engine stop relay 1978 900GTS

byme22 · Post by **byme22** » Thu Oct 15, 2009 1:06 pm

Hi my name is Danny Davis I'm located in Seminole Florida USA.I have a 1978 900 GTS and a 1973 BMW 750/5 toaster tank.I need a stop engine relay for the Ducati.The last owner had a problem and bypassed it.You now have to stall the bike out to stop the engine even when the ignition is turned off.Any one got any ideas.Thanks in advance,Danny

Lumpy · Post by **Lumpy** » Fri Oct 16, 2009 5:36 am

Hi Danny. My engine stop relay packed it in some 20 years ago. They often do as i understand it and are part of the rich tapestry of 70`s Ducati electrics. My point being is that at the place I was working at the time there was an electrician who was also a bike nut and he threw together a solid state unit that is still on the bike today and has`nt given an ounce of trouble. It looks a simple enough thing he build with a couple of round...............eleectic thingo`s. You know......capacitor resistor looking things he stuck to a bakealight plate.
What I was about to suggest is if you took the old engine stop relay (if you have it, or even just a wiring diagram) and a wiring diagram to an auto electrician he may be able to sling one together for you. It took this guy about half an hour to build and he built it from stuff he had laying around and he was`nt all that Ducati familiar.
Personally i would`nt go back to the standard unit as all aquaintances with Ducati`s I know had issues with these things.

byme22 · Post by **byme22** » Fri Oct 16, 2009 6:27 am

Thanks for the reply.I looked at the relay on the bike and it is a japanese one that looked like it had been modified.I do have a wiring diagram.i will check with an electrician to see what they say.I'm surprised nobody makes a modified one that works well.Thanks for the quick reply,Danny

wdietz186 · Post by **wdietz186** » Fri Oct 16, 2009 1:52 pm

Danny, Do you have Bosch ignition? Or do you have the Ducati setup with the red boxes/ign. coils? If you have Bosch ign. the power to the coils is run through the kill switch and it should turn off when the ign. or kill sw. is turned off.If you have the Ducati ign. with the red coils the stop device simply grounds the coils.When working normally the relay is open with the ign. sw on. Turning the power off closes the relay and grounds the wires to the coils. Look at the 77 SS wiring diagram and you will see what I am trying to explain.It could be difficult to find a relay that is normally closed when not energized as most automotive relays are normally open when not energized. hope this helps,Bill

byme22 · Post by **byme22** » Fri Oct 16, 2009 2:08 pm

I think it has the Ducati ignition.The person i bought it from had a problem with it.He disconnected the green wires to the coils.At the moment the bike does not turn off with the ignition key.It can be started without the key.I will try and get the ignition switch modified and do away with the kill switch.I just like a bike to be as original as possible so I was going to try and replace the relay.thanks,Danny

Lumpy · Post by **Lumpy** » Sun Oct 18, 2009 5:49 am

Not too sure but i think it`s a little more involved than just grounding the transducers. The classic symptom of the engine stop relay failure was running on one cylinder. Unless the relay was twin contacts to handle the current flow. Electrickery is not my strongest subject. If grounding the transducers pure and simple is how they shut down maybe grab a kill switch, they are cheap as chips from dirt bike shops and very easy to install. Also can be easily removed if originality is a concern.