crappy chinese components(specifically magneto)

[rogersverobeach1]

I've asked if anyone knows of some afermarket magneto's but no reply.
This bike will be the death of me.i've had a Grubee for about 3 months.
I put alot of miles on it,but already gone through four mags,two clutch cables,carb cables, and two carbs.

I NEED A MAGNETO THAT WILL LAST LONGER THAN ONE DAY TO A WEEK.
This is obviosly a flaw in the engineering.It burns in the same place every time.Anybody with a little common sense and some knowledge of electricity and mathematics can tell you if you have a coil of wire(magneto)and electricity is traveling through it,when it comes to two 90o turns there is going to be a great amount of resistance and heat therefore burning the cheap crapp wire being used.this is at the last lenghth of wire where it is grounded to core.I'm tired of having to resolder this thing.the latest mag lasted maybe two miles.the third lasted a couple hundred.
ANY SUGGESTIONS?

 

[arceeguy]

While I haven't seen a huge percentage of magneto failures, it does seem to be a weak spot - along with the CDI/Coil module.

The only "real" cure is having a motor rebuilding shop rewind the magneto. It seems that many of the components used in HT engines are sourced from the same manufacturer and just assembled by different "manufacturers".

 

[Fabian]

It's surprising how much variation there is between manufacturers of these engines.

I've had a hellish time with connecting rod bearing failures, yet others have no such issues.
In my case the electrical system has been the most reliable part of the engine assembly with 4,500 kilometers (2800 miles) on the original magneto and CDI.
Yes i've replaced engines but swapped over the original electrics to test their longevity.

Fabian

 

[AussieSteve]

Electrics/electronics is my favourite subject and was my profession for 20 years, so I'll add my 2c worth here. (Try and stop me!)

After seeing how much $@#&*% I just wrote below, better make that $2 worth.

1. A bend in a wire will not increase it's resistance. (If you doubt that, grab a low-ohms meter and measure a wire, then bend it and test again.) There will be no difference.

2. Rewinding won't really help. To fit the maggy in the available space and supply the same voltage and current, it will need to be wound with the same gauge wire, with the same number of turns, to use the original core. The result will be the same coil. (I have a coil-winding machine and the knowledge, but wouldn't waste my time.)

3. It is not typical to go through so many magnetos. Something else appears to be wrong. (4 in 3 months is horrendous.)

4. You'd find that the cheap crapp wire is exactly the same as that used by most manufacturers. It will be copper wire, coated in enamel or polyurethane, with a very precise diameter to allow it to be used on coil-winding machines. They're programmable for very precise wire thicknesses or they wouldn't work. Even my home-made one is adjustable to within 18 micrometres. (18/1000mm)
What causes the failure is an overload. The spot where the wire fails is inevitably the same in most cases. Where the wire leaves the main coil, but before the solder blob, the wire can no longer sink excess heat into the main mass of the coil, so it becomes the weak link and often goes open-circuit with excessive loading. I've read a lot on this subject on this site and it all fits.

Do you have anything connected to the white (kill-switch) wire besides a kill-switch?
How is your kill-switch connected? (white to ground or blue to ground.)
If you're not using your white wire for anything, is it well insulated so that it can't touch electrical ground anywhere? Also, even a partial short between blue and white could cause magnetos to fail, so check your wiring carefully.

Almost forgot - the other thing to look at is your waterproofing. It's possible that moisture is getting into the magneto.
Silicon where the wires come out of the casing helps.
Also, it's not a bad idea to use sealant on the magneto cover.

Sometimes too much emphasis is placed on the components instead of the nut behind the wheel. Not calling you a nut - just thought it sounded good. I'm going through a second childhood, I think.

... Steve

 

[Fabian]

Funny about that Steve - prior to reading your post, it seems i've followed your exact instructions:

the other thing to look at is your waterproofing. It's possible that moisture is getting into the magneto.
Silicon where the wires come out of the casing helps.
Also, it's not a bad idea to use sealant on the magneto cover.

 

[Fabian]

I've also slapped silicone sealant onto the black and blue wires where they enter the CDI, furthermore slapping silicon sealant around the outside of the sparkplug wire where it screws into the CDI.

Fabian

 

[AussieSteve]

Yep, I put silicon around the HT lead junction on my CDI too. That's probably even more important than the black and blue wires, due to the higher voltage, (between 5,000V and 15,000V) and the chance of arcing with dust and moisture.
Despite all the hype for fancy leads and caps, I'm still using the stock copper lead and cap and there are no problems. Nor should there be. We don't need low-noise carbon leads or other stuff. Nothing conducts better than copper, for our purpose and if you keep the lead and cap free of dust build-up, you shouldn't have any trouble.
N.B. If you fit a radio or television to your bike, you might want to consider the low-noise option.

With your mileage, I'll assume that you've adopted the recommended wiring. ie white to kill switch (only), blue to CDI. Definitely no kill-switch on blue.

... Steve

 

[Fabian]

Yes, white wire goes to kill switch, and it makes sense as from what i understand, the white wire is low voltage, preventing high voltage arcing across the kill wire switch.

Strange thing is, i was advised by another vendor that the correct method is to splice the kill switch into the blue wire and run it to ground.

Fabian

 

[AussieSteve]

Yeah, mate, I've read that advice too, but don't follow it. There's a very good reason why your magnetos don't fail. You wire everything correctly.
It's not merely a voltage issue. You'd probably measure similar voltages on both the blue and white wires, open-circuit, in the neighbourhood of 6-12V probably. Under load, though, such as a short-circuit from a kill-switch, the white wire winding would have a higher series resistance due to thinner wire and probably looser coupling to the core, so that not much current flows under that short-circuit condition.
The blue wire is attached to a coil with a higher current potential, (thicker wire and better magnetic coupling) and can't handle a short in the same way.

I've been thinking about another electrical issue - running a small dynamo/generator from the jackshaft to charge a small 6V/12V 5-7Ah SLA battery for lights etc.
I'll let you know if I come up with anything decent. It's weeks away, but who knows?
It would only be useable with a SBP shift kit jackshaft, though, because anything else would be too hard to implement. If I do come up with anything decent, I probably should have a chat to Paul and Jim at SBP.

... Steve

 

[wildemere]

Bending a conducter changes resistance, thats how loadcells and other transducers work. Not much of a change in R or revelance to the HT coil issue though.