Bosch starters up through 1974 were 8 tooth 0.001.157.007, rated 0.5 hp and 290 A.  The /6 bikes for 1975 and 1976 used
an 8 tooth 0.001.157.015 rated 0.6 hp and 320 A.  The 8 tooth starters are used ONLY with the 93 tooth flywheels; and are
for all practical purposes, interchangeable.  For 1977 and later, the starter has to be 9 tooth, for use with the 111 tooth
flywheels (or more properly called the clutch carrier from 1981).  The starter is 0.001.157.023, rated 0.7 hp and 320 A.   
Solenoids, unconfirmed, seem to be the same as EARLY air-cooled VW.   When overhauling a Bosch, I usually replace the
Bendix, the bearings, the brushes, undercut the armature and make sure it is round and semi-polished, and replace the
solenoid assembly.  Your choice on what you do. 

NOTE:  The "Airheads Beemer Club" had an account with Ace Houston Warehouse, a wholesaler/importer/remanufacturer, ETC. 
The Club account is #700.  Call Bob Spencer at 1-800-392-3332  or e-mail to acehoutx@flash.net.  Mention account 700. 
Per information I received from a fellow Airhead, the part was D6RA15, Valeo changed it to 432586.   This is supposedly a brand NEW starter.  There was no core charge, but they will or might pay shipping to get your old one.    I do NOT know if this is the latest updated Valeo with the safety clips for the magnets!!  They may still rebuild Bosch starters (??), last price I got was $200 and a $100 core charge and shipping (core charge refunded).   Bob Spencer thought that the Bosch starters MIGHT be put back into production at some point.   Quite frankly, I have not had a good reason to deal with these folks.,...that is, I have had NO dealings with them.  I consider the prices a bit high....and I think their stock of starters may be getting thin anyway.  NOTE!  The above information is supplied as a courtesy. 

****I HAVE had dealings with John Rayski at www.euromotoelectrics.com and I CAN recommend him for Bosch starter (and other parts) and for Valeo starters (yes, brand-new updated Valeo's).  He has the proper Valeo starters with the updated magnets and clips; his prices are good, he offers free shipping (on some orders...and can be quite a savings on a heavy starter)....and he is knowledgeable about the use of these in our Airheads.  He is the same person who makes and sells the EnDuraLast alternator conversion for BMW airheads and for MotoGuzzi's.  He can supply you with proper spark plugs and a lot of other things.   Look at his website:
www.euromotoelectrics.com

Although I have a wholesale account with John, I am no longer in the business of supplying parts and services, except in a rare instance.  I prefer you go
to such as Ted Porter's Beemershop    www.beemershop.com  or direct to www.euromotoelectrics.com


Be sure to use the Bosch (or other) starter with the proper number of teeth.   The Bosch starters have a bent metal plate at the
forward end, using one bolt to the timing chest wall.  This supports the starter to the timing chest wall, needed with the Bosch. When
installing a Valeo in place of a Bosch, do not use the the plate nor bolt, and the Valeo installation is maybe 6 pounds
lighter than the Bosch. When installing a starter be especially careful that the starter is properly and squarely mounted,
you want to avoid breaking or otherwise cracking the nose (the casting that is the rear part over the flywheel) during
operation.  Be sure the mounting cradle, nose area, etc., is CLEAN of filth and proud metal, etc.  See later on that subject
in this page.

The Airhead Bosch starter uses ELECTROmagnets, not permanent magnets, for the field coils. Bosch does make a
permanent magnet starter, but I have never seen one in the Western Hemisphere.

The Bosch electromagnet starter is very old-fashioned technology, rugged, very reliable, but less powerful than the permanent magnet
high rpm with planetary gear type like the Valeo.  A nice property of the Bosch field coil type is that as it 'sees' a heavier and heavier load (cold
engine, thick oil, etc), it draws more and more current, producing more and more power.   Still, the ultimate power is less
than the Valeo, which spins faster, and has the planetary gear reduction drive inside.   I consider it a tossup as to which
is better, considering all factors.   The Valeo parts are somewhat less rugged, but that appears not to be any big factor,
even over many miles.

It has been theorized that the Valeo permanent magnet type MIGHT loose some magnetism over TIME and USAGE.   However,
they have held up surprisingly well....and I have had NO reports of this problem. I would suggest ignoring this 'supposed' problem.
 

