Peanut

 

[VinceGU05]

Compression 200psi
Good spark
Flywheel key is good.

its low on compression.. mine has 240.