Relay upgrades for '79 GS850G

[sarathchandars]

That is super helpful, Dave. Clearly what I chose isn't going to work. So I'll be on the lookout for something of that rating. Rest of them seem relatively straightforward.

[dgates1]

Couldn't you just install a normally closed relay to the fuses that you want to turn off? Relay action fed from your starter button.

[sarathchandars]

Thanks Dave. I also received a response from ricks motorsports who make aftermarket start motors and on their dyne, their starter motor measured 0.75kW at 12.9V. Which means the relay would have to be at least 60A. While one can argue that the engine might not require all the power it is better safe than sorry and go for a relay that is beefier than my suggestion above. I thought the data might come in handy for others.

[dgates1]

Thanks Dave. I also received a response from ricks motorsports who make aftermarket start motors and on their dyne, their starter motor measured 0.75kW at 12.9V. Which means the relay would have to be at least 60A. While one can argue that the engine might not require all the power it is better safe than sorry and go for a relay that is beefier than my suggestion above. I thought the data might come in handy for others.

The starter already has a dedicated relay that connects directly to the battery. A new one is available for under $70.

Unless I'm missing the purpose of this relay you want for your starter?? You're just looking to disconnect other loads while pressing the starter button, right?

[Nessism]

The bike already has a starter relay. Don't add another into that circuit. Some people add a relay to feed voltage to the coils. That's, arguably, the only relay that will be beneficial.

[sarathchandars]

I agree.. I'm not adding another circuit for the starter. But planning to add relays for the headlight and horns. I was figuring out the rating for the starter relay to replace the existing one because it is clearly old and the terminals are rusting.

[pdqford]

But planning to add relays for the headlight and horns.

The whole electrical system is fused at 15 amps.

The full lighting system is fused at 10 amps.
The "signal" circuit (horns, turn signals) are fused at 10 amps.

That should give you an idea of relay capacity required. for the original system.

Put your meter across your big new horns and measure the resistance.
Divide 15 by that resistance and the result will be the amps draw of those new horns.
Be sure the wire gauge can handle that amount of current for best results.

[sarathchandars]

Thanks Jim, this is super helpful...