The Valeo Starter, and some Bosch information:

We all know about the magnet failures on the early Valeo's.  Using epoxy to glue magnets may have its place in this world, but there
were lots of failures, especially in Airheads where the starter is subject to so much repetitive heat cool cycles and just plain engine
heat by direct contact.  I do NOT like the ideas of epoxies being subjected to constant wide temperature changes, their
expansion-contraction rate is vastly different than the surrounding metal. The starter in an Airhead does, remember, sit right on top of the
engine, inside a cover!   The constant heating and cooling cycling can crack or otherwise ruin the bond of the magnet glue.  
Valeo addressed this problem (in 2001) by changing the type of glue and reshaping the side of the magnet that fits against the starter shell.
....and late manufacture Valeo starters are adequate and seem reliable.  BUTTTT:

There is an aftermarket type of Valeo housing available with a modification to help keep the magnets from moving,
spring-type separating pieces (clips).   Valeo permanent magnet starters....as well as permanent magnet starters from many
other manufacturer's, even Bosch, work fine in cars.   The proper aftermarket Valeo's with the updated magnets,
bonding, and clips, are available from www.euromotoelectrics.com
 

In the past I have been outspoken in that I personally preferred the Bosch electromagnet type for our Airheads.  However, I am open-minded
on the latest Valeo starters (especially those from euromotoelectrics)....and think them now OK....so, if you are making a decision between
overhauling your Bosch, or replacing it with a Valeo.....or; replacing a Valeo with a Bosch....I no longer have any especially strong preferences
for the Bosch over the Valeo (or the aftermarket Denso, for that matter).  For sure, overhauling your existing Bosch starter, assuming the armature
is not going to have to be replaced, is going to be much cheaper than replacing it with a brand-new 'anything else'.  The stock Bosch starters are perfectly adequate.

For starters, or for parts for rebuilding, etc., see www.euromotoelectrics.com, John Rayski.  This is for both Bosch and Valeo.
John knows the in's and out's of all of them, and has a stock of all the pertinent Bosch and Valeo parts; and has Valeo starters
of the correct type in stock.  You MUST tell him if you need a 8 or 9 tooth starter.  

The Bosch is a common starter for many starter repair shops, easily worked on...but some may not have the parts for the
starter used in our Airheads.     The same sort of comment could be made about the Valeo and Denso.

You may run into information leading you to think about using a Saturn housing when rebuilding an original troublesome
Valeo.  Unless you are trying to save the absolute maximum amount of money, I recommend you get a new upgraded version
Valeo from www.euromotoelectrics.com   Or get them to fix you up otherwise.
 

Going from a Valeo to a Bosch and vice-versa:

If you decide to change your failed Valeo to a Bosch:  Brand New Bosch's are very pricey and probably not available. Try to find a
good used one, and rebuild it. Generally you need only a set of brushes and bushings (bearings) and a solenoid assembly.
If the Bendix drive is questionable, replace it.  The solenoids can often be rebuilt too but I do NOT recommend it, although I have
the information in this article.  You may have to undercut the armature, farm this out or do it yourself, it is not difficult.  YOU
MUST obtain and use the forward bent metal plate!

Keep the Bosch 'Bendix' drive lubricated. I like to use a silicone grease due to its general non-hardening and
wide temperature range. But, I have some mixed feelings about the use of silicone's on fast moving parts, and
maybe a lightly laced moly grease is better...I am NOT sure about this.  Starter rebuilders may have ideas.  

NOTE!: This is applicable to 1985-1988 models:

   There is a POTENTIAL problem, not commonly known, and there is even a BMW SI (Service Information, in other words, a Bulletin) on it, and the bulletin is 12-013-9 (2389).    If the original starter relay is the 61-31-1-244-019 (that's a BMW number, not a Bosch number!), it contains a diode, and has other properties that BMW thinks do not match the Valeo starter, & the relay contacts might stick.......and the starter continue to run!  

BMW says that the proper relay is 61-36-1-391-397, which has a higher current carrying capacity, and a stronger spring to help the contacts open.  If you have to replace the -019 relay, BMW will supply the -397 relay.    It also has the diode inside. Some have substituted generic 30 ampere relays.  NOTE that I have not actually heard of anyone having this sticking problem due to the starter-swap. I have heard of it happening due to sticking relay problems, but maybe only once or twice since I began working on Airheads!  So, it is a very rare event.  On the other hand, it is my belief that if there IS a problem with putting a Valeo into an Airhead that came with a Bosch, that the problem is likely only with 1985-1988 models.   To avoid confusion, if you have a pre-1985 Airhead, the stock relays seem to hold up just fine with the Valeo.  I have MEASURED the current draw of the Bosch and the Valeo solenoid coils under actual starter use, and they are NOT excessive, and are just about equal!  The inductive kick-back voltage is also comparable.  This solenoid coil current is the current that passes through the starter relay contacts.  I would not be inclined to replace the early stock relay, although I might open it and burnish the contacts.  Again..it is my belief that the problem, if there really is one (per BMW), that it is confined to the 1985-1988 models.

