Starter ripping its' pants

[tunnelrider]

Hi everyone out there,
Been having a great stretch of trouble free riding but...  as you get on old bikes... something that needs attu pops up regularly.
Recently on cold start up my Bosch starter is turning the engine over fine 'till the engine starts catching (1-2 secs) then a loud screeching starts matching the catching 'till the engine's running (1-2 sec). I'm thinking the starter needs inspection but wondering if anyone's come across this before and can kindly inform me a bit before I start taking it apart?  Have I missed lubricating something on the starter? When the engine's warm it doesn't have the problem.
Thought I'd ask you good folk here before I start trawling through Snowbum's amazing pages.
Cheers

[wilcom]

then a loud screeching starts matching the catching 'till the engine's running (1-2 sec).

Sounds like the Bendix is not retracting after starting. Could be a metallic failure issue and it could just be a dirty sticky shaft.

I'd be leaning to dirt and sticky. It does need to be addressed soon as the condition could get violent. Have heard of starter noses being damaged if left uncorrected.

[Tony Smith]

Agree with you Wilcom, might be a couple of things, but a clean and regrease is almost guaranteed to fix it.

[BPT]

I've seen some write ups about removing it completely tearing it down but is there any kind of cleaning or greasing to do with it still in the bike?

[Tony Smith]

I've seen some write ups about removing it completely tearing it down but is there any kind of cleaning or greasing to do with it still in the bike?

Sadly - No.

Starter motors lead long and trouble free lives, all they ask is bushes, lubrication and brushes.

It is unlikely that any BMW motorcycle will ever "wear out" a Bosch starter motors - they are a bit "over-engineered". The most common (by far) are (in order) -

lubrication failure on the bushes and bendix due to crud ingestion.

Motor brushes stuck (by crud ingestion)

Motor brushes worn down (have seen this exactly once)

Failure of pull-in solenoid (seen twice)

Weird stuff like winding failure (once)


So..... Pull it out, disassemble, clean to within an inch of its life, reassemble using either the special grease known only to auto electricians or using waterproof boat trailer bearing grease, and it will go another 40 years without complaint.


By all means change the brushes if you really think you need to, but be aware that you need a pretty powerful soldering iron and a high lead content, flux free solder . A long time ago I put new brushes in using "electronics" solder and the amount of current that passes through a starter created enough heat to melt the solder I'd used and defeat my good work - this was however on a VW car which uses a very similar starter motor.


Lastly, there are Valeo and even Nippondenso starters that will bolt in. Hundreds of thousands of words have been written about Valeo starters. Nippon denso make a fine starter, apparently the one needed is very common and only needs 20 minutes work with a No.1 bastard cut file to "adjust" the fit into the boxer engine. But why would you bother? Refurbing the Bosch will take a few hours of your time and it will then soldier on, working perfectly well beyond your likely tenure as the motorcycle's carer.

[Bob_Roller]

I have lubed all three starters on the R65 and the Guzzi, all use the same starter .
Not a difficult job .
There used to be a write up I think in the FAQ section about Bosch starter refurbishment .
It's on the second page of the FAQ section, first thread .

[BPT]

I'm not having any particular problems with it but will be messing around in that area next week.  I was wondering if there was anything I could hit with some oil or grease while I had the cover off.

If not, I guess I'll just plan to pull it out and try the full Refurb somewhere down the line.

[wilcom]

Brook Reams has a Britannica Encyclopedia quality write up on the Bosch starter

https://brook.reams.me/bmw-motorcyle-rebuilds/1977-bmw-r100rs-rebuild-project-index/12-bmw-r100rs-refurbish-starter-motor/

[tunnelrider]

Thanks for your info and links Wilcom, Tony, Bob and BPT. I'll take a look at them before I take the starter out, take it apart and take some photos. Got the Clymer for a schematic.  I've read here before the engine case often needs a bit of touching up to fit the starter back in properly so will be aware of that.
 
Bob, what did you use as a lube for the starters you've done?  Tony you mention waterproof boat trailer grease.  I've got a tube of waterproof lithium grease in the garage that I use for things like the throttle twist grip linkage, lever pivot bushings and bolt threads, it's white. Will that do?  Guess it needs a grease able to stay on in the heat up/cool down of the engine.

