Topic: 1973 CB550F - RECTIFIER/REGULATOR PROBLEMS - HELP

[ValleBR]

Hi. A friend of mine is experiencing problems with the rectifier/regulator of his '73 CB550F. He doesn't get enough voltage at idle revs and this has been damaging his battery. He came across this forum and asked me to help him with the messages (since he doesn't speak English).
Dave500 provided some interesting information on using a Bosch RE57 rectifier to solve this problem (in a post dating back to 2011). I've written to him, but decided to post this issue here to see whether someone could help somehow as well.
We live in northern Brazil (the Amazon) and the climate here is hot and very humid. Our city is not big and there are too many traffic lights here, thus preventing him to ride at constant speeds and relatively higher rpm for more than 200 meters!!! He has lost several batteries over the past 10 years.
So, we appreciate whatever help we can get from any of you.
Best.

[calj737]

Valle - these bikes will always operate in a charging deficit when the engine speed is under 2,000 RPMs. Basically, you have a few options:

- Install a switch to turn off the headlight in traffic
- Perform a complete maintenance of the entire electrical harness, cleaning each and every connector, ground, and terminal.
- Insure the wiring is very clean and solid, with no cheap crimps or splices wrapped in tape
- Idle in traffic with the RPMs above 3,000
- Switch to a lower wattage Headlight bulb

It would also be helpful to perform a few tests to confirm his stock units are in fact charging properly. Every rider with these bikes struggles in traffic. But theres no reason at all not to keep the RPMs up, it won't hurt the motor at all.

[ValleBR]

Hi, Cal.
Thanks for replying.
The following is the translation of my friend's replies to your valuable comments/suggestions:
1) Keeping headlight on at all times is mandatory here in Brazil.
2) The entire electrical circuit of the bike has been checked for broken wires, connectors etc. - it's ok.
3) There are no splices or any type of make-shift in the wiring of the motorcyce.
4) The engine overheats if maintained in idle revs higher than 1,500 rpm in our traffic and climate. Engine oil deteriorates faster, clutch problems etc.
5) I'm using LED headlight bulb to reduce wattage demand.

He says he is really in for trying to buy that RE57 reg that Dave500 shows in his 2011 post. He believes it would be the best solution for this charging deficit at lower rpm.
Do you have any suggestion on where He could buy that regulator/rectifier?

"I know it's complicated to ask you guys for that, but I'd be very greatful if someone could help me find this rectifier, or a similar one."

Thank you all.

[Bodi]

Tell him to try disconnecting the black and white wires at the regulator and connecting them directly together. That gives 100% full power alternator output (do not leave it like this for riding!). Then see what engine RPM is needed for the battery voltage - on a fully charged battery! - to rise toward 14.5V. If it won't do that at any RPM... then there's a problem with the alternator itself, its wiring, or the rectifier.

No regulator can make more power than is produced with this test. The stock regulator can theoretically equal it. Electronic regulators will always be slightly less, because their switching transistors have a forward voltage drop.

With stock ignition (points) and a lower power load LED headlight (I assume it's less power load?) the bike should charge nicely from 2-3000 RPM and lose voltage relatively slowly at idle.

These are not good bikes for traffic jams or parades. They overheat and discharge the battery when run at low rpm and low speed.

Check all the connectors in the alternator circuit for corrosion and overheating. There are connections under the engine side cover in these wires - often a problem area!