 

When retrofitting a Valeo to a BMW Airhead that had come originally with a Bosch starter, there can be an metal interference problem, which can be very slight and hardly noticeable, ...to more moderate.  The problem comes about because the starter nose machining is NOT EXACTLY the same between the Bosch and the Valeo starters themselves, and BMW was, perhaps, a bit more careful about machining the engine case when the Valeo was installed as the stock starter.   It is my belief that when BMW shipped their own Valeo starters on the later Airheads, that the machining on their Valeo nose might be very slightly different.  I have not made enough measurements to prove this.  I strongly suggest that ANY time you replace ANY starter, that you CAREFULLY check its fitment!!  There have been instances of a starter poorly fitted, and the nose breaking!

I THINK that this metal interference problem will be seen only when installing a Valeo in place of a Bosch, but I am not 100% sure about that.  So, my advice here is generic, and assumes you will check fitment of either Bosch or Valeo (and Denso, for that matter!, see much later in this article for that starter).   Frankly!!....I think that anytime you remove and replace even the SAME starter that was in the bike....that you should check for the proper fitment!!!

After you remove the old starter, LOOK carefully at the area the aluminum nose of the old starter had recessed into, just forward of where the gear mates to the flywheel (or 'clutch carrier', 1981+) teeth.   On some Airheads, BMW may not have cleaned up excessive metal over the last 1/2" or so of the round cavity, at the top inside edge. When you try to install the starter (probably this happens only with the Valeo, but I am NOT sure about that), you may find some combination of the following:

The starter does not fit perfectly, may not want to go fully downwards at that nose area and the Valeo threaded bolt holes (or even Bosch unthreaded ones??) may not line-up perfectly.   Inspect carefully, and use a half-moon fine file, or a small electric rotary tool of some sort, to make this inside area smooth at the top, with NO metal that is 'proud' (or of lesser diameter, causing a reduced diameter).  You can feel this with a fingertip, and usually see it with your #1 eyeball.   I have personally seen this and had to remove about .020" (+-), on both sides, at that top area.   This is easy to do, and then the Valeo (Bosch?) SHOULD fit/mount correctly.  

The Valeo, as opposed to the Bosch, has threaded holes, so you use the bolts you had from the Bosch, sans nuts, from the rear. 

Note the excess material at the left. Don't worry if
you remove a bit too much material!  DO NOT
remove material at the bottom. Since I can not
visually see YOUR installation, check how the
nose fits, very carefully, at ALL POINTS.  Use
a dentists mirror and strong light.


 

Overhauling the Bosch:

These Bosch starters are used in a variety of makes and models of vehicles. Sixties and Seventies VW's, for
one example.  They vary some, but are mostly the same.    So, it is not difficult, even at some auto-parts stores,
to get parts.  I do, however,  suggest you get them from www.Euromotoelectrics.com , so you can be sure of getting
the correct parts.

Not shown anyplace that I know of, is how to overhaul a malfunctioning solenoid switch. 
That is because most people will replace the solenoid.   A malfunctioning solenoid that has an open winding is
not repairable.  However, most of the time the problem is poor contacts inside; although poor contacts at the
brushes of the starter can make the solenoid act like it was bad.  Below are photos of a Bosch solenoid unit
as used on our Airheads. 

I have removed the terminal end cap.  To do so, you need a large soldering iron with a big tip.  Even a 35 watt
iron with a big tip will work.  It is the MASS of the tip that is important.  A very large soldering gun (perhaps the
275 watt size) might also work OK. 

You undo the 2 screws as shown, and then put a slight to modest amount of pressure on the end cap (as if
trying to remove it), whilst you heat the solder joints until they release.  Go back and forth to the soldering places;
until the cap comes off.  Clean up the solder holes. It is VERY important not to mix up which wire goes to what
terminal hole!!!...so watch them as you remove the cap.   DONT GOOF HERE!!!  The easiest way to avoid this is to
mark the end cap and body before removal!

Inside you will see the flat switch contacts recessed in the cap you removed....and the mating contacts held to the
solenoid with a funny 'nut'.  I usually don't bother disassembling further the plunger side. 

BEST way to clean the contacts in the cap and at the end of the plunger:  Use one of the very small rotary
stainless steel (or brass) cone-shaped brushes, that you can put in your drill press or electric drill.  They remove
very little material, and it takes only a few seconds at modest rpm.  An acceptable other method is with the flat
end of a piece of doweling or other tool, covered in 220 grit sandpaper. 

