Restoration of a Bosch ZEV magneto

[BoschZEV]

While waiting for results of my capacitor tests, if you go to the following link you will find a new post I just uploaded diagnosing in detail the cause of the failure of an aftermarket slip ring:

http://www.britbike.com/forums/ubbth...338#Post507338

As I write there, although the results of that dissection and analysis apply only to that one specific slip ring, the implications for users of aftermarket electrical components are much broader. With most mechanical components on a motorcycle it's clear whether or not an aftermarket product works. Either the holes line up properly (or the bolt has the right pitch, or the fuel tank fits, or...), or they don't. There can be exceptions, like a badly heat-treated camshaft, but largely the average mechanic can tell when they install an aftermarket product whether it has the quality they expected.

Aftermarket electrical products are a different story, since they require specialized instruments to know whether claims about them are valid or not. This can be seen in the above post about slip rings. Without a particular highly specialized General Radio Megohm Bridge that measures to 1000 TOhm (a thousand, million, million ohms) I couldn't have made some of the measurements I made that were necessary to determine the cause of failure of that slip ring. As I say at the end of that post, the failure mode of this slip ring now has me investigating other ways for stress-testing slip rings that could be used by people who don't have the necessary specialized electrical test instruments.

[BoschZEV]

Unfortunately, the Panasonic condensers I tested so extensively for use in rotating armature magnetos are now out of production and no longer easily available:

http://www.britbike.com/forums/ubbth...734#Post467734

However, I have just completed a series of tests on an alternative that is currently in production and available at $2.70 for the pair needed for a magneto. As described in the link below, I did an accelerated lifetime test to the equivalent of 20+ years of storage at 72 oF plus 30,000 miles of use at a very high operating temperature. Details are at:

http://www.britbike.com/forums/ubbth...762#Post508762

Note that I have no financial stake whatever in these capacitors so I have nothing to gain whether or not you follow my recommendation. Also, it is worth emphasizing that the 20 years plus 30,000 miles is only a lower limit because, other than discoloration of the white plastic base, these capacitors showed no sign whatever of degradation when I ended the test after a month. There is no reason to expect they would not continue to last quite a bit longer.

[Tom Lovejoy]

Very interesting reading and as been said - thanks for your efforts and sharing this info. I am amazed any of our machines run. I have no idea what condition my mag's are in, however they have run dependable so far - knock on wood :-) Your site and the info on it are very good reading + appreciated by any and all who ride old vehicles with a magneto, thanks again.

[Tom Lovejoy]

One other thing this made me think about, doe's anyone have any experience with the new Magneto's being advertised in the AMCA mag?

[BoschZEV]

I am amazed any of our machines run. I have no idea what condition my mag's are in, however they have run dependable so far ...

Your experience is a testament to the fundamental reliability of these devices. However, some of them are nearly a century old so it shouldn't be surprising they need refurbishing. The unfortunate thing is that not everyone doing the refurbishing has been doing the reputation of these devices any favors.

[Slojo]

"I do what any rational person would do who has assembled a comprehensive set of instrumentation and facilities and actually knows how to diagnose and repair magnetos properly -- I repair them for free... "

BoschZEV

The last motor I built for a friend was so labor intensive due to engine case condition I could not justify charging him , it would have been to much.

joe

[BoschZEV]

The last motor I built for a friend was so labor intensive due to engine case condition I could not justify charging him , it would have been to much.

I understand this completely. Sometimes not charging anything for a very serious amount of work is the only reasonable thing to do.

[BoschZEV]

As I wrote a few days ago on the Parking Lot Chatter forum, for reasons I can't explain I recently spent just over $200 (+$14 shipping) to outbid 5 other guys for a totally trashed Bosch ZEV that looked like crap in the listing. Although the listing showed it to be missing the pickups and have the threaded end snapped off the armature, when I unpacked it I found it doesn't appear to be much worse than the one I dealt with in the following thread I wrote under the screen name 'Magnetoman':

http://www.britbike.com/forums/ubbth...733#Post446733




Although the photo doesn't show it, it is missing one of the two cam lobes as well as having the threaded end of the shaft broken off. However, overall it isn't all that much worse than the one I dealt with in the above thread. What this means is, if I ever do find a reason to restore this magneto it probably would take pretty much the same effort as the previous one, plus a full day to rewind the armature and vacuum impregnate it with the proper resin.

[BoschZEV]

Those of you with magnetos that have their condensers located adjacent to the points plate might be interested in a new Appendix to my Bosch ZEV restoration thread that I uploaded a few days ago:

http://www.britbike.com/forums/ubbth...361#Post540361

[10E]

BoschZEV
Off subject a little. On the last long ride, I rode through 3 hours of torrential rain, wind and everything he could throw at us. The ZEV mag never missed a beat.
No special protection was given to the mag. I'm wondering if I was lucky, or is there a potential in inclement weather for water to effect the mag.
If so, how would recommend going about protecting the mag.
Thank you for some very enlightening articles both on the this forum and the britbike forum.
Thank you in advance
1914 HD 10E

[BoschZEV]

is there a potential in inclement weather for water to effect the mag.
If so, how would recommend going about protecting the mag.

