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Post a pic of your Airhead

Stuff2C said:
Screwed up and sold this one :cry

AHH, I feel your pain! That is a nice looking rig! California Friendship1, and is that an S bike, or an S fairing on a R bike? Any mods to the bike to make it more sidecar friendly?
 
First Post

And first bike too. I am new to motorcycling, just about 2 weeks or so, and have just this 1974 R90/6 to show. I am thoroughly enjoying my time atop it, though my new battery has mysteriously died. I've heard of problems with the charging systems in the early BMW's, is this true? Is there any way to fix it? Also the front brake is a bit dodgy, though I manage. And finally, I do indeed have the front fender (minorly cracked however) and all the mounting brackets, but no bolts to secure everything in place. Any help in locating said bolts would be greatly appreciated. I hope the picture loads, or you all just read this long-winded post for nothing.
 

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Have fun! You should:

- put a voltmeter across the battery with the engine at say 2.5 to 3K RPM. You should get near 14v. If not, then the you'll need to figure out why. Sometimes it's the battery (do you know the history of it?) but most likely it's the alternator. Get with Rick at Mottorad Electrik for his book on boxer charging.

- bleed the front brakes

- go to the dealer for the bolts. You've got an aftermarket fork brace...you might need additional bolts to mate with the fender...I'm not familiar with exactly how the brace and fender work together.

Kurt in S.A.
 
Fender Brace

Nice bike. Don't let the electrics get you down. It will be a PIA until you fix it properly. Could be the brushes, voltage regulator, but most likely an alternator...possibility that the diode board is bad....but then, consider it an opportunity to learn. Start as you have been directed with the volt meter....

As for the frender brace?
 

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Thanks for the replies

I'm thinking that it probably isn't the alternator, because my bike ran beautifully after being jumped (I just happened to be at an auto parts store). I used to have an old car that had recurring alternator problems, and the car just wouldn't run until I replaced the alternator. I checked out the Mottorad Elektrik site and that 400 watt charging system seems to be what I need. I don't really rev my engine too high and have just been riding around town, no highway, so from what I gather perhaps my charging system has never turned on at all. I'll check it with a voltmeter, but the battery was brand new, and I just don't think that is the problem.

Thanks!

(I usually don't post on forums, just lurk, and am apparently much more long-winded than I would have thought . . . sorry!)
 
Lurking is free but, posting is what keeps this forum going. :thumb

If you have a question, don't be afraid to ask. There's lots of help in here. :D
 
Long winded?

Ha! Wait untill you try to wade through most of our stuff. On the electrics: Keep an open mind and an open ear to those who have been there. The car experience isn't necessarily applicable (DAMHIK). You *will* have electrical problems...until you fix them. Without the headlights on, Airheads travel a pretty long time on one battery charge. On a full charge, the only way I ever knew about charging problems was the Volt Meter, which is always suspect, or the dreaded "flickering" GEN light. That is, until the bike either didn't start at the worst possible time....or simply stopped in it's tracks after a few feeble stutters. There's an expensive way...and a cheaper way. If you want to start simply, attach a volt meter that you know works, across the battery terminals, duct tape it to the tank and go for a ride. Watch out for trees.....If you want to do it (check for charging), go to Snowbums Pages and read the comprehensive testing procedure.

Long enough post?

Here's the bike I passed on to a family member....Still get to ride her....
 

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The alternator doesn't really "turn on" strictly speaking but puts out higher voltages as the RPM gets higher...up to a point. You're battery will charge if the input voltage is 13v but it'll take a long time. It charges better and quicker, and prefers to have a steady voltage well above 13.5v. If the voltage is too high (14.4v or so) for too long and you'll boil the water out of the battery, so there is a happy medium in there somewhere.

IMO, for the price of a new charging system and all the "hassle" of installing, etc., I'd invest in a smart charger like the Battery Tender. Or for less than $10 (on sale), I bought a float charger at Harbor Freight. It's designed to charge the battery at a good rate and then go into "float" mode where the charging current drops off to maintain a charge. Buy something like that and hook it up when you're not riding the bike to make up for what the alternator can't get done because of your riding style. You might be able to hook up permanent connectors or use an accessory plug on the bike to make connecting the charger easy.

Kurt in S.A.
 
Semuta, those ATe brakes do require adjustment every now and then. I don't know the exact procedure but I've seen it done at a tech session and it's not hard and the riders reported that it made a real difference.
 
20774 said:
The alternator doesn't really "turn on" strictly speaking but puts out higher voltages as the RPM gets higher...up to a point. You're battery will charge if the input voltage is 13v but it'll take a long time. It charges better and quicker, and prefers to have a steady voltage well above 13.5v. If the voltage is too high (14.4v or so) for too long and you'll boil the water out of the battery, so there is a happy medium in there somewhere

Kurt in S.A.

In fact, the alternator DOES turn on. When the battery voltage drops below a low limit, say 11.5v, the voltage regulator directs battery voltage to the rotor via the brushes. This "excites" the rotor, turning it into an electro-magnet spinning inside the field windings of the stator, inducing alternating current. When the battery is re-charged to a high limit, say 13.5v, the voltage regulator cuts off voltage to the rotor. If the regulator fails on the high side, 4000 RPM might produce a voltage reading across the poles of the battery in excess of 17v.

You'll know when this happens too, because your battery will be dry in the cells closest to the + and - posts and you will have been popping headlights for at least several months.
 
Semuta said:
I'm thinking that it probably isn't the alternator, because my bike ran beautifully after being jumped (I just happened to be at an auto parts store). I used to have an old car that had recurring alternator problems, and the car just wouldn't run until I replaced the alternator. I checked out the Mottorad Elektrik site and that 400 watt charging system seems to be what I need. I don't really rev my engine too high and have just been riding around town, no highway, so from what I gather perhaps my charging system has never turned on at all. I'll check it with a voltmeter, but the battery was brand new, and I just don't think that is the problem.

Thanks!

If your diode board is failed, your bike will be running on alternating current. The bike will run but the battery will not re-charge and will go dead after a few hours of use. The diode board is under the front cover along with the alternator and the points. NEVER REMOVE THE FRONT COVER WITHOUT FIRST DISCONNECTING THE BATTERY - TERMINAL.
 
Photo

I'll try to show ya'll mine
attachment.php
 

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mines...

I've got a 1973?¢ R75/5. Currently running a 1974 /6 tank. New valves and one size over on the pistons. It's my daily rider, but isn't without it's problems... All in all it's been a reliable steed.

This photo was taken on October 05, 2006 in Sun Valley, Calif. at a friends house just before riding to Cottonwood, Ariz. to check out the First Annual Western Horse Magazine Smokeout. With the exception of having to patch the rear tube on a Sunday, the bike ran great at 80 to 100 mph for most of the 1000 miles we did that weekend.
 

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1978 R100/7

I found this beauty in Florida with less than 1000 miles on it. It cleaned up real nice.
 

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