1980 Honda CB650 - Battery won't recharge on the road

I have a 1980 Honda CB 650, and the battery is fairly new, but it does not hold a charge. The bike starts up great after I leave the battery on a trickle-charger over night, but after riding for a while, it'll be completely dead. I'm guessing this is an alternator issue, and I just wanted to get some confirmation on that. Also, if it is an alternator issue, any advice on where I can purchase a new one?


Thanks!


HazMatt

its your rectifier!

or regulator or stator, or broken lead or........

Grab a shop manual and start checking resistances on the alternator. Then run the bike at idle with alternator not connected and check output voltage on the AC setting. If it generates say 50 or 70 volts AC, it's probably the regulator or rectifier.

Test before throwing parts at it.

Ok thanks, I'll run some tests and see what I come out with.

Also, the idle is all over the place. By adjusting the idle screw, I've gotten it to remain at around 2000 rpms, but it'll slowly fall, until when it gets to around 1000rpms it'll just die. I have to keep revving it at stop-lights so that it doesn't die on me. I'm assuming this is a carb issue. I'm planning on getting a carb kit and cleaning it out, but let me know if there's anything else I could look at that might remedy the problem.

Thanks!

check the ohms across the rings on the rotor, should not be less that 4.3, if so it's bad and won't charge.

Ah, my friend had this problem with his 650 '81 (I think it's an 81). Same thing... finally managed to resolve it though. Rectifier I believe.

HazMatt said:

Ok thanks, I'll run some tests and see what I come out with.

Also, the idle is all over the place. By adjusting the idle screw, I've gotten it to remain at around 2000 rpms, but it'll slowly fall, until when it gets to around 1000rpms it'll just die. I have to keep revving it at stop-lights so that it doesn't die on me. I'm assuming this is a carb issue. I'm planning on getting a carb kit and cleaning it out, but let me know if there's anything else I could look at that might remedy the problem.

Thanks!

Click to expand...

Airbox boots are cracked, air leaking. but for sure it'll need a cleaning

i was having a similar issue, dead battery after a few rides. my headlight would dim if i wasnt reving the bike and dim more if the brake or turn signal was on. the battery wasnt getting enough charge or enough power to run everything on the bike. checked and replaced a bunch of connections, tested everything stator rectifier and regulator, tried different ones... and in the end it was a loose ground. 3 grounds on the bike one is the 2 nuts in the headlight bucket. 1 in by the coils to the frame. the next is the battery and i believe one in the back by the fender. check them make sure they are tight. mine was by the coils. tightened it and im having no problems and charging again. do yourself a favor and check them first. if you know how to use a multimeter you can save yourself some trouble..not saying this it what it is, but i wished i had checked the easy shit first