So what kills stators?

[Guest]

I know I was asking around in my other thread, but this is a different subject. I've been trying to figure out where I want to go in fixing this. I've been reading up on endless amounts of stator and r/r threads but my example seems more extreme then the rest where it's mechanical neglect.


What I want to know is what can cause a new stator that looks like this


and make it look like this in under 1,000 miles?




The oil level is correct because I check it before every ride, my connections are good and clean, the R/R diodes (honda shindingen unit) check out and I dont have any power surges when riding, the grounds are good, fuse box has been cleaned in vinegar. The bike isn't running super lean and overheating...

Since I put in the stator I've ridden it around town a few times but mostly longer trips and my commute to work (around 65 miles @ 7000rpm for an hour and a half at a time, each way). I read up on here that the stator is being stressed more at high RPM, but could a few trips to work and sunday rides kill a new stator this fast? I've seen pics on here of people's old stators and they look nothing like this...

Is it just a faulty stator? Something I noticed between this one and the old one, is that the copper wires that come from the stator and go into the insulated wires going to the R/R had gotten so hot they were basically fried off. On the old one it wasn't even attached but the new one had one that was detached, one solid and the other loose and came off when examining it after removing.

[Nessism]

Did you wire the stator into the regular factory harness or did you wire it directly into the R/R? The regular harness forces the current along a convoluted path with needless connectors, that often corrode and add unnecessary resistance.

[Toasty]

Yep, it's wired directly to the R/R. The r/r is grounded to the battery and the sense wire is hooked up and all good too.

[posplayr]

Lsd.........

[posplayr]

Lsd......... ......

[SqDancerLynn1]

In the stator pages ? did you check the B+ battery to the fuse block B+...

[tkent02]

I have never seen it except for bikes with poor connections. My first GS 550 was rarely run under 7,000 RPM, it's stator lasted 150,000 or so miles at least, still going strong last I heard.

[BassCliff]

Hi,

Let me ponder on my keyboard for a bit....

For some reason that stator is running way to hot. Could be too much resistance in the charging system in the connectors, grounds, fuse box, etc. Could be an inferior design in the r/r unit passing too much current back to the stator instead of shunting it to ground and heating the r/r itself. What regulator/rectifier unit are you using? Are you using a single point frame ground? What is the voltage loss between the r/r output and the positive battery terminal?

Thank you for your indulgence,

BassCliff

[Mekanix]

Is something missing here?

I don't see any epoxy on the coils. Heat and vibration could have eroded the thin resin coating on the wire and shorted itself out one piece at a time.

[posplayr]

Is something missing here?

I don't see any epoxy on the coils. Heat and vibration could have eroded the thin resin coating on the wire and shorted itself out one piece at a time.

Yep that is a real thin coat of epoxy


So everybody else knows:

as the rotor magnets move around the stator there are magnetic forces applied to each of the stator windings causing the wire to move and flex. After a while the wire will work harden and break or just wear through the small amount of insulation it has and short out. That is why the stator windings need to be embedded in a hard epoxy that prevents movement of the wires.

That I why I like the Electrosport stators; they have a nice coating of epoxy powerdercoat

[tom203]

Toasty laments.....

"What I want to know is what can cause a new stator that looks like this"

Even with decent connections, the stator gets real hot. An inferior grade of magnet wire (think cheap) will degrade and short out on itself and then really heat up. Blue goop holds windings in place nicely , but also holds generated heat in (and covers sloppy winding). I found an article about a ES stator problem on a Honda cx-500- won't link here, but the guy went thru two Electrosports stators due to bad winding technique. Personally, I prefer a light clear epoxy coating.

[tom203]

Here's a pic of cooked ES stator off honda- this happenned when one of phases shorted to ground . other pics in link

http://www.genebitsystems.com/david/MotorcyclePrep/statorfailure.htm

[duaneage]

Hot oil has quite a bit to do with stator demise. Air cooled stators on other machines don't suffer from this problem nearly as much.
A shorted diode in the rectifier section of the regulator is as likely to damage a stator. Even if the stator survives a bad regulator, it is damaged enough where eventually it will fail.

[koolaid_kid]

An interesting observation. My air-cooled GPz stator looks pristine, and the system charges extremely well.
It reminds me of automatic transmission coolers that are part of the radiator. The radiator actually heats up the transmission fluid most of the time, rather than cooling it down.
So if your bike's oil temp is around 300 degrees like my GS was, prior to an oil cooler installation, you are actually taking the temp up to 300 degrees.

[duaneage]

Honda CM and CB 400 bikes rarely have stator problems and never have RR failures. I've seen some of the WORST connections on the terminals of the RRs. No one is keeping them pristine and corrosion free yet the RRs don't break and the stators stay alive.
I always chuckle about the need to keep the connections perfect to prevent the RR from failing. Clean connections are very important for a lot of reasons but have nothing to do with RR failures. One Honda RR suffered from the copper wire turning green on all the leads back to the case, I was amazed it still worked but pitched it anyway.

Crappy diodes in OEM regulators are to blame for most of the RR problems.