Garrett411
CB750 Member
Hey Ya'll
First post on here as i am working on a friends 1981 CB750c for him.
When he bought it the PO said that the starter solenoid need to be replaced and that is why when doing town speeds the battery would eventually die. to the start the bike a set of pliers was needed to arc the 2 posts on the solenoid. So then we replaced the solenoid and the new one came with a 15 Amp fuse which burnt right away, replaced that with a 40 and the bike now will start with the switch. At that time we also replaced the battery. Rode the bike around a few times and eventually would die because of a drained battery. I then took the stator cover off and tested the two rotor strips (ground on battery disconnected) with the switch on and off testing the strips alternatively with the multimeter. Each time it measured around 4-6 ohms at first and the would climb higher after a while. This from what i have read is the kind of thing i should be experiencing with these measurements. So i concluded that i must be the rectifier/regulator. With the bike idling the battery would stay about the same reading 12V about, running about quarter throttle to try and get a charge it would only go up a few hundredths of a volt which doesn't seem like enough. I was expecting around 13'ish. So we replaced the old and im assuming stock regulator/rectifier with a new one. We also replaced the flasher with a new one that i had laying around. The bike will run for a 20 mile highway drive, maybe more starting with 12-12.5 volts, maybe a bit more. But once we get back to town and if we hit traffic or stop lights it sometimes will die and need to be jumped and charged.
Long story short im just wondering what ya'll think of this? I personally just built an XS650 cafe and have no experience with these Cb's. Thinking the problem could still reside in the rotor? Brushes maybe? Any advice is appreciated!
First post on here as i am working on a friends 1981 CB750c for him.
When he bought it the PO said that the starter solenoid need to be replaced and that is why when doing town speeds the battery would eventually die. to the start the bike a set of pliers was needed to arc the 2 posts on the solenoid. So then we replaced the solenoid and the new one came with a 15 Amp fuse which burnt right away, replaced that with a 40 and the bike now will start with the switch. At that time we also replaced the battery. Rode the bike around a few times and eventually would die because of a drained battery. I then took the stator cover off and tested the two rotor strips (ground on battery disconnected) with the switch on and off testing the strips alternatively with the multimeter. Each time it measured around 4-6 ohms at first and the would climb higher after a while. This from what i have read is the kind of thing i should be experiencing with these measurements. So i concluded that i must be the rectifier/regulator. With the bike idling the battery would stay about the same reading 12V about, running about quarter throttle to try and get a charge it would only go up a few hundredths of a volt which doesn't seem like enough. I was expecting around 13'ish. So we replaced the old and im assuming stock regulator/rectifier with a new one. We also replaced the flasher with a new one that i had laying around. The bike will run for a 20 mile highway drive, maybe more starting with 12-12.5 volts, maybe a bit more. But once we get back to town and if we hit traffic or stop lights it sometimes will die and need to be jumped and charged.
Long story short im just wondering what ya'll think of this? I personally just built an XS650 cafe and have no experience with these Cb's. Thinking the problem could still reside in the rotor? Brushes maybe? Any advice is appreciated!