You MUST keep the contacts FLAT and square to the assembly, so maximum contact surface will be obtained.

There are 4 solid conductor wires.   The paired wires (push the insulation back a bit if you need to, to see the pair)
go to the battery terminal, and the single wire goes to the SPADE terminal.  DO NOT mix this up!   You've already
marked the case and cap so you won't mix them up, right?  There is one other wire that is spot-welded to the
metal end case.   The single wire next to it is the one that goes to the spade terminal.   You did note where the
wires went when you removed the cap?  If you goofed and did not mark the cap and body, the information here will
guide you to the proper fitment of the wires before you re-solder.

When re-assembling, you need to be sure the solenoid contacting plate fits into its mating cap depressed area
portion, and the wires go to the correct terminals!  You can assemble the cambric ring and the wires to the cap,
and lift the cap a wee bit, and rotate the tang at the far end of the solenoid, to line up the contacting plate with
the cap cavity.   Push against the tang end, holding the cap end, on your bench top, to be sure the contacting
plate actually moves into the cavity for it.  Assemble cap (align wires and pegs) to the plunger side of the solenoid
unit carefully, using #1 eyeball, and test that the solenoid plunger mechanically works OK with your fingers, then
screw the cap on with the two screws (locate the pegs!)...and THEN solder the terminals. Use ONLY a very hot
large tip soldering iron.  Use standard rosin core electronics solder.    Be careful to assemble correctly!

The solenoid should be tested with it mounted and connected-up to the starter.   Do the testing on the repair bench,
before you install the starter into the engine block.  You will need heavy gauge wires.  Connect the + terminal of the
battery to the battery large threaded terminal on the solenoid.  Connect the - terminal of the battery to a starter nose
mounting ear.   If you get a small spark from this, you miss-wired the solenoid!

Hold the starter...it will tend to jump around as it starts!.....and, using a jumper wire or screwdriver, etc,
momentarily connect the SPADE terminal to the + battery connection at the solenoid.  The solenoid
should clicking strongly and loudly and the starter should run.

Overhauling the Valeo

I was going to write up how to do this, but a fairly decent article with photos is on Anton Largiader's website, so here is the direct URL:
http://www.largiader.com/tech/valeo/

Note:  Valeo starters can be purchased from www.Euromotoelectrics.com; and they have parts for Valeo, and Bosch, and a few other things.  I highly recommend them (over Ace Houston Warehouse, which is mentioned in Anton's article as well as the one you are reading, well above this area).   Euromotoelectrics Valeo's are the latest type, with the modified magnets AND magnet clips.  NOTE the information and photo, well above, on fitting Valeo's to an Airhead that previously came with a Bosch.

 

The Denso Starter fitment problems:

It was reported to me that the Denso aftermarket starter, such as sold by Motorrad Elektrik, etc, does not fit perfectly.   I obtained a photo.  The installer noticed TWO problems with metal interference.
1.  Light interference with the solenoid to the starter cavity cover (rib on it).
2.  Interference at the mounting ear on the back cover.  In the photo, below, you can see that the ear has been ground down so as to give about 1-2 mm of clearance between the crankcase and the starter ear.

Revisions:
02/06/2004:  add link to /5 article; minor other clarifications
05/30/2004:  add NOTE on the starter relay changes
10/27/2005:  updated in numerous places
04/22-2006:  add red note on Valeo installation needing special relay
11/28/2006:  correct URL spelling for euromotoelectrics
11/29/2006:  Change to 16-A, and do minor editing (16-B is being written)
04/28/2007:  Fix actual hyperlink for euromotoelectrics, display had been OK, link NOT.
09/28-10/1/2009:  Update hyperlinks, clarify some details that were unclear; re-arrange article a bit for additional clarity, add
                       all the information on the Bosch Starter solenoid overhaul.
10/17/2009:  update with photo of the metal interference problem.  Clarifications and editing throughout article.
11/23/2009:  Add reference to Anton's site for the Valeo overhaul, euromotoelectrics in that same area, etc.
04/25/2010:  Add photo and information on the Denso problem
05/24/2010:  Fix typo regarding forward plate that IS used with Bosch, and NOT Valeo.   Clarify a few minor details.
05/12/2011:  Fix typo where word alternator should be starter. Add dividing line at one place to clarify a new discussion section that was confusing. Fix a couple of mis-spellings.
                        Remove hyperlink to 'thisoldtractor site that has removed the starter motor overhaul information.
08/04/2011:  Fix note, DF005 relay now confirmed as substitute.

  © copyright, 2011, R. Fleischer