Topic: 1975 CB360T start & idle problem

[HammerSchlagen]

Good Afternoon,

I recently purchased a 1975 CB360T, overall in decent shape. It fired up from cold and I test rode before purchase, took some messing around with choke to get it to idle.
I'm having trouble getting the bike to idle and it's been dying once it gets hot, I have to keep constantly on throttle to keep it alive. But before I even address that.

Seller put new battery in the bike, this model.
 https://www.amazon.com/POWERSTAR-12N9-4B-1-Motorcycle-Battery-Replaces/dp/B00XNK8Y52,

I put the multimeter to it and it is only at 4V. This could be because I kept using the electric starter but regardless I need to charge it. Can I use my portable car charger to charge this battery?

https://www.amazon.com/NOCO-GB20-UltraSafe-Lithium-Gasoline/dp/B015TKPT1A

Let's say that charger is safe and I charge up to 12.6+V, if the idle problem persists where would you recommend I begin my troubleshooting?

Thank You

[HammerSchlagen]

Normally I understand this would indicate the battery has reached the end of it's lifespan, but this is a brand new battery. Could I have just drained it from the electric start?

[low-side]

The electric start should have stopped working long before the battery got that low.  You likely have a parasitic drain somewhere.