Mighty Mite odd starting behaviour after damage

[RRRocketMan]

Remington Mighty Mite 34cc

So here's the summary of what happened:

1) I was out back sawing wood when the chain got stuck and instantly stalled out the saw... like instantly. I pulled it out and noticed a rattle coming from the recoil assembly.
2) Like a moron I ignored the sound and started the saw again. Immediately I heard even more rattling that went away after starting so I finished my cuts and then examined the recoil area. There were metal pieces inside.
3) Moron again tries to start the saw but this time there's no bite and the chord just goes back and forth freely.
4) I disassemble the recoil and find several flywheel teeth broken, the starter cup almost completely exploded and the springloaded starting pawls exploded too.

A few days later

5) I purchase a replacement starter cup and entire recoil assembly, from which I remove the stamping that holds the pawls and spring. I transfer this and the starter cup over to the damaged saw and complete repairs. Now the saw recoils even better than it did before... only now I'm missing some flywheel teeth, which I figure is no big deal.
6) I attempt to start the saw and after a few pulls it starts but the chord won't retract. I shut the saw off and it retracts.
7) I try to start the saw again and the chord rips from my hand. I try again, same thing. As soon as the magneto produces a spark, the recoil seems to go backwards and rip the chord from my hand.
8) At this point I'm worried I'm going to break something again so I stop trying to start the saw.

Conclusion: The recoil assembly has been properly repaired and works quite well but something has changed that I'm not aware of and now the saw wants to break itself every time I start it. What it feels like is the cylinder firing in reverse, because the chord retracts out of my hand as soon as the plug fires... but I can't confirm which way it was rotating. I would also "theorize" that somehow the saw is destroying the recoil assembly because the recoil assembly either isn't letting go of the starter cup or the starter cup is catching the pawls after having started.

Does any of this sound familiar to anyone and what the heck could it be???

Thanks.

 

[atpchas]

Check the flywheel key. If it is sheared and the fw has slipped on the crankshaft, the saw could well be firing early and producing the effects you describe.

 

[RRRocketMan]

Doesn't look sheared to me. Is the timing based on where the magnet is embedded in the flywheel itself or is there some other mechanism for timing? If the flywheel hasn't moved, could timing have been affected?

 

[SteveSr]

Doesn't look sheared to me. Is the timing based on where the magnet is embedded in the flywheel itself or is there some other mechanism for timing? If the flywheel hasn't moved, could timing have been affected?

Is this a points ignition or electronic?

Electronic could possibly fail with a timing issue. The only way to confirm would be to substitute another known good coil.

While you are at it measure the secondary coil resistance from the spark plug connector to ground (cylinder). Also are you using the specified resistor or non-resistor plug?

 

[RRRocketMan]

It's points and the spark plug and wiring is all original and the same as prior to the symptoms. What is the normal timing on these things anyway? I only know cars but in a car, there are so many provisions to prevent knock and with multiple cylinders, if 1 tries to go backwards it's simply impossible. With single cyl small engines like these I would think the timing would have to be fairly retarded in order to prevent any possible issue. Maybe leaning out the mixture would help? I once determined that 12.2:1 was the fastest combustion mixture for cars and I assume it would apply to all gas engines.

 

[SteveSr]

It's points and the spark plug and wiring is all original and the same as prior to the symptoms. What is the normal timing on these things anyway? I only know cars but in a car, there are so many provisions to prevent knock and with multiple cylinders, if 1 tries to go backwards it's simply impossible. With single cyl small engines like these I would think the timing would have to be fairly retarded in order to prevent any possible issue. Maybe leaning out the mixture would help? I once determined that 12.2:1 was the fastest combustion mixture for cars and I assume it would apply to all gas engines.

With points it is easy to check timing. The spark occurs immediately when the points open. You can check this with a simple continuity tester. Mark TDC and then mark where the points open. Get out a protractor or a degree wheel and measure. Compare your measurement to the engine specification.

 

[RRRocketMan]

The math is not a problem but you lost me on the physical procedure. If I have the recoil cover off, there's not much I can access. Is this something I have to take the flywheel off to do? If not, what am I checking continuity of exactly? Sorry, I just don't know the anatomy of chainsaws well enough to just "get it"

 

[SteveSr]

The math is not a problem but you lost me on the physical procedure. If I have the recoil cover off, there's not much I can access. Is this something I have to take the flywheel off to do? If not, what am I checking continuity of exactly? Sorry, I just don't know the anatomy of chainsaws well enough to just "get it"

There should be a wire comming out from under the flywheel that goes to the points. The other end of this wire goes to the coil. Hopefully there is a quick dosconnect of this wire on the coil which will make testing easier. Some photos would definitely help.

 

[pioneerguy600]

Pull the flywheel off the crank, inspect the key is still good, ,if the flywheel has slipped even a few degrees it could fire backwards. Normally a chainsaw engine fires about 20 degrees before TDC and some electronic module saws have a retard function built into the module. Check to see where the magnets in the flywheel are located when the piston is at TDC, it should be slightly below the coil center.