A question heard fairly regularly seems to go something like:
I've had an intermittent problem starting the bike and with the lights. Sometimes with the key on the headlight and instrument lights will not come on (the neutral light will come on if it's in neutral). When I push the start button nothing happens. If I put the bike in gear, let out the clutch and rock the bike back and forth the lights will flicker on and off. Once the headlight stays on I can start the bike. While I'm riding the headlight may flicker or go out for awhile but the bike seems to run fine. What's wrong? Do I need a new starter?
This is fairly common. The Load Shed relay, which controls the lights and such, is grounded thru the starter. If the starter is all loaded up with dust from the brushes (they wear over time), you will not be able to ground the relay and the lights won't come one. By the same token, you won't be able to run the starter!
When you put the bike in gear and rock it back and forth, you're also causing the starter to rotate (when the bike is rocked backwards). This movement tends to clear the dust from between the starter rotor and the brushes and (temporarily) cure the problem.
The long-term cure is to remove, disassemble and clean the starter. This is pretty straightforward operation.
First, remove the battery ground and positive cables - IN THAT ORDER - and remove the battery (it's been a while, so I'm not sure if it's required that the battery come out for clearance purposes, but it will make your job easier). Remove the cable from the starter.
Remove the two socket head capscrews retaining the starter and pull the starter to the rear to remove it. It's a tight fit into the bellhousing, with an O-ring, so rotating it slightly about the shaft axis will help you "wiggle" it out.
Next, you need to disassemble the starter.
There are two long screws (or three?) which go from one end cap to the other. Mark the position of the two end caps relative to the stator body (I use a scribe to scratch a line across the mating surface).
Remove both screws and carefully pull the drive end cap from the starter body (that's the end with the gear). Note the presence and number of any shims installed there - they must be put back!
Now you can pull the brush end cap off and remove the rotor from the stator. It's kinda tough to do, as there are some fairly powerful magnets in the stator which pull the rotor to one side. Just slide it out.
Clean the dickens out of everything, using a cleaner which will NOT leave a residue (some "contact cleaners" will leave gunk behind). Brake cleaner is one of my favorites.
Inspect the rotor contacts and the brushes. I think the minimum brush length is about 1/4" (memory fails me here, that's probably wrong). At any rate, the odds that the brushes are worn out is somewhere between slim and none, so don't sweat it too much.
Assembly is the reverse of disassembly. I insert the rotor into the stator and then install the brush end cap, aligning it with the marks I made earlier. Finally, install the shims and the drive end cap, align to your marks and install the long screws.
Install the starter and battery, hook up your cables and you're set!
SKYLANDS BMW RIDERS
HOME | CALENDAR | PHOTO ALBUM | HISTORY | NEWSLETTER
All contents Copyright © 1996 - 2014 Skylands BMW Riders
|Maintainer: Tom Coradeschi WWW - email
Last Update: 10 June 2007