Horizons Unlimited - The HUBB

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-   -   Airhead starter brush length (https://www.horizonsunlimited.com/hubb/bmw-tech/airhead-starter-brush-length-98923)

John Roberts 2 Jul 2019 22:48

Airhead starter brush length
 
1982 R100 RS. Neither the official BMW workshop manual nor Haynes give the minimum length. It's the original starter, Bosch with 9 tooth pinion.

Please. :)

Jay_Benson 3 Jul 2019 19:48

have you been in contact with either Motorworks or Motobins?

John Roberts 3 Jul 2019 20:24

Quote:

Originally Posted by Jay_Benson (Post 602023)
have you been in contact with either Motorworks or Motobins?

Motorworks don't know...

Jay_Benson 3 Jul 2019 21:33

I have had a look in the Clymer manual and the alternator brush projection service limit is 8mm (0.32 inch) - they started off at 16mm long. However there is no information for the starter motor brushes. I have some photos of the start motor bushes from the Clymer and the ratio of the width of the bushes to the total depth is 7:3 (that is in the photo the width of the bush is 7mm and the depth - including the backing - is 3mm. I can’t say what the scale is though). There is no indication if this is the worn limit in the text. This would imply that if your bush depth is greater than 50% of the width then it is OK. I could, of course, be talking rubbish.

Jay_Benson 3 Jul 2019 21:58

I have just had a look at Snowbum’s web site for airheads and in the electrical / starter section there is an interesting bit of information that may lead you to get the wear limit where he says the following:

Bosch starters are used in a wide variety of makes & models of vehicles. Sixties & seventies VW's, for one example, use similar starters to the ones in Airheads. 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 parts from www.Euromotoelectrics.com or, Ted Porter, http://beemershop.com.

John Roberts 8 Jul 2019 21:26

Jay, sorry to be so slow in responding to your reply, thank you very much for going to all that trouble. It's strange that the limit on alternator brushes are so readily available compared to that of starters.

I think I'll play safe and get a new set as it's a bugger to dig the starter out from its cosy little nest atop the engine. The only thing that made me hesitate was the amount I've already spent on loads of other stuff while it's having a strip down, it's hard to know where to draw the line between common sense renewals and going over-the-top.

Thanks again. bier

Jay_Benson 8 Jul 2019 22:44

Quote:

Originally Posted by John Roberts (Post 602160)
Jay, sorry to be so slow in responding to your reply, thank you very much for going to all that trouble. It's strange that the limit on alternator brushes are so readily available compared to that of starters.

I think I'll play safe and get a new set as it's a bugger to dig the starter out from its cosy little nest atop the engine. The only thing that made me hesitate was the amount I've already spent on loads of other stuff while it's having a strip down, it's hard to know where to draw the line between common sense renewals and going over-the-top.

Thanks again. bier

Are you on the Airhead list? You can ask a question on there and they get back to you really quickly with expert advice - I will dig outa link in a few minutes - it is an email list and they have to approve you - they let me in so the entry hurdle is set pretty low. It is USA based so you wake up to lots of emails but the content is interesting 75% of the time.

Jay_Benson 8 Jul 2019 22:47

Here you go - http://lists.micapeak.com/mailman/listinfo/airheads

John Roberts 9 Jul 2019 22:22

Jay, no, I hadn't heard of the site before, it does look good. I've just applied to join and a high-level meeting has been convened as we speak to debate the merits of my application. I can sense the rustle of black balls already ... or are they white ...? I've told them I'll sit in the corner and not say very much, I promise ...

Fingers crossed. :unsure:

:biggrin:

Warin 9 Jul 2019 23:20

Quote:

Originally Posted by John Roberts (Post 602160)
I think I'll play safe and get a new set as it's a bugger to dig the starter out from its cosy little nest atop the engine. The only thing that made me hesitate was the amount I've already spent on loads of other stuff while it's having a strip down, it's hard to know where to draw the line between common sense renewals and going over-the-top.

Yep. But look at it this way .. those brushes have been in there how long? 30+years? For the cost of some new ones they too will be good for some 30+ years...

John Roberts 16 Jul 2019 04:36

Quote:

Originally Posted by John Roberts (Post 602196)
Jay, no, I hadn't heard of the site before, it does look good. I've just applied to join and a high-level meeting has been convened as we speak to debate the merits of my application. I can sense the rustle of black balls already ... or are they white ...? I've told them I'll sit in the corner and not say very much, I promise ...

Fingers crossed. :unsure:

:biggrin:

Hi Jay.
Strange, but still no reply to my application, nearly a week now. They must have realised that they really don't want me in their group.

Sigh....

Jay_Benson 17 Jul 2019 19:24

Quote:

Originally Posted by John Roberts (Post 602366)
Hi Jay.
Strange, but still no reply to my application, nearly a week now. They must have realised that they really don't want me in their group.

Sigh....

Would you like me to ask the question and get back to you with the answer? I say “the” answer as when you ask a group of five engineers for their opinion you will get back at least seven contradictory opinions. (I am an engineer and often argue with myself!).

Jay_Benson 17 Jul 2019 19:29

Quote:

Originally Posted by John Roberts (Post 602366)
Hi Jay.
Strange, but still no reply to my application, nearly a week now. They must have realised that they really don't want me in their group.

Sigh....

PM Sent

Jay_Benson 22 Jul 2019 15:24

OK. I asked the question on Airlist and got a heap of replies which in general went along the lines of - "if you are in there anyway get them changed". There was one suggestion that the Bosch starter was a weak link and that if you were able to then changing it to a Valeo starter would be a good move. The actual reply was:

I would not use time and effort for renewing bushes or any parts of the Bosch starter. My R100 /83 has 290,000 kilometers. I renewed the bushes and brushes to get some more grunt for the starter. The Bosch starter was quite marginal from the very first days of the bike and no real advantage was gained.

Three years ago I replaced the Bosch unit with a Valeo purchased from Euro Motoelectrics (BMW VAL-1 with 9 teeth). The difference is HUGE! Now I'm seriously thinking of replacing the 28 Ah battery with a smaller and more easily manageable battery, eg. 22-24 Ah. The Valeo was the best investment on the bike ever, even better than hardened valve seats.

So if you have no purpose to maintain the bike in completely original go for another starter. Note that the assembly is very slightly different from the original. The Valeo is shorter and so does not need the extra supporting bracket.

Warin 22 Jul 2019 23:51

Quote:

Originally Posted by Jay_Benson (Post 602451)
(I am an engineer and often argue with myself!).

There is always more than one solution.


As well as replacing the Bosh with a Valeo there is the Nipondenso... more $ and even less electrical load and weight.


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