R69S alternator conversion

Restoration forum Bmwbike.com
Pierre Michaud

R69S alternator conversion

Post by Pierre Michaud »

I am looking at the possibility of converting the 6 v generator system on my R69S to an aftermarket alternator system as offered by Motorrad Elektrik.One of my concerns is the adaptability of this system with respect to the vibration damper on the R69S. I've been told that a longer Allen bolt is needed when installing on R50's and 60's.....will I need to discard the damper or does the kit have the necessary fastener......will it clear the front engine cover? I would welcome anyone who has gone through this conversion specifically with an R69S and or any other pro's and con's related to the conversion on any /2!

Pierre
J. Stracco

Re: R69S alternator conversion

Post by J. Stracco »

I've done this conversion. It is very easy. The only problem I had was the vibration damper rubbed against the the brushes on the alternator. You could shim it out without too much problem. I'm not sure if the dampener would touch the cover or not. I didn't bother to shim it myself, but just left it off. (I have an R50/2. I was just putting the dampener on to see how it would fit. When it looked like it wouldn't I just left it off, because that bike didn't have one anyway.)
J. Stracco

Re: R69S alternator conversion (More)

Post by J. Stracco »


As far as the bolt goes, you can either shorten the threaded end as recommended in the intructions. I choose to use some washers to fill in the gap. It worked well and never touched the cover. But being that several different cover shapes were used over the years, you might want to check the clearance before running the engine.
Pierre Michaud

Re: R69S alternator conversion (More)

Post by Pierre Michaud »

Thanks John, sounds like a plan. I was mistaken when I said it needed a longer bolt. So my concern of rubbing against cover was unfounded. I too prefer adding a shim/washer in lieu of shortening the bolt. But now you have come up with a new element I was not aware of....rubbing against alternator brush.....I have no choice as the damper was put there for a good reason on the R69S. Perhaps I can shim at that end rather than at the bolt head interface or maybe I don't need the damper since I will be running a sidecar unit and revs will be pretty much below solo riding!
J. Stracco

Re: R69S alternator conversion (More)

Post by J. Stracco »

Pierre-

The dampener disk itself rubbd against the brush housing. Possibly one or two
additional washers dropped inside the front end of the alernator would
back out the bolt and the disk enough to solve this problem.I'd be careful about
the rubber in the dampener dryin out though as that might change the whole game!
Too many washers probably wouldn't be a good idea eithe...you need some thread
to hold that bolt on.

I should add that of the many modifications I have done to my bike, other than mirrors, the 12V conversion is the one I think is most worth it. There is a noticable difference in the brightness of the lights. I also swapped out the headlight reflector and lens for an R65 setup which fit perfectly and allowed me to use H4 halogen bulbs which are REALLY bright.
Supposedly the alternator rotors were factory balanced, which the /2 generators were
not, so you might notice some new smoothness. If the rotor has been rewound,
then who can say if its balanced?

I also found that the instructions called for drilling an off center hole in the breather
cover to allow the harness to pass through. I put my whole right behind the original
harness hole and managed to squeeze the new wiring in there...barely!. It worked
and looked like one harness when wrapped in tape.

Hella also makes a 12V horn which is very much in the original style.

If you have any luck in finding a 12V black case battery like the original, let me know!

Pierre Michaud

Re: R69S alternator conversion (More)

Post by Pierre Michaud »

John,
Thanks for the valued info. I will let you know how I made out....once I figured out how to scrounge another $500 without my wife noticing! It's amazing how bills pile up when you want to do a proper restoration using latest technology without sacrificing original appearance!
Mike Etson

Re: R69S alternator conversion

Post by Mike Etson »

Well, here is another take on the 12v conversion. I looked long at the same procedure, and for the express purpose of improving the lights. What I ended up doing instead is buying a H4 reflector/bulb assembly and a 6v H4 bulb. Cost about 25 bucks, and I am very happy with it. The bulbs are identical to standard H4's, but designed for 6 volts. 60 watts low, 55 high, and about as bright as the 12v setup. The wires dont get too hot, and generator handles it no problem. So I figured, why bother spending 500 bucks and modify more than you have too?
J. Stracc0

Re: R69S alternator conversion

Post by J. Stracc0 »

I used to run my bike with a "step up" regulator which gave 12V at 60watts.
The problem that I ran into, and which may apply in the 6V halogen situation as well,
is a lack of watts.

I run with my headlight on all the time. I know alot of people don't, but I feel that it's
a good safety precaution. With a bright 60W bulb in the headlight this would mean that
there would be a constant 60W drain as per the 6V halogen conversion or a 35W drain
with a stock configuration. The taillight takes another 20W. Which leaves
the license, speedo, neutral, charging, highbeam indicator, brakelights, turnsignals and
horn. All in all, the 60W generator put out JUST enough power for all this with the
stock wattage configuration, but a more powerful headlight was out of the
question.

The alternator conversion gives 280W at 12V, more than enough for all the electrics and
a nice bright halogen headlight.
Pierre Michaud

Re: R69S alternator conversion

Post by Pierre Michaud »

Mike,

The reason I am going 12 volts is 3 fold:

1. I hate generators and mechanical rectifiers
2. I need more Watts for sidecar accessories
3. Alternators give constant current flow at all
RPM's and there are no brushes spreading carbon
dust all over the ignition system under the
front cover.

I also think that compared to generators alternators are virtually maintenance free!

So if the conversion works then I will go alternator....if not then your option is the best I've seen for a 6 volt system....another one would be to put a Honda 120 volt gas generator in the sidecar that would also act as ballast when riding without passenger!
Pierre Michaud

Re: R69S alternator conversion

Post by Pierre Michaud »

Mike,
Just a precautionary note here with regards to wires not getting too hot. If you are noticing that heat is being dissipated through the wires with the halogen conversion you might get into trouble down the road as in the long term the wire insullation of the lines feeding your bulb will get brittle and eventually crack.....which may then lead to shorting and God knows what else!
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