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Sometime in the late 80's, BMW changed manufacturers for the GS starter in an effort to get more reliable starting with a starter that would spin faster. They contracted with the French company Valeo, the same folks that make starters for Saturn (in fact, the motor is interchangeable with the BMW part if the reduction gear assembly is swapped over). All seemed OK at first, until Valeo starters here in the 'States and other hot climates started spitting out the magnets that surrounded the rotor. The old Bosch starters never exhibited this problem, and are rebuildable as well. When a fellow a few tables down at a club swap meet offered me one from a pile he was selling for a friend, I was on my way (I swapped him a pair of Roadmaster leather winter gloves for it).
 Once home, I confirmed the starter would work by a) counting the number of teeth on the gear and comparing it to the Valeo installed on the bike (both had 9 teeth), and b) hooking it up to a truck battery with some jumper cables to verify that the starter solonoid engaged and the rotor would spin. I then boxed it up and sent it off to Motorrad Elektrik for a rebuild. Rick Jones replaced all the bushings, cleaned/trued the commutator, and repainted the housing before sending it back. Cost, including shipping both ways (the thing weighs a ton), was about $100. Sure beats $350 for a new Valeo time bomb!
The rebuilt Bosch (left) is shown in the photo next to the Valeo it replaced (the Valeo's a spare, and has already been used once to get a friend going again while he chased down another Bosch). As you can see, Rick makes 'em look almost new. Also note the bracket at the lower end of the Bosch, which you'll also need because the Valeo doesn't come with one. The starter sits on top of the engine under a cover. Pop the tank off, then remove the top of the air cleaner and filter. Remove the two socket head cap screws that hold down the cover and remove it. You'll see the Valeo starter near the front of the engine.  Only two bolts hold the starter in, and they thread through the engine casing directly into the starter housing. Quarters are tight, and you'll likely end up using an open end wrench and turning them 1/6 turn at a time. It'll take a while, but they will eventually come out, so be patient. Remove the starter cable from the starter solenoid at the big copper nut, then lift out the old starter. If it's still working, you might consider keeping it on the shelf for a spare in the unlikely event that the Bosch ever gives up. Or you can flog it on the IBMWR site to some poor devil looking to avoid a big bill at the BMW dealer. Either way, set the old starter aside and clean up the top of the motor in preparation for installing the Bosch.
The Bosch mounts to the same holes as the Valeo, but the bolts use through holes in the Bosch starter housing. That means you'll have to provide a couple of nuts for those bolts (blue arrow below).  The support bracket on the front end of the Bosch starter slips down over the forward side of the engine case and lines up with another through hole. You'll need one last bolt and nut for this location. Use a socket head cap screw so you can get on the front end more easily (blue arrow in photo below). Clearances are tight in this area, and you need to be careful to align the starter with the engine housing correctly. Don't force anything, as it should all slip into place. One possible exception is the support bracket at the front of the starter, which is easily bent when the starter is off the bike. If you need to, you can straighten the bracket with a vise and a large adjustable wrench.
 Connect the starter cable at the big copper nut and you're ready for a smoke check. Assuming your battery is in good shape, a stab on the starter button should have your motor purring in just a few seconds. That raspy shriek of the Valeo will be replaced with a turbine smooth whine, and you can leave home secure in the knowledge that you won't need a bump start to get back. |
