Question on ignition switch wiring for chopper

[Resto_Paul]

So after getting stuck and having to bypass my 2 position ignition switch last week I've been thinking about my electrical system and think I have a flaw.
The 2 position key switch I have is only rated at 4amps at 125V. I made the poor assumption that at only 12V it could handle more and I have all of the power going from my battery through the switch and to my 3 circuits (dual headlights, led tail/brake, electronic ignition). Im guessing this is too much for the switch? I'm limited on switch options as I need one that the key can be removed in the on position as well as off.
If i run a 4 pin relay rated at 40 or 50 amps with the switch pulling 12v from battery and acting as my positive trigger this should take all the load off the switch correct?

 

[Signal]

Yes that will work. You might want to put a fuse in the line from the battery. Also check the DC rating of the relay. You will need to feed the relay control circuit from the battery not from the load side of the relay.

Contact rating is different for AC and DC. It is much lower for DC as the switch contacts take a beating due to DC current wanting to continue to keep flowing causing arcing at the contacts. This is exacerbated by DC switching of inductive loads think how ignition coils work.

With AC it is also not straight forward as AC rating is different for different types of duty, and contactors are derated when switching plugging loads like large motors starting and stopping repeatedly. They have a higher rating for resistive loads.

 

[Its been a long time]

Using a relay to put the best voltage possible onto the ignition system is a very good idea. For the best sparks you need the best voltage the battery can supply. I wired the electronic ignition and coil on my 650D through a relay. Recommend a 10a fuse upstream of the relay to protect the wiring.

 

[Resto_Paul]

Using a relay to put the best voltage possible onto the ignition system is a very good idea. For the best sparks you need the best voltage the battery can supply. I wired the electronic ignition and coil on my 650D through a relay. Recommend a 10a fuse upstream of the relay to protect the wiring.

The relay is going to trigger the power to everything now not just the ignition circuit. Is a 10amp fuse adequate? I thought I'd need something slightly lower than the relay rating like a 40 amp? I purchased a 50amp relay from Racetronix that's coming today. Besides the ignition it's only powering dual headlights and an led tail.

 

[Its been a long time]

The relay is going to trigger the power to everything now not just the ignition circuit. Is a 10amp fuse adequate? I thought I'd need something slightly lower than the relay rating like a 40 amp? I purchased a 50amp relay from Racetronix that's coming today. Besides the ignition it's only powering dual headlights and an led tail.

10a is fine for ignition system protection. My 1977 650D has a single 20a fuse protecting all circuits. Later bikes had multiple fuses. 10a is indeed a bit low to power an entire bike's electrics. 10a is a ~120w load.

 

[Resto_Paul]

10a is fine for ignition system protection. My 1977 650D has a single 20a fuse protecting all circuits. Later bikes had multiple fuses. 10a is indeed a bit low to power an entire bike's electrics. 10a is a ~120w load.

Ok so to power it all what amp protection fuse do you suggest....20? My electrical knowledge is limited to 1 class I took in high school haha

 

[Its been a long time]

Ok so to power it all what amp protection fuse do you suggest....20? My electrical knowledge is limited to 1 class I took in high school haha

I hesitate because I don't know your bike. A standard bike has a 20a fuse protecting all circuits. Following what the factory did is probably not a bad idea.

 

[Resto_Paul]

I hesitate because I don't know your bike. A standard bike has a 20a fuse protecting all circuits. Following what the factory did is probably not a bad idea.

Understandable. I'm running way less than factory. I think my only error is on the switch. Beyond that I have power right now going from the switch to 3 seperate circuits all on auto resetting breakers. Dual 35w headlights on one, the led tail/brake on one, and electronic ignition on the last. No other electric at all on the bike. Just not sure if it's fully understand how the potential 20 amp fuse from the battery to the relay is adequate enough but again my knowledge on the subject is limited.

 

[Its been a long time]

Understandable. I'm running way less than factory. I think my only error is on the switch. Beyond that I have power right now going from the switch to 3 seperate circuits all on auto resetting breakers. Dual 35w headlights on one, the led tail/brake on one, and electronic ignition on the last. No other electric at all on the bike. Just not sure if it's fully understand how the potential 20 amp fuse from the battery to the relay is adequate enough but again my knowledge on the subject is limited.

OK. A 20a fuse carries up to a 240w load. That's volts x amps = watts. You're not going to get near that, I doubt. And that's the main fuse rating Yamaha used. At the end of the day you're aiming to prevent a fault setting fire to the wiring. Provided your wiring can take a 240w load and not burst into flames, then a 20a fuse as used by Yamaha looks like a good bet to me.

 

[Resto_Paul]

OK. A 20a fuse carries up to a 240w load. That's volts x amps = watts. You're not going to get near that, I doubt. And that's the main fuse rating Yamaha used. At the end of the day you're aiming to prevent a fault setting fire to the wiring. Provided your wiring can take a 240w load and not burst into flames, then a 20a fuse as used by Yamaha looks like a good bet to me.

Thanks I appreciate the input. I'll be adding a larger gauge wire from the battery to relay with the fuse so it should hold that load. Like I said the rest are all seperate legs with their own breakers so they're protected.

 

[Its been a long time]

Thanks I appreciate the input. I'll be adding a larger gauge wire from the battery to relay with the fuse so it should hold that load. Like I said the rest are all seperate legs with their own breakers so they're protected.

Sounds like a good plan.

 

[Resto_Paul]

Wired in a 50 amp Racetronix relay today to run all power through and fused it with a 30amp fuse.