Chainsaw flywheel switching polarity of magnets?

[Fuzy6525]

Saw a video last night of someone “referencing “ another video about someone removing a flywheel the tooless way, hammering it off with a hammer and punch. Said it somehow reversed the polarity of the magnets.
Can this actually happen? Believe this was a saw that had points if that makes a difference. Thanks

 

[Backstage]

That would be very surprising. The “tool-less” removal with a hammer is just to wobble it off the taper with a plastic deadblow or wood mallet.

 

[dynodave]

For points, magnet polarity does not matter. For the simpler type EI it typically does. The shape of the magnet and how it is attached and lays against the the "armature" could be the entire key as to if it would work or not. Share the link for the video and I'll give it a peak...

 

[pioneerguy600]

If the magnet itself is hit hard it can. It happened on one saw of ours. My dads 116 SD, The module vibrated loose on his new saw, only 47 days old and the magnet struck the module mushrooming it really badly. The dealer replaced the module but could not get the saw to fire again, after much head scratching I took out my hunting compass. Both magnets now had the same polarity so we swapped on a replacement flywheel and the saw fired off immediately.

 

[Fuzy6525]

That would be very surprising. The “tool-less” removal with a hammer is just to wobble it off the taper with a plastic deadblow or wood mallet.

Thanks for that. Never heard of it either.

 

[Fuzy6525]

For points, magnet polarity does not matter. For the simpler type EI it typically does. The shape of the magnet and how it is attached and lays against the the "armature" could be the entire key as to if it would work or not. Share the link for the video and I'll give it a peak...

Thanks for the info. Doubt I could find the link. The guy said he had seen or heard it but don’t think he said where. It was on YouTube of course.

 

[Fuzy6525]

If the magnet itself is hit hard it can. It happened on one saw of ours. My dads 116 SD, The module vibrated loose on his new saw, only 47 days old and the magnet struck the module mushrooming it really badly. The dealer replaced the module but could not get the saw to fire again, after much head scratching I took out my hunting compass. Both magnets now had the same polarity so we swapped on a replacement flywheel and the saw fired off immediately.

Guess you could also check with another magnet? One would stick and the other repel? Or might that damage the way the current draws?

 

[pioneerguy600]

Guess you could also check with another magnet? One would stick and the other repel? Or might that damage the way the current draws?

A magnet would work, I have used a pencil type several times checking flywheels, no damage to them. I used a compass as it was in my hunting jacket pocket at the time we were working on the 116.

 

[Bob Hedgecutter]

Not sure it was reversed polarity- as much as damaged or shattered magnets- but I have seen a flywheel dropped on a concrete workshop floor (by a Stihl Tech in a Stihl shop) and after the sudden stop at the end of the fall, the flywheel was useless for its intended purpose and it cost the shop a new flywheel to get the saw (MS 660) going again.

 

[HarleyT]

flywheel dropped on a concrete workshop floor (by a Stihl Tech in a Stihl shop)

They have an advanced class for this.......

 

[Bob Hedgecutter]

They have an advanced class for this.......

If I did deep enough through the screeds of paper I have here headed with STIHL, I am bound to find the service manual bulletin, giving step by step proper operating procedures to complete the task!

 

[Maintenance supervisor]

Once I started my 090(clone) after porting and rebuild and the SOB ran backwards!
It happens when you dont pull the cord fast enough sometimes. This is probably the confusion of the polarization reversing.

 

[av8or3]

I think it possible that magnets BREAK. When that happens you now have multiple fields instead of the one intended. Magneto won’t work with broken magnets.

 

[Okie]

Kinda doubtful that a flywheels magnet would completely reverse polarity by using the whack method for flywheel removal unless maybe the magnet cracked or broke .I also keep a heads up and remain skeptical when viewing you tube stuff.
BUT:

I've seen some of the EZ model homelites that the Flywheel polarity has to be correct for BOTH the points ign and the electronic ign. Electrtonic ign has a reversed polarity flywheel magnet as compared to the points flywheel when used on the EZ's AND Homelite even reversed the polarity of some of their flywheels due to a supply shortage of one brand so as the EZ production would not be halted.. Using a battery powered reverse able drill and spinning the flywheel backwards with the spark plug removed on a points ign flywheel would produce a weaker spark and no spark at all on the electronic ign.
I could easily determine (compare) the polarity of the different flywheels (Phelon vs Wico/Prestolite) magnets by sticking a small screwdriver to the magnet and use a compass. (using the screwdriver as a magnetic antenna)
Could do this while the flywheel was still installed on the saw. (Did not have to remove the flywheel to determine the magnets polarity)

 

[dynodave]

Here the load material is embedded in the cast aluminum. After all the flywheel machining, the load is magnetized. I have a magnet gausser and have magnetized enough magneto to have a clue! There are many different flywheel magnet configurations, so discussing them according to points/EI can become significantly more involved than talking at the bar...For example as I have mentioned here before, early horizontal shaft cast iron briggs and straton MUST be polarity reversed to change from original points to later OEM type EI.
Where the load material is external and riveted in place , the physical switch could possibly be done.
Poulan 3400 flywheel +north on left and on right south - The focusing armature steel is what you see externally not the magnet

 

[cscltd]

Maybe reversing polarity is not the correct word or what is really happenin, but we call to make it simple?
the impact could disrupt the effectiveness or something of one of the magnets even though it may still feel like it has magnetism?
I do see the odd one, but very rare, had a 288xp many many years ago that did this, and it helped that another was in around to do a swapnostics.
Some of the plastic/metal Stihl flywheels ones can fool you as the plastic spins on key. Doing the old way of checking top deep centre to magnets can usually rule that issue out.

 

[grön ek]

Saw a video last night of someone “referencing “ another video about someone removing a flywheel the tooless way, hammering it off with a hammer and punch. Said it somehow reversed the polarity of the magnets.
Can this actually happen? Believe this was a saw that had points if that makes a difference. Thanks

it will not reverse the magnets polarity, that is total BS, I've done it for years without special tools, and although I never checked the polarity, EVERY machine ran fine

 

[KASH]

On the Briggs mount the coil upside down.
Kash

 

[Old2stroke]

Here the load material is embedded in the cast aluminum. After all the flywheel machining, the load is magnetized. I have a magnet gausser and have magnetized enough magneto to have a clue! There are many different flywheel magnet configurations, so discussing them according to points/EI can become significantly more involved than talking at the bar...For example as I have mentioned here before, early horizontal shaft cast iron briggs and straton MUST be polarity reversed to change from original points to later OEM type EI.
Where the load material is external and riveted in place , the physical switch could possibly be done.
Poulan 3400 flywheel +north on left and on right south - The focusing armature steel is what you see externally not the magnet View attachment 953336

Great photo. So many people think there are two separate magnets or just one huge funny shaped one.

 

[Fuzy6525]

They have an advanced class for this.......

Now that’s funny, I don’t care who you are!