My Bosch Rotor Needs to Magnitized?

[Semper Gumby]

OK - so I'm having a bit of trouble with my new Euromotoelectric ignition (my fault) and I'm on their website when I see this.

"Permanently Magnetizing your Bosch Alternator Rotor." and the link takes me here -

https://www.euromotoelectrics.com/v/vspfiles/assets/images/permanently%20magnetizing%20your%20bosch%20alternator%20rotor.pdf

Hell yes I have suffered with this problem.  Has anybody else had this?

My symptoms are first start of the day the GEN light stays on till about 3000 rpms then after that it stays on till about 2500 rpms.

[Bob_Roller]

I havn't, I posted that link about 3 months ago and it seems like no one else had heard of it either .
I even posted it on a Guzzi forum, the older bikes have the same Bosch charging system as the airheads and no one there had ever heard of it either .

[Semper Gumby]

Well I hunted down and killed the right power supply.  It will be here in a few days.

I'll keep you posted.  After all this time....could it really be a simple as this :-?

http://www.vetco.net/catalog/product_info.php?products_id=14092&osCsid=buljob0hote1lliomneacoj963

[Barry]

I see what they are suggesting for permanently magnetising the rotor just don't see why it should be necessary or why the Gen lamp should stay on  above idle.

"When running your alternator below 1000 rpm the charging light will stay on. When the bike is revved to 1000 rpm or higher the GEN light will shut off. When the bike reaches 3000 rpm the battery should charge at approximately 13.9Vdc."

That's exactly how mine behaves except I've set the regulator a little higher than 13.9 Volts. The only time that the revs at which the Gen light goes out should increase is if the battery is less than fully charged.

It'll be interesting to hear if magnetizing the rotor makes a difference.

[georgesgiralt]

Hello !
The purpose of the whole system is NOT to have a permanently magnetized rotor... This way, the output of the whole alternator can be tailored to the exact need of the bike and no more (and no less if the system is fit enough). If you permanently magnetize your rotor, the battery will get charged even when full and will, thus, either evaporate it's water or bubble if it's an AGM in both case shorten it's life ... drastically...
As per the charging light, it is wired between the generator output and the battery positive. So it will go out when the battery voltage comes ABOVE the alternator voltage.
This explain why after first cranking the engine (and depleting somewhat the battery with the huge BOSCH starter) the light only goes off at a higher RPM. When the alternator begin to charge, it gives all it's got in current to feed the battery and did not raise it's voltage until the battery recovers somewhat from the cranking. Thus if you have a new big battery and and a perfectly tuned engine, the GEN light will go off at 1500 RPM even after just cranking the engine...
I'm always amazed at how people do not understand automotive electrics and try to "simplify" or "improve" a perfectly designed and efficient charging system (which only flaw is that it was designed for simple and low power electrics of the era)
P.S. : You should check that the GEN light bulb is of the correct wattage to provide the system with sufficient current to get started... Stick with the specified bulb as per BMW instruction and everything should be fine...

[Semper Gumby]

Hello !
<snip>
I'm always amazed at how people do not understand automotive electrics and try to "simplify" or "improve" a perfectly designed and efficient charging system (which only flaw is that it was designed for simple and low power electrics of the era)
P.S. : You should check that the GEN light bulb is of the correct wattage to provide the system with sufficient current to get started... Stick with the specified bulb as per BMW instruction and everything should be fine...

Ah controversy.  

1) But I have had this problem for years.

2) I ride year round and I am NOT interested in having to run my Boik at 3000+ rpms when it is -5'C just to get the alternator to "Light Off" first thing in the morning.

3) And recently I tried to put a friends 450 alternator parts on my R65 and it ran normally (light out at about 1500 rpms) so something is amis with the bits that are on my bike and NOBODY can explain it (not even Rick from Motoelectric from whom I bought the 400 watt alternator in the frst place). (The alternator parts would not switch on to his bike because the /6 is a 105mm alternator and the R65 is a 107mm alternator <sigh>).

4) GEN bulb bought from local BMW dealer via an BMW approved part number off a BMW dealer computer.  Part number checked with my parts manual for the R65 (march 1980).  

