Purpose of electric start safety interlock

[Dazza]

Of course I know what it's for ..I just don't see the point of it...you have a switch on the clutch lever that when pressed goes ground, this then goes to the interlock behind the horn casing and then onto he relay, the interlock has from what I can see a 12v supply to it and the switched negative from the clutch lever just passes through it, if taken out of the circuit and the wire from the clutch switch is joined straight through to the relay - it still works exactly the same way..

Any ideas - assuming the above makes sense to anyone else other than me?

[johnny LIS150]

its standard on most bikes and scoots with leccy start these days .
It forces you to pull the clutch in in order to power the starter motor so that there is no possibility of you starting the bike/scoot in gear.
Imagine the carnage you could cause starting in gear with full throttle in a crowded public place !

Yes you can simply join the wires together at the relay and remove the relay and safety switch

[Jack221]

Makes perfect sense......Its all about current ratings and long term reliability

[Dazza]

its standard on most bikes and scoots with leccy start these days .
It forces you to pull the clutch in in order to power the starter motor so that there is no possibility of you starting the bike/scoot in gear.
Imagine the carnage you could cause starting in gear with full throttle in a crowded public place !

Yes you can simply join the wires together at the relay and remove the relay and safety switch

I understand fully about the clutch lever needed to be pulled in and the consequences of this not being in place....

What I asked was what the purpose of the interlock unit that's fitted behind the horn casing, I don't see the need for this when you could bypass it altogether with the clutch switch wire going directly to the relay with no issue...so why is it fitted?

[johnny LIS150]

sorry I misunderstood your question

The purpose of having the relay is to isolate the power supply feed to the starter motor circuit from your starter switch otherwise you would be running the heavy power load for the starter motor through the small starter switch and its associated low current cable

These diagrams may help illustrate the principle of how relays work and why we use them for this sort of application https://www.google.co.uk/search?q=start ... B350%3B241

[Dazza]

No problem,

I also understand what the relay is for , the interlock unit is separate to this, it sits behind the horncasing - a little red box, one wire from the clutch switch goes to it then comes out to the relay behind the battery , here are two other wires - a negative and I presume a +12 v positive from somewhere - it's this item that I don't understand what is for or how it works,

[Jack221]

Its just about the reliability

[johnny LIS150]

No problem,

I also understand what the relay is for , the interlock unit is separate to this, it sits behind the horncasing - a little red box, one wire from the clutch switch goes to it then comes out to the relay behind the battery , here are two other wires - a negative and I presume a +12 v positive from somewhere - it's this item that I don't understand what is for or how it works,

if you tell us the model and year of your scoot and perhaps show us an image of the part in question we might be able to help further.
As far as I am aware an interlock is a relay ?

On modern bikes and scoots the 12v supply is usually run through a series of switches and relays so that several things have to be satisfied before power is fed through to the starter motor when you press the starter button. The 12v+ and earth for the starter motor is never run directly through the starter button or the clutch switch it must always be isolated even if it doesn't go through a relay it must be fused at a higher rating and have cables that will safely cary the current

On my bike for instance the bike has to be off the stand, the clutch has to be pulled in and the gears have to be in neutral and the ignition on before the starter is fed with power

[firekdp]

It's the "PRD" relay, it's sole purpose is to make sure the starter circuit is inoperable when the engine is already running.

[johnny LIS150]

ok ........so it receives a feed from the stator when the engine is turned over by kickstart or starter motor. It can be disconnected and the interconnect can be bypassed if desired. Just have to hope that you don't inadvertently press the starter button when the engine is running