bad rotor after all these years

crassius

crassius

Well-Known Member
finally found a bad rotor on a motor that sat for 5 or 6 years - replaced rotor and all was well

motor ran before sitting all those years so sitting may be a cause of that weakness over time
 
We're talking 'magnet', right? I call it a 'rotor' too but not sure everyone else does.

The magnet is the rotor, the magneto coil/frame is the 'stator'. At least if you use proper terminology.

Easy way to remember between the two. The 'rotor' rotates. The 'stator' stays where it is.

Tom
 
yeah, it got so weak that it wouldn't stick to my toolbox on one side

got a lot of them around here, so may start storing them as a circular daisy chain to keep them all fresh

somewhere packed away I have a magentizer to restore magnets in 1950s BHT magnetos, but not wanting to dig it out
 
What would symptoms be for a bad rotor? Weak little spark? Hard Start? I got a bike that simply falls all over itself at the top end. Could a weak rotor do that? Got an NT on it. Tweaked and fussed and messed with it all last year. I run a pocket bike exp chamber exhaust, I stuffed a male battery terminal cleaner into the end for positive back pressure. It Does run better under a load but still seems to fall flat when I wind it up on level ground. Hmm.. Food for thought. Thanks Crassius.
 
a weak rotor has a weak spark at low speeds - expansion chambers can make more power, but it happens only at certain speeds - the reflected wave always takes same time to reach cylinder, so only scavenges at the RPM that has that amount of time between firings
 
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