So - respectfully - PHIBBIT on you - I'm going to try this.  PS - I do understand what you are saying but I'm willing to risk overcharging the AGM battery because I have a voltmeter on my system and if it overcharges then I will see it.

[Barry]

Georges makes a fair point in that the output of a true permanent magnet alternator cannot be controlled by our type of voltage regulator. So I agree in principle with what he says but I doubt the slight magnetization achieved using the euromotoelectrics method would produce enough output to worry your battery. Once the voltage regulator senses an excessively high voltage it will shut off the current to the rotor leaving only the permanent magnet effect to provide a low level output which I would have thought will be more than consumed by the ignition system.

[Semper Gumby]

I understand the principle of what he is saying.

So I will make a concession and try to get Rick at Motoelectrik to look at the one part in this system that hasn't been changed: the stator.

Then all bets are off and I'm connecting the rotor to the charger.  I am frinkin tired of this problem.

[georgesgiralt]

Hello Semper Gumby,
Try to go at an auto part store and get a 12V 3W minimum wedge bulb (5W would be better). And try it on the R65 in a frisky morning.
I frankly doubt that your rotor stay magnetized using the procedure described on the Euromotorelectric web site. After all, it receive this treatment every time the bike runs...
But I was proven wrong many times in my life ....  :-?
Depending on the regulator you have installed in the bike, you may be able to adjust it a bit to start charging at a tad lower RPM than the stock.
I, would bet on the bulb being incorrect.
Edit : I doubt that the rotor stays magnetized a long time with the procedure given (not the proper material).

[Bob_Roller]

I've got the 5 watt lamps installed on my '81 R65, I believe it's SAE #194, the OEM lamp is 3 watts, SAE #168 I have not noticed any difference in the charging system operation .

[georgesgiralt]

Yes you're right.
These bulbs are made in 1.2, 2, 3 and 5 watt.
IMHO you need at least 3W to make the system works by the book.
As these bulbs have very faint markings and the difference between a 1.2 W and a 3W bulb is non existent, I suspect some of us have the wrong bulb installed and, thus, need a higher RPM to start the whole system. It is the cheapest thing to change/test... Provided you can find a real 5W bulb ;-)

[marcmax]

For what it's worth I had a similar issue on my 82LS but not quite as severe. First start of the day the light went out at around 2500rpm and then later it would drop to around 1500-1700rpm. I was just living with it since the bike stays on a battery tender when it the garage.

I decided to wire a resistor into the circuit as a backup for one day having a failed generator lamp. Side benefit is that the generator light cuts out right at 1000-1100 rpm ever time now.

[Semper Gumby]

I don't know what you guys are talking about.  You have got me chasing after stuff that doesn't exit.  The freekin GEN bulb in my R65 is not a #194 or or a #168.  It's a tiny thing you can't even get at an Autozone.  That's why the last time I bought one I went to the dealer.

Where is my parts manual?  

OK - The part number for the bulb that fits in my R65 is 07 11 9 978 375.  It is listed as a 1.2 Watt bulb and you are telling me that in order for the Bosch alternator to work properly I need a 3 or 5 watt version of this bulb.  Why would BMW sell me a bike with the wrong bulb in it?  Are you guys sure on this?

[marcmax]

I understand your frustration. This question seems to be under attack from a dozen different directions. I still think the resistor in the circuit is the way to go. Monte has a great write-up in the Technical FAQ and it literally costs pennies to assemble and install. No question about what bulb, wattage, etc at that point. It puts the exact resistance load needed into the circuit, bulb or no bulb.

I also picked up a solid state voltage regulator at Advance Auto Parts. Generic replacement, just matched it to the old BMW part. Haven't had a charging system hiccup since. Do I know the why and details behind it? Not a chance. But between the two I think I spent about $10 and have never looked back.

[Barry]

Well believe it or not BMW specified a 1.2W Gen lamp up to 1980 and a 3W lamp from 81.  Can't think why they changed it.

A 3W lamp will be approx. 48 ohms so you could try substituting a 48 ohm resistor to see if it makes any difference. You won't actually find a 48 ohm resistor as it's not a preferred value. 47 ohm is commonly available and would be fine.