Boxerworks.com

Gidday,

So a couple of months back I removed the starter motor from my 1978 R100RS for general maintenance reasons as it was right there while I had the top cover and everything else removed around it, plus it was slipping a little on start up and after 37 years it had accumulated as little crud and grime underneath and around it so out it came for a makeover and off to the local auto-electrician it went for a new Bosch drive gear..

So two months down the track the mild restoration of the bike is nearer completion, its only done a few km out on the road for testing reason and only being started up on the bike lift for tuning purposes, but yesterday when we went to start it and bed/seat in the rings after having installed new nikasil barrels, pistons and rings etc, after a few cranks the starter was only just engaging, it turned over the engine for a little but was losing and lost power like the battery was low on power and could not turn over the engine in the end or this morning again... Buggar!!

Today I removed the engine cover and discovered this, see pictures!!







Any ideas as to why a rebuilt starter motor with a fully charged new AGM battery would not turn over the engine as I am not knowledgeable with starter motors but this just seems to be a strong cover/shield of some sort that is broken and it was still just sitting in its correct position, but cracked in half when I found and removed it from the bike today.

I have never seen the starters on my bikes, but I would have to guess that lose piece was shifting enough to allow rubbage inside that would lead to rapid decline in performance.

Snowbum discusses issues with starter installations and swapping from Bosch to Valeo, etc. I haven't been in there very much myself, but it appears that the fit is critical and care must be taken to ensure that the nose area doesn't get damaged or twisted such that it can crack. It's a cover of sorts and I suppose it must be critical for some reason...maybe just to keep dirt/grime out.

Kurt in S.A.

Is it possible for the gear axle (armature?) to move too far forward, due to wear of some part(s), causing the gear shaft to hit the end of the bell housing?

I've never taken one apart, myself, so I really don't know what I am talking about.
Call it "Rob's Logic", and be forewarned.

I have moved them from one engine to another with no issues, but they were all early R65 engines. Don't know what came on those.

Regarding the second photo within your trilogy of starter sadness... Is that rust on a portion of the broken nose piece? Could there have been an existing crack -the rusted area- that finally failed the part?

Monte

That nose supports the end of the armature when the bendix is engaged cranking the engine. The gear when it's thrown out by the solenoid should bottom against that collar just in front. Is the solenoid throwing the bendix out too far?? IIRC that gear should float on the end of the shaft, with it's forward movement controlled by the solenoid, knocked backwards when the motor starts. I find it hard to believe that the solenoid was throwing that gear out so hard it broke the end of the housing off. It sure looks that way though. Armature position inside the housing may be part of the problem, if it is too far forward, then it throws too far out against the housing. Check to see where the yoke from the solenoid is engaging the bendix, if it is mis-positioned and behind the groove it should be in it will send it too far forward, possibly breaking the nose off, like that.

I've never seen that on an Airhead.

On the automotive side that happens when the timing gears (chain/belt) are worn out or the ignition is severly out of time, causing the engine to kick back when the starter is engaged. It happens often and is not covered by the starter manufactures' warranty.

Gidday,

Thanks for the info fellas.....

I have sourced a replaced used nose cone locally, the internals of the unit where refurbished only a few months back so if the nose cone is replaced the unit itself would be still usable with what you can see in the picture is what I am trying to say or has the gear worn to much on the end??

Grant, did the autoelec replace the starter drive? That's what took weeks to get wasn't it?

Here's a picture with a new one on the left (made in Brasil from EME) and my old one oem (made in Espana )showing wear.


The teeth look ok (?new) in the picture of your broken starter below, but the perimeter around the gear looks damaged. Under the 401 numbering and a little at 3 o'clock. Why would that be damaged if it was a new unit? It doesn't look clean enough to be new, and the chipped damage is suspicious.


Were there any metal chips on the floor of the starter area.

The rust suggests the crack was pre existing.

Gidday,

No damage there Steve, I just went out and had a look mate after reading your post and it was a light coloured grey grease around the edge wiped it off and all is like new