Joined: Apr 2009
Location: STL, MO, USA
Ridingagin, All the cooked ones I saw with my own eyes had fully cocked, so I couldn't determine the primary failure point with my eyes.
That said, it never has looked like a very quality stator. I say this with a grain of salt cause I'm educated in car alternators and industrial motors, not motorcycle stators.
This however is my observation. The finish on the core is thin epoxy looking stuff with pretty sharp edges. There are no sleeves or insulators of any kind protecting the magnet wire from grounding on the core other then the thin epoxy like finish.
Steveman, I wouldn't rule out ambient temperatures inside the case or of the case itself, nor oil cooling or the lack there of. The magnet wire itself generates a lot of heat. That heat leaves by convection, conduction, and radiation. The warmer the case, oil, and gases are, even though still bellow the maximum temperature the magnet wire insulation can take, the slower the magnet wire can shed heat through the above named dynamics.
Also, for the types of insulation above, whats listed is the maximum RATED temperature. They SHOULD hold up to the maximum rated temperature for a considerable while, but not forever and NOT if they have any flaws or were at all damaged during the winding process. Its a non linear slope, how long they will take whatever temperature.
In any case, winding a stator is always a flawed procedure that works because of "defense in depth" I'm sure the magnet wire is dipped more then once in the hopes that flaws won't line up and so its more resistant to abrasions, cracks, bubbles, and what have you. The core is epoxied and though not here, usually the channels are tubed or spaced to prevent grounds here.
What I'm saying is it's not a matter of doing it right or wrong. It's never perfect and is rarely terrible, and every little thing helps to make the stator last longer.
I don't know if these stators are dying from heat, voltage spikes, movement, solvent damage, heat shock, poor winding, overload, or what.
Either way, it's no different then the guy that smokes like a chimney, drinks like a fish, stresses day in and day out and enjoys blow every weekend. Perhaps he will die of cancer, or maybe his cause of death will be a heart attack, but the real underlying causes were all of the above with age and heredity kicked in.
No matter the ultimate cause of stator failure, improving any of the things that age stators will increase it's life. No stator lives forever, they will all die, we just want to make them live longer.
Owned to date. Honda Aero 50, Honda Elite 80, Honda Elite 250x2, Suzuki Katana, Suzuki RF600, Yamaha YZF1000R, Kymco Xciting 500, Suzuki GS500, Suzuki Burgman 650, BMW F800GSx2, BMW S1000RR, Aprilia Scarabeo 200, Aprilia Caponord, Aprilia Sportcity 250
I love and miss you Jeneca and I'm sorry.