The battery has died in my '85 K100. I am open for suggestions for a replacement. I see the recommended Motobatt is over $200

Steve get on to fleabay and onto a seller 3RD Gear he sells Motobatt at somewhere close to a reasonable price. He has none listed at the moment but may have some. Or get the Motobatt catalogue on line and there is a smaller one that fits and does the job well its about 20 amp/hr. I have one in the K75 and it works just fine, the big one the Ks have is overkill.
I have a 30ah Motobatt only because I run a CPAP machine from it when I am camping and it runs it for 3 nights and still starts the bike.

Hi Rick, that would be the MB51814 which is listed for some of the early BMW twins? A quick look on the internet shows them to be around the $107 dollar mark which sounds better.

STEVE1959 wrote:Hi Rick, that would be the MB51814 which is listed for some of the early BMW twins? A quick look on the internet shows them to be around the $107 dollar mark which sounds better.

Yep MB51814 thats whats in the K75 and it starts just fine. Those will deliver just a tad more cranking amps than the OEM battery.

Hi Rick, Third gear had them (the MB51814) listed at $122.00 on Ebay including delivery. They suit a few BMW including the new 1600. I rang my local dealer to see if he had one but he isn't selling them (Motobatt) anymore because of some trouble the distributors are having at the moment. So I have ordered it from Third gear. Thanks for the information, will let you know how well it spins the old girl over!!

Just looked. I have a 61212346800. Maintenance-free gel battery 19 Ah Exide branded by BMW. Installed in BMW motorcicles since 2003.

Not had a problem starting the bike and after the strip down it took some cranking to get it going again. Holds a charge really well also/

Exide 53030, 30 Ah - 90 USD - 2 years warranty

There are all sorts of exotic battery types around but simply get the highest Ah rating you can that will fit (usually about 30 Ah) and pop it in. I like Yuasa batteries they have always worked well for me. Don't forget when you get a dry charged battery and fill with acid give it the conditioning charge before you start the bike if you want the maximum life from it.
Regards,
K-BIKE

I have very good experience with an Odyssey PC680.

I have never tested a Odyssey battery, but as a member lot of different BMW forums....
I can report that it is a lot of satisfied users/owners around.

It`s the cranking power that should be especially good on these ones,
compared to others.......

But have also read that they don`t function that good in the cold, below 0^oC.

I've been using Odyssey batteries for a number of years now. No trouble in the cold. My coldest start 18 degrees F. after a night of camping. Which I personally think is too cold for motorbike riding. By the way my buddy's bike did not start!

The Motobatt battery arrived today and I just installed it, no drama's fits straight in. Turns the old girl over pretty quick and she fired straight up, can't wait to get out for a ride! The number if anyone is interested is Motobatt MB51814 22ah and 260cca, the cost delivered from Melbourne was $122.00aud. Thanks to everyone who responded to the post.