An important point is that water itself is an insulator so it would be possible for a magneto to run if totally submerged. Lucas made a magneto for trials competition called a "Wader" in their literature. The only actual concession the Wader made to water was the points housing was sealed, but with a tube in the cover to let the ozone out. However, the problem isn't the water, it's that most impurities in water act as a conductor. If those impurities end up in the wrong place the high voltage will use it to take a shortcut to ground.

The easiest place for water to enter a Bosch ZEV is in the points housing. However, there is no high voltage there so only if things are dirty inside the points housing and if the water carries electrically conductive "dirt" to the right place in the points will it cause a problem in this part of the circuit.

The high voltage pickups actually are sealed pretty well so it wouldn't be very easy for water to enter there. However, if it did it almost certainly would encounter carbon dust. Although that dust already was there it wasn't in the right place to cause problems (otherwise, your bike would have died before it even had rained), but if the water moves the carbon dust to someplace where it provides an easier path to ground the bike will stop.

I've certainly seen bikes give up in the rain because water got in the magneto. But, I've also seen a lot of bikes go through a lot of heavy rain without problem. So, to some extent you were lucky that your ZEV kept you going for as long as it did in heavy rain, but that it did isn't too surprising. The best thing you can do to prepare for the next torrential rain is to keep the internals as clean as possible.

[pete @ occhiolungo]

Hi 10E. When the new ZEV was introduced for the 1912/1913 bikes it was marketed as the new "waterproof" model. I'm not sure that the differences from the previous model with the open horseshoe magnet really effected more of a sealed unit, but that was the marketing claim.

regards,
Pete

PS, I've seen a few guys in the rainy UK smear bearing grease all over their magnetos, concentrating on the points cover edges and around the pickups. It seemed to help keep water out and minimize rust. Looked terrible though!

BoschZEV
Off subject a little. On the last long ride, I rode through 3 hours of torrential rain, wind and everything he could throw at us. The ZEV mag never missed a beat.
No special protection was given to the mag. I'm wondering if I was lucky, or is there a potential in inclement weather for water to effect the mag.
If so, how would recommend going about protecting the mag.
Thank you for some very enlightening articles both on the this forum and the britbike forum.
Thank you in advance
1914 HD 10E

[10E]

BoschZEV and Hi Pete.
Thanks for the information. Both of your suggestions sound good. "Clean inside, Greasy outside. --- not exactly sure about the Brit solution, sounds very British, but if helps and doesn't have side effects -- I'd go for it. Where do you get the British grease Pete :-)
ZEV, I'm very poor in regards electrics but your suggestions make an awful lot of sense, I hope it helps other people too.
I was trying to fly under the radar but you let the "cat out of the bag" Pete.
It's Cannonball time and I'm figuring we are going to run into some serious rain at some point. It may become an issue though I believe their will be few mags. on this run---mostly generators and batteries.
Thank you again
10E victor

[pete @ occhiolungo]

oops. I thought we all knew who 10E was! I've edited my note if you want to try to remain under that radar...

[BoschZEV]

The 2014 Cannonball is over and the Bosch ZEV magneto whose restoration I described in detail on another site* performed flawlessly for the 3000+ miles without having had any maintenance since I originally restored it for use in the 2012 Cannonball.

* http://www.britbike.com/forums/ubbth...733#Post446733

Bill Wood happened to mention at least four failed magnetos in his daily posts about this year's Cannonball. Although there certainly could have been others as well, given that most bikes this year did not have magnetos, even four is a very high percentage of failures. However, between the bench tester and actual road miles my friend's magneto has traveled over 5000 miles so far, which is consistent with my contention that there is no excuse for a properly rebuilt magneto to fail. And yet, rebuilt ones continue to fail with remarkable regularity...

Reliable Magnetos for the Next Cannonball

Word on the street is that the cutoff for the next Cannonball will be bikes at least 100-years old (pre-1916) so having a reliable magneto will be essential for the success or failure of most of those machines. This has seeded an idea, although one that clearly has flaws.

While I don't have any interest whatever in rebuilding magnetos as a business, how about doing so in trade for enough parts and components for me to piece together my own pre-'16 Frankenbike to ride in the next Cannonball? This also would be an interesting project to document in a series of magazine articles. Rather than cash changing hands, the idea, ill-conceived as it is, would be to completely restore to the highest electrical and mechanical standard some ten or so magnetos in exchange for appropriate piles of motorcycle parts gathering dust in the back of barns. If you think in terms of $500 to restore a magneto this idea clearly makes no sense. However, if you think ~10x that for the level of instrumentation, facilities and time that would be applied as shown in the above link, and for the quality and reliability that would be the result, it isn't ureasonable (as if anything we do with old motorcycles is "reasonable"...).

The next Cannonball is two years away, but time will pass quickly. Given my other obligations, completely rebuilding ten magnetos to a proper high standard couldn't happen overnight (nor could building a reliable motorcycle out of piles of mismatched parts). So, if people are happy to start out on the next cross-country ride with the magnetos they already have, or with magneto rebuilders they've used in the past, and/or if no one stumbles across this thread and takes me up on this idea in the next few months (or proposes something better), time will have run out.