• Welcome, Guest! We hope you enjoy the excellent technical knowledge, event information and discussions that the BMW MOA forum provides. Some forum content will be hidden from you if you remain logged out. If you want to view all content, please click the 'Log in' button above and enter your BMW MOA username and password.

    If you are not an MOA member, why not take the time to join the club, so you can enjoy posting on the forum, the BMW Owners News magazine, and all of the discounts and benefits the BMW MOA offers?

  • Beginning April 1st, and running through April 30th, there is a new 2024 BMW MOA Election discussion area within The Club section of the forum. Within this forum area is also a sticky post that provides the ground rules for participating in the Election forum area. Also, the candidates statements are provided. Please read before joining the conversation, because the rules are very specific to maintain civility.

    The Election forum is here: Election Forum

K1100RS Alternative Alternators

B

bwoods1100

New member
Hello all. I have about 800 miles on my new to me k1100rs (121xxx miles). Today whislt riding home the alternator area began making a very loud rattling noise. When I got home (5miles later) I found my bike would not start due to dead battery (brand new oddysey battery). After charging and starting the bike I preformed a voltage test and found I was getting 11v with the bike running(dead alternator). Does anyone know of affordable sources for replacement alternators? Beemer boneyard is unfortunately sold out. Also, has anyone heard of db electrical? They claim to make an alternator for this bike. I'll post a link below.
 
Pull the alternator off and check the coupling between the alternator and the engine. It's not hard to pull off. It may save you from replacing the whole alternator.
 
kioolt said:
Pull the alternator off and check the coupling between the alternator and the engine. It's not hard to pull off. It may save you from replacing the whole alternator.
Click to expand...

Brushes would not cause a very loud rattling noise, but could cause it to stop charging. Deteriorated coupling dampers could cause some loud racket, but would it cause it to stop charging?.

alternator k1100.jpg

Next step is definitely to pull it. Then he can check the coupling, bearings, and brushes. Most likely, repair will be a better alternative than replace. An auto parts store might be able to spin it up and check output.
 
Alternator issues

If the alternator rubbers have completely deteriorated, then it's metal on metal and the vanes WILL wear down so far the alternator won't spin...then you need to replace the cup as well as the rubbers.
 
My new Euroelectrics alternator is installed and now im getting odd voltage readings. At idle, my voltage reading is 12.2v. I have a steady climb in voltage until it peaks at 14v at 4000 rpm. Is this normal ? I wasn't sure if these bikes have a voltage attenuator that should keep the voltage constant at 13.5v
 
It should charge sooner than that. The voltage regulator is built into the alternator. Are you starting with a well charged battery?
 
It's a three month old Oddysey battery and the charge was good and cranked strongly. Talking to the previous owner, he says that the voltage fluctuation between idle and higher RPMs was a known issue on the older bikes. We don't really know that much about the older bikes which is why the OP posted the question last night.
 
beemermyke said:
...Talking to the previous owner, he says that the voltage fluctuation between idle and higher RPMs was a known issue on the older bikes.
Click to expand...

This is the same Bosch alternator used in the oilheads. I don't recall that tendency on any of my oilheads or K's. I have changed the voltage regulators inside the alternators to get 14.2 volts instead of 13.8 to better suit AGM batteries, but they have all charged strongly from 1500 revs. If by "older bikes" he means airheads, then yes, they were known for that but that is a completely different technology. K's? I haven't seen that.

With a good battery, and now two alternators, the behavior is pointing towards connections. I would check ground resistance from the battery strap to the central ground under the tank. While at it, I would clean, de-ox, and reattach the grounds. I never did hear a follow-up on where the noise was coming from. How did that resolve?
 
The noise is gone (sorry for the lack of follow-up, it's been parked awhile due to work commitments). We checked the voltage at various RPMs this morning to see what the differences were. At idle, 12.4V, 1000 RPM, 13.3, 1500 RPM, 14.4. Since my son Bwoods1100 put this bike together from a basket case and didn't have much to go on, we'll recheck battery strap, etc. and clean things up as needed.
 
beemermyke said:
The noise is gone (sorry for the lack of follow-up, it's been parked awhile due to work commitments). We checked the voltage at various RPMs this morning to see what the differences were. At idle, 12.4V, 1000 RPM, 13.3, 1500 RPM, 14.4. Since my son Bwoods1100 put this bike together from a basket case and didn't have much to go on, we'll recheck battery strap, etc. and clean things up as needed.
Click to expand...

Those voltages are fine. 14.4 at 1500 is all you should expect.
 
12.4v means that your battery is not fully charged.

Your idle speed is also too low. Should be 1000-1050 rpm.



:dance:dance:dance
 
Alternators for bricks

Just as more tech info and alternative sourcing for alternators for the Bricks. Rebuild yours.
http://lunaindustriesinc.com/

I have been using these folks for over 30 years. They 'zero' time my starters and alts for about $75-90 each. Very happy with them.
Danl
#129878
 
You must log in or register to reply here.

Similar threads

akbeemer
Battery Woes
Replies
17
Views
938
globalrider
globalrider
K
99R1100RT starting electrical gremlins
Replies
11
Views
1K
pauls1150
pauls1150
globalrider
Original YUASA YTZ14S - Finally Quit
Replies
16
Views
2K
oldcamper
O
G
Battery Replacement
Replies
8
Views
1K
Omega Man
Omega Man
C
2004 K1200GT - Ahhh, the clutch
Replies
4
Views
1K
ts888
ts888
Back
Top