[wilcom]

I've read here before the engine case often needs a bit of touching up to fit the starter back in properly so will be aware of that.

Don't be too quick to "touch up" the case. I changed from a Bosch to a Valeo and the bolts now came in from the other direction. I had a problem getting a socket on the bolt head and promptly reached for the grinder. With the proper wobble socket, I think the job could have been accomplished.

I sometimes have more "I WANT IT NOW" than is good for me or the bike.

[Bob_Roller]

If I remember correctly, it was recommended that you use a high drip point, high melting point grease and also that it  be a non-conductive grease .
I work for an airline and when consumable items, like grease, oil, sealants and adhesives have reached their shelf life, they are discarded .
The company has no problem if you take these items home for your own use .
I'm using items that are not available at the retail level, industrial use only .

[Bob_Roller]

A side effect of an old starter with dried up lubricants, can be hard starting .
I developed a cold, first start of the day problem in cooler temperatures .
The starter draws more power to operate when  it's dry on lubrication .
Bikes with factory electronic ignition systems, don't work very well, if at all, below the 9-10 vdc region .
Disassembled the starter cleaned and lubed it and the hard starting issue got a lot better, also found an ignition coil was faulty, primary coil had about .7 ohms, should be 1.5 ohms .

[tunnelrider]

use a high drip point, high melting point grease and also that it  be a non-conductive grease .

Roger that, thanks Bob. Without looking yet I don't think my lithium grease will cut it, it's too light.

Refurbing the Bosch will take a few hours of your time and it will then soldier on, working perfectly well beyond your likely tenure as the motorcycle's carer.

Ahh Tony, if only everything was as simple as your romantic prose 

Now, to find a spare few hours to do it...
Thanks everyone.

[tunnelrider]

Well, thanks to all your advice - it's not a hard job to take apart, clean and lube the starter.  Unfortunately it hasn't really fixed the screeching problem when the engine starts catching, although it has reduced it's severity.  I think the problem lies in the round ratchet device attached to the starter gear that spins the clutch carrier/flywheel.  I'm thinking it's either dry inside or worn out. 
 
I guess the ratchet device on that driven gear must exist so when the engine catches and makes the flywheel spin faster than the starter motor the small starter gear can spin freely then engage again if the engine hasn't fully caught.  And I'm presuming this is why it's making the screeching noise when it starts catching.  It's no good - makes a start embarrassingly noisy and might eventually fail.

I'd thought it might be the cause after I took the starter apart and inspected the different pieces, the driven gear was able to turned one way while holding the armature but it was pretty stiff to turn (not meaning the helical gear up/down movement).  So I placed the piece vertically and filled the ratchet top surface with light oil in the hope it would wick down into the ratchet.  It freed up a little but most of the oil drained down the centre shaft of the armature to the helical splines.  Perhaps more time in a vertical position with more oil or a thinner lube like CRC556 on top of the ratchet would help.  Wouldn't be too annoyed about pulling it out and apart again.  But I've got the luxury of a spare motor with a starter motor, might put that on.  Why didn't I just do that to start with you ask? Good question...

Other things that might interest some - it is possible to get the left mounting nut on and off using a 1/4" wobble bar without grinding away any of the transmission case, but I'm going to grind some off next time anyway, as it's a bit annoying not having a proper feel of how tight you are tightening the nut on re-install. The socket doesn't fully fit over the nut and will eventually slip, albeit might be tight enough.

Also my 1985 R65 had no starter motor plastic nose cone cover - does anyone know if BMW stopped putting the plastic nose cone covers on at some stage?  The 1980 spare engine does.  I put it on while re-installing the starter, it definitely fits.   What makes me think the 1985 never had the plastic cover is that the nuts were nylock, had no recess for the cover retaining wire like the other nuts and perhaps the starter's never been opened before, one of the few jobs on this bike I din't see any PO work.  The brushes could've been replaced, being 13.8mm length, but looked like a factory press of the the brush pigtails to the holder, definitely not a home solder, so they're probably the originals...

It may've been take off at some stage of course and got missed putting back on. D:)

[georgesgiralt]

Hello
My 1982 has not got the starter motor nose cover, even if the fiche for my serial shows it.