1981 cb750 won’t start with new battery

[Tcooper04]

Hi, so I picked up this ‘81 cb750 a couple of days ago in need of a new battery, I replaced the old one with a brand new everstart tx14ah battery. When I first put the new battery in and started the bike, it started up with no problem, I turned it off, & turned it back on a few times, let it sit for like 20 minutes getting my stuff ready to take it around the block, & from then on it won’t start as if I still had the old dead battery in. If somebody could help me get to the bottom of this it would be deeply appreciated!

 

[Nylundarn]

Do you know why the old battery was in need of changing? If you have a multimeter there is some troubleshooting you could do. Often with these bikes the battery doesn't really charge on idle, it needs higher RPM. Did you charge your new battery before throwing it in? If not, the combination of new not fully charged battery and many startups on idle could have drained it.

I would do this :
1. Charge battery
2. install it and put voltmeter on it
3. read value
4.start bike
5.read value at idle
6.read value at higher RPM

For the battery to even charge, you need 13-14 volt minimum.