I'm hoping some gurus here can point me in the right direction. What I would like is a switch on my dash that is REQUIRED to be on in order to start the bike. Once the bike is running (some period of time) if this switch is not turned off, I want the bike to turn off (break the circuit, etc). I know I can do this by programming a microcontroller with a relay and programming it... but don't want to rely on that in the middle of the bush somewhere. Is there a practical, non-computer solution to this? Are there physical switches, etc that have inherent timers, etc or any solution someone might see to this?

 

Welcome to AAC!
We're not psychic. Can you post a complete wiring diagram for your bike?

 

It's an '84 CB450SC - I can post a diagram, but doubt very much it's accurate at all. This beast has been rewired a number of times. Ideally the solution just needs to interrupt a circuit (main or ignition coil, etc) but I have no idea if parts that do something like this exist or if this would always be done with something more complicated like a microcontroller, etc.

 

What "period of time"?
A 555 timer one-shot with a transistor driver and a relay would likely do what you want if the time is no more than a couple minutes.

 

Time period is anything more than 5-10 seconds (enough time to flip the switch again) and ideally not longer than a minute or two. The goal is some slight theft deterrence, should someone want to drive off with her and knows how to bypass the ignition switch itself. if they keep starting the bike and then it cuts off, hopefully they just leave it and move onto another bike to steal.....

 

Pity the image isn't sharper. I can just about make out a capacitor discharge ignition unit. Interrupting the ground line to that might meet your needs.

 

Thanks for all the input already! I suppose I really should have been more clear and been ready with diagrams, etc. Thanks for everyone's patience - I've drawn something simple to clarify, see attached:

My hopes are that at point "A" there would be a toggle switch. This switch would need to be "ON" in order to engage the starter motor. At point "B", effectively just a break in the main circuit to ground, something here would react to the switch at "A" being left on for more than let's say about a minute and would break the circuit but otherwise keep the circuit complete.

I don't know if there is a way of connecting these points to communicate in this fashion without the use of a programmed microcontroller.

Again, thanks so much for the input already, great community to stumble across!

 

I'm not familiar with your bike's electrics, but I would expect breaking the main circuit or the starter circuit would involve switching much higher current than breaking the ignition supply circuit. Switching high currents is generally something to be avoided if possible. Your call, of course.

 

Here's my take on a circuit using a 555 timer that should do what you want.
The LTspice simulation is below.

After the Ign switch is turned on, flipping the SPDT switch (simulated by U4, blue trace) triggers the 555 ON and starts the timeout.
This activates relay U5 (can be automotive type) which turns on the Ign(ition) (red trace) output and allows the vehicle to be started.

If the switch is not opened before 24 seconds, the 555 times out (yellow trace) and Ignition is turned off (shown at the 29s point), stopping the engine.
(The 555 timeout is about 24 seconds as determined by the value of R2 and C1.)

If the U4 switch is closed and then opened before 24 seconds (shown at the 70s point) then the NC switch contact prevents the 555 from timing out and the Ignition stays on.

If you want a longer timeout, you can increase the value of R2 and/or C1.

 

Okay, here's an alternate circuit using CD4011 NAND gates configured as an RS latch.
The LTspice simulation shows a lockout delay (determined by R1 and C1) of about 3 seconds.
Thinking about it, you don't need much delay since normally you would just rapidly turn the switch on and off to keep the Ignition output latch on.
Thus the engine will not start unless you turn the switch on and off within 3 seconds.

If you want the delay long enough to allow an engine start and then have it stop if you don't turn the switch back off, increase the value of R1 and/or C1.