I don't see any problem with doing what you suggested, should work and be as safe as the system it has now if not better.
If you tap into the ignition circuit blk/wht wire and use it to trigger a relay to operate the shut off valve and pump it would shut off in the event of a tip over.With the limited comments I have received so far, I'm studying the bikes wiring schematics to see what are my best options for bypassing the engine control module. I do want to include the bank angle sensor for safety reasons.
Bill - N5HQ
While you are at it install a relay or just use the same relay for the pump and fuel valve and power the blk/wt wire going to the coils. That has been the cure for lots of 1500s with starting problems.Nope, wouldn't do any good because the vacuum controlled fuel shut off valve would not open unless the engine was cranking. No cranking = no vacuum. No vacuum = no fuel.
I'm pretty sure what I'm going to do now. I'm going to put in a power distribution block and power it from the battery and re-wire everything electrical that I have added over the years. Anything needing to turn off with the ignition switch will get a relay. This way I can have separate fuses for everything instead of piggybacking off the existing wiring. Should have done that years ago. I have the plastic off now and I can see everywhere where I fished wires through and I want to clean all that up. Good winter project.
Thanks everyone for all the suggestions.
Bill - N5HQ
Bypassing the ECM to power the coils directly frees up power to the ECM so it actually gets more voltage.Make sure that if you do the "relay bypass" mod that you do the relay wiring to INCLUDE power to the ECM from the relay, not bypass it.. It's low voltage at the ECM that causes a no spark condition, supplying direct voltage to the coils alone will not help the ECM to trigger them. In fact, if you feed direct power from the relay to the ECM alone, it will fire the coils, even if the coils are not on direct power from the battery.
It should still shut off if the BAS is tripped.Only thing that concerns me about that setup is if you happen to tip it over, you'll continue to pump fuel into tipped over carbs and besides the fire risk you stand a good chance of hydrolocking the engine.
I'd give the fuel pump and electric valve a separate relay triggered by the line which used to drive the fuel pump directly. This would come from the ECM on a '90 to '00 wing, not sure on an '89. That way if you tip over the pump will stop and valve close.