Half wave rectifier

[djohns]

Please don’t beat up on me for this topic! I have posted on other small bike forums without any luck. I know there are contributors here whose knowledge transcends the 72/77/95 bikes.
Old problem, insufficient lighting power. The S65 has a half wave selenium rectifier and no regulator. It appears that the lighting coil is half wave also based on the fact that the end of the winding (daytime shunted and nighttime full coil) are grounded to frame. Based on schematic on S90 its coils don’t go to ground. Daytime full wave coil wire to bridge rectifier with common to rectifier, nighttime full wave coils to switch for lights and “excess” 🤣 to rectifier. Am I correct in my observation? If so can the half wave lighting coil be made a full wave by clipping the ground and rerouting to a full wave rectifier/regulator like the S90 setup? Anyone doing this conversion? YouTube video shows a GY?? Scooter engine with half wave alternator converted to full wave by clipping grounded coil and rerouting to new full wave rectifier with regulator. Full wave is more efficient than half wave!
Many thanks to those who share their knowledge, I will gladly take some heartache over posting this here to find an answer. This site has been helpful as I try to work my way through my 35 other Hondas.

[Tim Allman]

I was about to "correct" you and tell you that it's really a full wave rectifier but I'll be damned, after looking at the wiring diagram I see that it really is half wave!

Wow. Honda really went cheap on this model. Half wave rectification is very wasteful but it may be that the battery cannot handle the greater charging current from a full wave circuit which will be a bit less than twice what it is now.

Normally the generator coils are not grounded so the AC side is a circuit separate from everything else. It will take a bit of thinking and drawing over coffee to sort this out. Offhand, I think your plan might well work but I'm not sure. I'll get back to this unless someone else figures it out.

[Tim Allman]

I have found a wiring diagram here. If you download it you can get a higher resolution copy.

Questions.

1. Is this the correct wiring diagram?
2. What do you mean by lighting coil? Is it the generator coil on the left side in the diagram?
3. Do you know what is connected to the rectifier with a white wire? It is labelled (Y ... tube).
4. More to follow probably.

Tim

[djohns]

Yes Tim, that is the correct schematic for mine except for the winkers that we weren’t required to have here in ‘65. Under the flywheel there are two coils, the one on the right is the primary supplying power to the ignition coil ( no batt required to run). The coil on the left is the “lighting coil”. Operations as per key switch diagram. Since I have sufficient current at low rpm’s to generate good spark I believe my magnets are good. The selenium rectifier is half phase due to only one plate vs multiple plates on the larger C72,77,95’s. My question is since the coil, actually both coils, are grounded does that make them half wave producers? See S90 schematic for comparison of half and full wave generation. Many remember having poor lighting on these small bikes at low rpm’s as the lighting is AC and rpm dependent. Would it benefit from going full wave current ? On a side note say hello to my cousins there in Ingersoll/Brantford area. Both mom and dads families were from the area. Beautiful, friendly country when I was doing family research there.

[Tim Allman]

My question is since the coil, actually both coils, are grounded does that make them half wave producers? See S90 schematic for comparison of half and full wave generation. Many remember having poor lighting on these small bikes at low rpm’s as the lighting is AC and rpm dependent. Would it benefit from going full wave current ? On a side note say hello to my cousins there in Ingersoll/Brantford area. Both mom and dads families were from the area. Beautiful, friendly country when I was doing family research there.

Thanks for the answers. I have to say that this is the weirdest way of wiring up a motorcycle that I have seen although I have to admit that my experience is limited. The ability to run without a battery is certainly nice.

I didn't think about whether the generator produces only half waves. I doubt it though simply because there is a rectifier. It wouldn't be needed if the generator produced what could be referred to as pulsed DC. As for the grounding of the coils, this is just a convenience. The frame is being used as a common conductor and eliminates a lot of wiring. In your case both the ignition and lighting etc. circuits both use the frame without interfering with each other.

Could you describe how the magnets are arranged? I haven't been able to find a picture of the inside of the rotor. Also, do they alternate in polarity? You can check this with a compass. Just don't get it closer to the magnets than necessary.

I spent some time this morning going over the wiring diagram. I think your idea will work if the generator produces good old AC. You mention the lighting as being AC but I think not. It is in the circuit with the rectifier and current flows only one way through a rectifier (or diode). If the light pulses at idle I'm not surprised.

I'll have another look tomorrow at my favourite coffee shop as I realise that I still have a couple of things to figure out. I don't know if the engineer that designed the wiring was a drunk or a genius. It's very strange.

Others on this site have installed rectifier-regulators from garden tractors and other things with small engines. This seems a reasonable thing for you to do, the first being that selenium rectifiers aren't great to start with and they have shelf lives. A new rectifier would use silicon diodes which work better in every way and would improve your lighting greatly. The regulator would ensure that the battery isn't overcharged.

Funnily enough, my parents were from Brantford but moved to London just before I arrived on the scene so that's where I grew up. My father worked for Massey-Ferguson in Toronto, Brantford and London for many years. Sadly, I don't know anyone in the area anymore, including your cousins.

[djohns]

If you have time look at a YouTube video by Antilaakeri “6 coil stator full wave conversion-single phase charging”. This is like the S65, and other small bikes system only with one coil instead of the array of six. Note coils to ground in diagram with shunt +- midway. Diagram after conversion shows no grounded coils. Can’t seem to get links installed here for you. You should see another video about GY6 conversion with more detail. Hoping we can get more people, say LM , to comment here. I’ve exhausted my buddies knowledge here to the point of giving them headaches! Have a nice weekend

[deuce_7]

I have access to a complete Honda Workshop Manual for Honda 65 series and Honda 50 series models. Published in August 1966. It's a large file (50+ MB) so it would have to be emailed. The workshop manual has several pages discussing the charging system and selenium rectifier, including graphs, photos, diagrams, and schematics.

This forum site accepts photo files only.

I can email the manual to an address you provide.