Can Stators get heat affected?

Greetings Gents,

Last month i took my 1999 FE501 to the Cape. The old girl and i did not make it to the top however...we stopped 50Kms from the tip which was a total bugger!

The scenario........

The bike was running well for most of the trip however had been becoming increasingly difficult to start when hot on the kicker and pretty much impossible to start on the electric when hot.

We had been blazing up a development road holding things flat out for and 1.5hrs and was coming into our fuel stop when it was like the hand of god reached down from the clouds and turned the ignition off! All spark just dropped out and everything came to a groaning halt. We checked all the obvious stuff like ignition lead, plug cap and electrical loom and connectors. Everything seemed good and buy the time we decided to kick it over about 0.5hrs had lapsed. After about 2 mins of kicking she fired up and we took off for another 15min blaze through the dust before the ignition cut out again.

We were running out of time by this stage to beat sunset and make it across the Jardine River barge so we put her in the support truck and headed for camp. The next day I found the following.

1.0 That night I noted that the spark is week (compared to the giant blue arch that leaped out form my mates KTM 525 Lead to his engine casing)
2.0 The next morning I found a magnet had come out of the array (I glued this back in place with high heat araldite and the poles are correct)
3.0 After the glue had set I fired it up and drove it without problem for about 40mins. Just when I turned it back towards camp thinking that I had fixed the problem and that I was good fro the return trip back to Cairns it completely cut out on me. Three times now this has happened on completely different terrain and driving scenarios.

The only thing that seems like a reliable factor is that the ignition fails when it is hot and comes back again when it is cold.

I am yet to check my cold and hot stator resistance level. I will do that tomorrow.

The thing I find amazing is that I have never heard of any electrical components, especially stators being so affected by heat…I would have thought that they would completely let go and not half arse operate when cold?

Any thoughts or similar experiences and solutions would be greatly appreciated .

Davo.

hello, what is most propably happening is due to vibrations and not to heat.
inside your stator is the ignition coil (3kohms resistance in your case between red-black) that is either in a short circuit condition or an opened circuit condition. with the vibrations the wires that cause the short circuit may move and not cause a problem untill they move again!! same thing with the open circuit assumption, the 2 leads come together temporarilly and you have a spark!

you can hit gently on to the ignition coil which is located at 6 o clock on to the stator and some times you get a temporary but pricelles fix until you go home or wherever..

Hi Davo,

What you have here is deterioration of the enamel on the windings, this a very common occurrence on some of the Jap ignition stators due to the poor quality of the copper enameled wire.

When heat is applied to any electrical device it insulation properties fall and this is what happens to the SEM stator, with it getting heated up and then cooled numerous times the enamel gets fatigued and you end up with shorted turns on the output source coils when the engine gets hot and the spark fails hence when the engine cools the spark returns, the time duration will get shorter and shorter.

The enameled wire I use is of a very high quality and will withstand 200 C twice the normal running temp of the engine.
If you want your stator rewinding just send me a PM.

Regards

Sparks.

RE: Re: Can Stators get heat affected?

lineaweaver has always claimed that it was heat related. sparks should know and syas that it's poor insulation.

for me, as the user, i drill a hole under the case and that's about all you can do!

regards

Taffy

Re: RE: Re: Can Stators get heat affected?

That story sounds so similar to what happened to me on a TE Husky with the same SEM ignition on a trip to Birdsville. It got so that it would only start by towing it behind another bike, spinning the engine really fast and then you had to keep it revving hard or it would stop. I rewound the stator CDI charging coils, but not the trigger coil and it fixed it completely.

I have also had the same problem with an old DR250S. It would start & run fine when cold & stop when it warmed up. In this case it was the trigger coil that was crook. You could dip it in hot then cold water & it would coneect & go open circuit like a temperature switch. Once rewound it worked fine. The CDI charging and trigger coils are separate on those old jobs.

Taffy said:

lineaweaver has always claimed that it was heat related.

Click to expand...

Sorry to disagree Taff, but I remember Dale posting about the BBR501 experiment he worked on. He claimed that the unbalanced non e-start 501 engine in the custom twin loop frame acted like a big tuning fork and the vibration destroyed stators mercilessly.

Re: RE: Re: Can Stators get heat affected?

we'll see how he fairs with my rewound ones, i did a couple for him earlier this year for some sort of project he was doing.

regards

sparks.

RE: Re: RE: Re: Can Stators get heat affected?

brad

you make my point for me. in that frame!!

either way i'm not fussed.

regards

Taffy

Re: RE: Re: RE: Re: Can Stators get heat affected?

Taffy said:

you make my point for me. in that frame!!

Click to expand...

Zactly sir!

One thing that doesn't seem to be mentioned in the stator failure debate & I reckon might be a major cause of CDI charging coil failures:

The flywheel magnets are travelling north then south past the poles of the stator at about 500Hz but the frequency chances with engine speed.

This induces a current in the stator windings - the whole point of the stator in the first place!

This current creates its own magnetic field which reacts against those from the magnets, generating an oscillating force from within the wires themselves. What this does is induce a 500Hz oscillation between the winding wires if they are not locked solidly to each other en masse.

The movement both wears the insulation on the winding wire allowing turns to short together and /or work hardens the copper wire until it fractures and the coil goes open-circuit. Note these wires, including insulation aren't much thicker than your hair! Significant 500Hz oscillation is easily possible due to the tiny mass of the wire.

Also this oscillation is completely independent to any shaking the stator may be doing as a whole due to it being bolted directly to an engine block and is at a much higher frequency.

It appears to me the the stator coils are wound dry. I believe they should be coated in lacquer or similar (so long as it doesn't soften the insulation) as they are wound to lock the wires solidly togeter . I used nail polish & it seemed to work well.

Re: RE: Re: RE: Re: Can Stators get heat affected?

Brad, most of your electrical theory is correct but like most topics that come up on this site people look into to them to deeply they can-t see the woods for the trees and get grossly lost in the topic they are talking about.
What some peoples postings only require a simple answer end up being quoted quantum physics.

Regarding the SEM windings they don't burn out they are not wound dry, the problem like i have said many times before is the bucking enameled wire the factory use is the lowest grade you can get.

When you buy copper winding wire the biggest cost is quality of the enamel and if you use a lot like SEM do then this will have big bearing on your profits plus if the units don't last long they will have to sell more, I think they call it making money.

If it was anything out side the quality of the enameled wire then surly I would get failures to up to press not seen one back.

Regards

Sparks.