wiring Dilema

[r75bitsa]

G`day
Will put it in here this time.

Getting to the final stages of a ground up on a `73 LWB R/75. Few things changed, r100 motor, headlight, wiring loom, 4 speed with r100 diff r100 tank and seat. Had a few issues with the wiring loom (who doesn`t) after a tidy up, getting rid of buzzer relays and associated wiring I have the following:

Headlight, indicators, tailight foot brake work as they should, have noticed a notchy sensation when turning the key to the on position, When backed off a bees dick the headlight stops flickering and the indicators work. When connected to the battery the park light/taillight come on straightaway without the key being operated. Both the starter/headlight relays are aftermarket, have the relevant pins and numbers and other than the park/tailight head scratcher seem to be doing the job.

I still have the starter/carbs and a digital speedo/tacho left to go so Iam wondering whether the ignition switch is shagged or if I may have a relay mismatch.

Regards to everyone, top site.

[SteveD]

Willkommen!

Is the wiring loom from the 75 or from the 100?

I'm wondering if the relays were different? Maybe worth a check.via the MaxBMW fiche ..
http://www.maxbmwmotorcycles.com/fiche/PartsFiche.aspx

[r75bitsa]

Wiring loom is from a circa `77-78 r100, had to remove the voltmeter/clock wiring etc, the relays are from Supercheap
(yeah right) all pins required are present with relevant #`. They seem to be doing their job as in they work its just when the battery is connected to the starter relay the park light is on straightaway. The ignition switch needs to be backed off a bit before the headlight stops flickering so I`m wondering whether its a combination or just the switch

Thanks

[SteveD]

Relays from SCA doesn't fill me with confidence despite the similarities.
Headlight relay



Starter relay


Flasher relay

[Ken in Oklahoma]

Headlight, indicators, tailight foot brake work as they should, have noticed a notchy sensation when turning the key to the on position, When backed off a bees dick the headlight stops flickering and the indicators work. When connected to the battery the park light/taillight come on straightaway without the key being operated. Both the starter/headlight relays are aftermarket, have the relevant pins and numbers and other than the park/tailight head scratcher seem to be doing the job.

Indeed, welcome to the forum.

I would start by replacing the ignition switch. Backing the key off a bees dick shouldn't give you the flickering and sudden activation of a circuit, no matter what wiring errors may exist. That's a tough prescription, I know, cuz those switches aren't cheap. Also the park light/tailight shouldn't come on at all without the key being turned on. That could be a wiring error, but a strange acting ignition switch has to be a suspect.

It would be a pain in the ass, but you could work out the ignition switch logic in terms of which wire gets connected to which in what position, and manually connect the wires. At least one of the Airhead coloring books has a diagram with that information. I'm thinking Clymers, especially the big black book. If you can't get the flicker and you can't get the park light/tailight to come on when it shouldn't, that would strongly suggest the ignition switch.

An aftermarket automotive ignition switch could be made to work, but the stock switch location on the L/H headlight ear wouldn't work out, and you would have to work out your own switching logic. With all the wiring in the headlight shell, the idea would likely be impractical.

You are a brave man r75bitsa.

Ken

[r75bitsa]

More like puzzled mate, got a few ideas, but at the moment Iam going to walk away before I drop
the headlight or dent the tank, you know what I mean, probably been there yourself.

Regards and thanks.

[r75bitsa]

Just had one of those eureka/dickhead moments, when I purchased the starter relay in its shiny packaging
I thought that I could see all of the required pin #`s. Pulled the starter relay off had a real close look and I find
that what I thought was 87a was in fact 87 with a dob of plastic beside it so I have two 87 pins, which I have been told is like a straight hook up of battery power, fingers crossed this is the problem - everything works just that it works straightaway.

Will keep informed

[SteveD]

Have you got a BMW starter relay? I might have one if they're the same as the later ones.

[r75bitsa]

Haven`t had time to hit the shops mate, if you could have a squiz, if you have a haynes it is the one for a `78
r100 on page 10.20 it would be very much appreciated. Let us know the damage if you have.

Regards and thank you.

[SteveD]

This one? pn 61311243207