750SF3 location of Reg and start relay

Skeeta

Skeeta

Junior member
Location
Coolum Beach, QLD
Gday,
Rebuilding a 750 SF3 (1976), all in bits, trying to work out wiring lay out, any photos out there of location of Regulator and Start relay attachment locations and the rest of the speghetti(I have a wiring diagram 750SF2)
Thanks
Skeeta
 
Starter relay is left of the battery box with the fuses.
Regulator is on a rubber strap across two top frame tubes to the rear of the tank.

Paul
 
Paul Marx said:
Starter relay is left of the battery box with the fuses.
Click to expand...

On the basis that 'A Picture is Worth a Thousand Words'  ...  ;)

Courtesy of the Green Book, btw.

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I would advise not using the original starter relay, it's 42 years old.  Mine stayed on and destroyed the starter motor. A Bosch BMW K100 relay has the same hole spacing. I also fitted an electronic regulator from www.dynamoregulators.com
 
Nat Magee said:
I would advise not using the original starter relay <snip>
Click to expand...

Good advice.  The Bosch part number for the replacement is 0 332 002 161 or 0 332 002 160.

There is slight difference between the two which, in practice, probably makes no difference.  But for completeness sake here it is, as explained here by Piet:

"Several Beemer Flying Brick models used the same Bosch relay as Laverda, just a later version with a plastic housing.  But it is actually not just a simple 75A relay.

Model 0 332 002 161 has an internal resistor/diode thingy to prevent electrical peaks entering the electrical system during or immediately after the cranking process.  The starters can draw 250A and more while cranking, and if that shoots into the loom, something can/will blow.

Very few relays have such a precautionary device.  Most other bikes use smaller starters with far lower draw, making such a measure unnecessary.  Will probably be quite OK to use a simple relay on a bike running on points ignition, but most electronics are far more sensitive to high voltages."

Update:
(Wonders of the Internet 'n all that ...) Here's evidence of the above, found on Bosch's own website.  Note that only 161 is described a 'starter relay'.

luomSL_h!K.jpg

 
I have stopped using the plastic cased Bosch starter relays.
I had 2 fail almost immediately in that the contacts welded themselves closed during starting which meant the starter was turning non-stop.
I had to rapidly disconnect the battery.
On prising off the plastic housing and saw that not only were the contacts welded together, the surface area of the contacts was less than half that of the original metal-clad relay.
First one failed, fitted second one, and that failed in rapid order too.

I took them back to the supplier, who had to send them back to Bosch and after investigation by them I got my money back.

These relays are marked in the Bosch parts book as replacements for the metal-clad ones, but they are not up to the job in my hard-won experience.
 
Interesting, Grant (and a bit heart-stopping for you, I dare say! :o).  First time I've heard that.  I'm using a 161 relay in my Corsa at the mo'.  So far, so good.  But who knows for the future ...?

Not sure I'll reinstall the old one quite yet, tho' ...  Dunno.
 
As Grant warns, the current Bosch production of plastic case starter relays is not of the same quality as the original 'Made in Germany' OE fit. The earlier metal cased relay is generally more reliable and its cover can be removed and the (larger) contacts cleaned up with very fine emery.

I gave up on both and fitted a Japanese starter relay rated at 150 amps. Pulls in with a solid thunk instead of a light click. Believe it is OE for Aprilia RSV1000 and similar - part no AP8112927.  Bit of a squeeze to clear the tool tray on an RGS (I cut off the relay's metal wiring support bracket) and a new mounting bracket is required.
 

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Here's a Kawasaki starter relay on my Jota - has been perfectly reliable over many years (and yes the trigger earth wire has been tidied up since I first fitted it  :) ).  The horseshoe shaped bracket was homemade from simple strip Alu.

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