'73 R75/5 Bosch Starter Renewal Questions

[moshe_levy]

All-

Took my Bosch apart today per Greg Bender's helpful instructions. No problem (though I must say my R1150RT's Valeo seems like a plastic playtoy in comparison to this thing!). What a tank! Anyway, two questions I need help with:

1) What is the spec on brush replacement? The manuals are useless and basically say nothing about what original length was, and what length they should be replaced at. I figure the answer is "You're in there anyway" but I have no clue as to their rate of wear. Anybody have some real figures?

2) Bender says to soak everything in degreaser - the windings too?? I don't want to screw this up if I can help it.

OK, as usual, thanks so much.

-MKL
1973 R75/5 Cafe (in process)
1977 R100S
2004 R1150RT

[orbitangel]

All-

... two questions I need help with:

1) What is the spec on brush replacement? The manuals are useless and basically say nothing about what original length was, and what length they should be replaced at. Anybody have some real figures?

2) ... soak everything in degreaser - the windings too??

-MKL
1973 R75/5 Cafe (in process)
1977 R100S
2004 R1150RT

First question:

I looked in my BMW (factory) Shop Manual. There are no specs (wear limits) listed for starter motor brush length.
There is a reference to the commutator which says: "The commutator diameter may not be less than 33mm."
Also, they say to undercut the insulation between the commutator segments by 0.5mm.

Brushes are cheap. Why not buy a set and compare them to the used ones?
If your old ones are OK (let's say, 65% or more remaining), put the new set away for future replacement.

Second question:

"Soak in degreaser?" Perhaps a better way to say it is: "Clean the parts."

There are many different degreasers that folks might use - SOME of them MIGHT be harmful to insulating materials.

Why take a chance?

You could get a big aerosol can of contact cleaner (something likw LPS "Electro 140") and hose everything down, using a bristle brush on the stubborn areas. You don't need to "soak" the parts to get them clean.

Good luck!

[kstoo]

CRC Lectra-Motive spray

http://www.crcindustries.com/auto/content/prod_detail.aspx?PN=05018&S=N

[robsryder]

...Took my Bosch apart today per Greg Bender's helpful instructions...

for those that may be unfamiliar with the reference to Greg Bender...

He has a website for Moto Guzzi enthusiasts -
http://www.thisoldtractor.com/gtbender/loopframe_torque_specifications.htm

The old Guzzi's use the same Bosch starter as was used on the BMW airheads. Greg has a very nicely illustrated procedure for rebuilding the Bosch starter at:
http://www.thisoldtractor.com/gtbender/loopframe_electrical.htm#starter_and_solenoid_repa ir_-bosch-